The Operator`s Guide to Electrical Safety Compliance

The Operator`s Guide to Electrical Safety Compliance
The Operator’s Guide to Electrical Safety Compliance Testing
Most people who design, build or sell electrically powered products, sub-assemblies or
components are unfamiliar with testing the electrical safety of their products.
Manufacturers of testing instruments and the agents responsible for establishing test
procedures are sometimes at a loss to explain the how and why of a test and the true
meaning of the test results. Some people, when faced with the challenge of performing
a test, become uneasy at the thought of working with a high-voltage system.
Associated Research, Inc. developed this booklet to address these concerns and to clarify
the necessity of electrical safety tests, identify what information can be gained from
them, and learn how to apply the results properly so that all electrical systems operate
safely and efficiently.
Safeguards to protect test operators and bystanders also will be discussed. We hope to
clarify a complex subject and alleviate concerns about safety, operation and analysis.
If you have any questions or concerns, or if you are interested in having Associated
Research provide educational materials for your company’s test personnel, please give
us a call at 1-800-858-TEST (8378). You can also download technical white papers,
articles and other material for use in training and education directly from our website at
Associated Research, Inc.
13860 W. Laurel Dr., Lake Forest, IL 60045-4546 U.S.A.
Toll-free: 1-800-858-TEST (8378)
Telephone: +1-847-367-4077
Fax: +1-847-367-4080
E-mail: [email protected]
Table of Contents
Introduction: Safety and Reasons to Test Insulation ..............................................1
Safety of the Test Operators and Bystanders ..............................................................2
Suggestions for the Test Station ..............................................................................2
Suggestions for Training the Test Operator ..........................................................2
Suggestions for Test Procedures ............................................................................3
Shock Hazard ............................................................................................................4
Startled Reaction ......................................................................................................4
Human Body Resistance ..........................................................................................4
European Directives ..................................................................................................................5
1. CE Mark......................................................................................................................5
a. What is the CE Mark?......................................................................................5
b. How Does the CE Mark Affect Us? ................................................................5
2. Machinery Directive ................................................................................................5
a. The Machinery Directive 89/392/EEC ............................................................5
b. Machinery Directive Product Safety Standards ..............................................5
c. Test Specified Under EN60204-1 ....................................................................6
3. Low Voltage Directive ..............................................................................................6
a. The Low Voltage Directive (LVD) 73/23/EEC ................................................6
4. Medical Directive ......................................................................................................7
Five Types of Electrical Insulation Tests ........................................................................7
1. Dielectric Voltage-Withstand Tests (Hipot) ..........................................................7
Agency Requirements ......................................................................................7
AC Voltage-Withstand Testing Advantages ......................................................8
AC Voltage-Withstand Testing Disadvantages..................................................8
Techniques of AC Voltage-Withstand Testing ..................................................9
Component Testing ..........................................................................................9
Transformer Testing..........................................................................................9
Appliance Testing ..........................................................................................10
Hot Hipot Test ................................................................................................11
Indications of Electrical Breakdown..............................................................12
Indications of Excessive Leakage Current ....................................................12
500 VA AC Hipot Testing................................................................................12
500 VA Safety Risks ........................................................................................13
DC Voltage-Withstand Testing Advantages ....................................................13
DC Voltage-Withstand Testing Disadvantages ..............................................14
Techniques of DC Voltage-Withstand Testing ................................................14
Indications of Electrical Breakdown..............................................................14
Indications of Excessive Leakage Current ....................................................14
Line Leakage Tests..................................................................................................16
a. Performing a Line Leakage Test ....................................................................16
b. Line Leakage Test Requirements ....................................................................16
c. Correlations Between Hipot Leakage and Line Leakage ..............................16
Insulation Resistance Measurements ..................................................................17
a. Why Measure Insulation Resistance ..............................................................18
b. Motor Testing..................................................................................................18
c. Component Testing ........................................................................................18
Polarization and Ground-Continuity Tests ..........................................................19
Ground Bond Tests..................................................................................................19
Continued on next page…
…Table of Contents Continued
Functional Run Tests
Tests While the DUT is Operating..................................................................21
The Case for Automatic Testing ....................................................................21
Same-Station Safety and Functional Run Testing ..........................................21
Summary ........................................................................................................22
Scanning Matrix Systems......................................................................................................22
Recent Technology Developments ....................................................................................23
Line and Load Regulation ..............................................................................23
No Load Setup of Trip Current and Voltage Output ......................................24
Breakdown vs. Arcing ....................................................................................24
Arc Detection..................................................................................................25
Real Current ..................................................................................................25
Electronic Ramping ........................................................................................27
Patented Ramp-HI ..........................................................................................27
High and Low Current Sense ........................................................................27
Patented Charge-LO ......................................................................................28
Software Calibration ......................................................................................28
Patented CAL-ALERT® ..................................................................................28
Patented SmartGFI ® ....................................................................................28
Enhanced Graphic Liquid Crystal Display....................................................29
Prompt Screens ..............................................................................................29
Patented VERI-CHEK® ..................................................................................29
Automated Testing ....................................................................................................................30
1. Programmable Logic Control (PLC) ....................................................................31
2. RS-232 Interface ......................................................................................................31
3. IEEE (GPIB) Interface ..........................................................................................31
Index ..................................................................................................................................................32
Appendix ........................................................................................................................................32
Glossary of Terms ..................................................................................................32
Associated Research Patents ................................................................................33
Safety Agency Listings ..........................................................................................34
Sample Safety Agency Specifications ..................................................................35
Sources of Additional Information ......................................................................40
©2004 Associated Research, Inc. All rights reserved. No part of this book may be reproduced in any form or by any
means without the express written permission of the publisher.
Printed in U.S.A. 11th edition.
and OMNIA are all trademarks of Associated Research, Inc.
Introduction: Safety & Reasons to Test Insulation
As a woman reached for a dry towel after her bath, she
made contact with her electric clothes dryer and was
electrocuted. The woman acted as a ground path for the
ungrounded dryer supplied with a two-prong plug, and
the dryer’s faulty insulation system caused the woman’s
electrocution. (1)
Many injuries and electrocutions are caused by electrical products with faulty insulation or when a product’s
safety grounding system is defeated. Like the woman
who acted as a ground path for her ungrounded clothes
dryer, a person who uses an ungrounded power drill
while standing on a damp garage floor or another person
who touches an ungrounded space heater when his or her
clothes are wet both run the risk of accidental electrocution if products are not properly insulated.
(Figure 1) Wire 120/240V AC, Single phase
secondary distribution systems
each of those lines is usually ground-referenced independently, and each provides a predictable voltage to
ground. Therefore, any line that contacts a ground path
will allow current to flow.
As manufacturers of products designed for consumer
or industrial use, we cannot prevent product users from
defeating grounding systems, we can only warn them of
the risks. However, we must prevent products with faulty
insulation from leaving our factories.
To protect consumers, manufacturers need to perform
several types of electrical safety tests to ensure that
products, household electric coffee makers and brewing
devices, for example—meet industry standards for
product construction, performance, ratings, markings
and instruction manuals.
The insulation in a product which concerns us most is
that which separates the power line circuit from
everything else—secondary, low-voltage circuits,
isolated power supplies either inside or outside the
product, the shell or case of the product, whether
groundable or not, etc.
But only one test, the Dielectric Voltage-Withstand
test, is required for every appliance shipped. (2)
This insulation prevents current from an ordinary
household outlet, an almost unlimited power source,
from becoming hazardous by finding a ground path with
something that is not meant to be a ground path.
Manufacturers have additional reasons for insulation
testing. Not only do they want to prevent faulty
components from being installed in their products, but
they must also catch workmanship defects in assemblies
before they are installed. The earlier a defect is detected,
the less a manufacturer will have to spend reworking the
product. Many manufacturers are performing tests to
ensure product quality for ISO compliance. Other manufacturers may test to protect themselves from product
liability suits. However, as a rule, user safety always is
the greatest concern.
Current flows into any available ground path because
most power distribution systems are ground-referenced.
When power is generated, one side of the generator
output is connected to a ground at the point of output.
Every time power is transformed from one voltage to
another, one side of the secondary is grounded. In
household power distribution, all neutral wires in a house
are connected to a ground connection at a single point
(See Figure 1). Some power is distributed ungrounded,
so that the system will tolerate one fault to ground
without shutting down. This typically is high-voltage
intermediate ground distribution, not directly accessible
to the end user.
(1) Mazer, William M., Electrical Accident
Investigation Handbook, Electrodata, Inc.,
Glen Echo, Md., 11/83 sec.
(2) UL Standard 1082 for Household
Electric Coffee Makers and Brewing-Type
Devices, Underwriters Laboratories, Inc.,
Northbrook, Ill. 2/81
Three-phase and 120/240V systems also provide
power across independent ungrounded hot lines. But
Safety of the Test Operators & Bystanders
Suggestions for the Test Station
consider two switches (palm buttons) that must simultaneously be actuated. Space the switches far apart. You
may have to use a separate (anti-tie down) relay or
control. Never make any connection to the instrument
that could energize the high-voltage independently, i.e.,
without the control of the operator unless the test application is fully automated.
Choose an area away from the mainstream of activity,
where employees’ normal routines will not be interrupted. The area must be clearly marked, minimum
clearances of 3 to 8 feet must be maintained around any
exposed live parts to protect unqualified persons.
Shields, protective barriers or protective insulating
materials shall be used to protect each employee from
shock, burns or other related injuries while the employee
is working near exposed, energized parts which might be
accidentally contacted.
Dielectric Voltage-Withstand instruments must be
connected to a good ground. Be certain that the power
wiring to the test bench is properly polarized and that the
proper low-resistance bonding to earth ground is in
place. Some instruments use monitor circuits that check
the connections to the power line and ground. The
warning lights on these “line monitors” are designed to
show such problems as incorrect wiring, reversed
polarity or insufficient grounding. If you see anything
other than an ‘OK’ signal, turn off and unplug the
instrument immediately. Do not use it until the wiring
is repaired.
Mark the testing area with clearly posted signs that
Set up the test station
so that the power,
except lights, can be cut
off by a single switch.
Position the switch at
the perimeter of the test
area and label it clearly.
Keep the testing area clean and uncluttered. Make sure
the test operator (and any observers) knows exactly
which product is being tested, which is waiting to be
tested and which has already been tested. Provide considerable bench space around the product being tested.
Place the instrument in a convenient location so that the
operator does not have to reach over the product being
tested to activate or adjust the instrument.
Instruct employees that in an event of an emergency,
the power must be shut off before anyone enters the test
area to offer assistance.
Use only a non-conducting table or workbench for
tests. Remove any metal objects that are between the test
operator and the products being tested. Ground all other
metal objects that are
not in contact with
the DUT. Do not
leave them “floating.”
If small products are
being tested, use a
material, such as
clear acrylic, to
construct guards or an
enclosure during the
test. Fit the enclosure
with an interlocking
switch so that it will
not operate unless the
enclosure is in place. Use insulated safety floor mats in
the test area to isolate the operator from ground.
Suggestions for Training the Test Operator
For safety reasons, it is very important that test
operators are equipped with the appropriate knowledge
to safeguard themselves and others from accidental electrical shock. When training an operator it is important to
make them aware of potential hazards and how their
actions can create potential hazards. Is is important to
make sure that the test operator understands the
1. A test operator should have a basic understanding of
electricity, voltage, current, resistance, and how they
relate to each other. They should also understand
conductors, insulators and grounding systems.
2. A test operator should have a working knowledge of
the test equipment, the tests that are being performed,
and the hazards associated with the tests as well as the
circuits that are being energized.
If the instrument can be operated by remote switches,
3. A test operator should understand the approach
distances and corresponding voltages to which they may
be exposed.
voltage lead from the DUT before the test is complete
can leave the DUT charged. When you are performing a
Hipot test you are testing the insulation between two
conductors which is essentially a capacitor. This
capacitor can act as a storage device and hold a charge
even when performing an AC test. If the circuit is
opened at the peak of the applied voltage then the DUT
could, even under an AC test, hold a charge. When the
test is allowed to finish and the voltage is reduced to
zero the charge is dissipated through the impedance of
the high voltage transformer of the Hipot tester. Most
DC Hipot testers today employ an output shorting
device to discharge the DUT, but the Hipot must remain
connected to the DUT throughout the test cycle.
4. A test operator should be trained to understand the
specific hazards associated with electrical energy. They
should be trained in safety-related work practices and
procedural requirements as necessary to provide
protection from the electrical hazards associated with
their respective job or task assignments. Employees
should be trained to identify and understand the relationship between electrical hazards and possible injury.
5. A test operator should understand that the three
primary factors that determine the severity of electric
shock are:
A. The amount of current flowing through the body
B. The path of the electrical current through the body
C. The duration or length of time the person is exposed
You should emphasize to the operator the range of
output voltage as well as the correct voltage to be used
for the products being tested. Explain how much current
the instrument can supply, and that current, not voltage,
injures or kills.
6. A test operator should know that the human body
responds to current in the following manner:
A. 0.5 to 1 mA is the perception level
B. 5 mA a slight shock is felt, a startle reaction is
C. 6 -25 mA for women and 9 -30 mA for men can
produce the inability to let go
D. 30 - 150 milliamps results in extreme pain, respiratory arrest, ventricular fibrillation and possible death
E. 10 Amps Cardiac Arrest and severe burns can occur
In addition, operators should be warned that defeating
any safety systems or allowing unauthorized personnel
into the testing area are serious breaches of testing
procedure safety and will result in severe penalties,
including removal from a testing job. Lastly, warn
operators not to wear jewelry, especially hanging
bracelets or necklaces, which could become energized.
Modern test instruments with microprocessor control
offer password-protected modes of operation, allowing
the operator to access only certain functions. These
features should be used whenever applicable. If operators
are not restricted, they should be trained not to adjust
controls during a test and not to change test setups
without proper authorization.
7. A test operator working on or near exposed energized
electrical conductors or circuit parts should be trained
in methods of release of victims from contact with
exposed energized conductors or circuit parts.
8. A test operator should understand that the test
instrument is a variable voltage power source and the
current will flow to any available ground path. They
should be aware that contacting the device under test
(DUT) during the test can result in a dangerous shock
hazard under certain conditions.
Suggestions for Test Procedures
Verify that the high-voltage output is off before
making connections.
Connect the low return side of the instrument first.
Securely connect the clip lead to the exposed metal parts
being tested.
9. A test operator should understand that if the return
circuit is open during the test then the enclosure of the
DUT can become energized. This can occur if the
return lead is open or the operator lifts the return lead
from the DUT while a test is in process.
If you use a clip lead to connect the high-voltage side
of the instrument, handle the clip only by its insulator—
never touch the clip directly.
10. A test operator should be made aware of the
importance of discharging a DUT. Lifting the high
If using an instrument with a panel mounted
receptacle, first connect the return clip lead, then plug the
product’s cordset into the instrument. It should be
absolutely clear to which product the cordset belongs.
• In the case of an emergency, or if problems arise,
turn off the high-voltage first.
When using a test fixture, be certain that it is properly
closed and that all guards are in place. The test fixture
should be interlocked with switches so that the test
cannot begin if it is not in place.
• Properly discharge any DC-tested product before
touching or handling connections.
Double-check the connections before testing. Provide
enough clear space around the product being tested.
The severity of shock received by a person who
contacts an electrical circuit is affected by three primary
Follow the high-voltage lead from the instrument to the
product and keep the lead on the bench running as close
to the product as possible. Avoid crossing test leads.
Neatly coil any excess lead halfway between the
instrument and the product.
1. The amount of current flowing through the body.
2. The path of the electrical current through the body.
3. The duration or length of time the person is exposed.
Shock Hazard
Burns are the most common form of shock related
injury. Any person who is exposed to voltages in excess
of 50 volts is at risk of being injured from an electrical
shock. Currents as low as 50 mA can cause an irregular
heart beat which is known as fibrillation, which can
cause the heart to stop the pumping action.
Develop a standard test procedure and follow that
procedure throughout the test.
Check all instrument settings before beginning the test.
Test leads should also be checked periodically for
excessive wear of the insulation or openings in the
Startled Reaction
UL and ANSI conducted experiments in the 1960’s to
determine how the human body responded to different
current levels. Tests were run using a 120 volt 60 Hz
source. They determined that on average 0.5 mA of
current is the perception level that can produce a startled
reaction. Higher levels of current in the range of 5 to 10
mA start to produce an inability to let go. The electrical
current causes a paralysis where you cannot release a
handgrip on the circuit. Currents in the range of 20 to 40
mA between the extremities makes the muscles contract
painfully, making breathing difficult leading to asphyxiation. Current levels in the 40 to 70 mA range lasting for
1 second or longer causes Ventricular Fibrillation that is
frequently fatal. Further increasing the currents greater
than 70 mA causes electrical burns and cardiac arrest.
Never touch any of the cables, connections or product
during the test.
Have a “hot stick” on hand when doing DC testing. (A
“hot stick” is a non-conducting rod about two feet long
with a metal probe at one end, which is connected to a
grounded wire.) If a connection comes loose during the
test, use the “hot stick” to discharge any surface that
contacted the instrument's hot lead—simply turning off
the power is not sufficient.
After the test, turn off the high-voltage. Discharge DCtested products for the proper length of time. Products
tested with AC do not need to be discharged. This is
further explained on pages 11 and 12.
Human Body Resistance
In summary, for safe high-voltage testing, remember to:
The human body on an average has about 1000 to 1500
ohms of resistance to the flow of electrical current. The
outer layer of the skin provides the largest percentage of
the body’s electrical resistance. The amount of resistance
the skin provides varies widely. Dry thick skin provides
a much higher resistance than moist soft skin or skin
which may have a cut or an abrasion. The parts of the
body that conduct the electricity the best are the blood
vessels and nerves. Therefore when a person receives a
• Keep unqualified and unauthorized personnel away
from the testing area.
• Arrange the testing area out of the way of routine
activity. Designate the area clearly.
• Never touch the DUT or the connections between
the DUT and the instrument during a test.
severe electrical shock many times internal injuries may
result. The skin, like any insulator has a breakdown
voltage at which it ceases to act like a resistor and is
simply “punctured” leaving only the lower resistance
body tissue to impede the flow of current in the body.
This voltage will vary with the individual, but is
normally in the area of 600 volts (See Figure 2).
• Hand to hand 1000Ω
• 120 volt
• Formula I = E/R
• 120/1000 = 0.120 amps or 120 mA
(Figure 2)
European Directives
has to prove that its product has not been the cause of
the damage.
It is an indication of compliance to the European
Union directives, which are currently in force.
Compliance to the European directives ensures that
the product complies with the minimum safety
requirements and that damage claims can be limited.
Machinery Directive
Directives are legal requirements that the manufacturers must fulfill to get products into the European free
market. The aim of the directives is to remove the
technical barriers to trade and to permit free access to the
total European market.
The Machinery Directive 89/392/EEC
Inception Date 1/1/90
Enforcement Date 1/1/95
The directive applies to machinery which is described
as (1) linked parts or components, at least one of which
moves with the appropriate actuators, control and power
circuits, joined together for a specific application, in
particular for processing, treatment, moving or
packaging of a material and (2) an assembly of machines
which in order to achieve the same end, are arranged and
controlled so that they function as an integral whole, and
(3) interchangeable equipment modifying the function of
a machine which is supplied for the purpose of being
assembled with a machine (or series of machines or with
a tractor) by the operator himself in so far as this
Harmonized standards (not the directives) set out the
technical provisions required for compliance to
European safety requirements.
Many products must now be produced and tested to
standards that did not previously apply. More
customers are now required to test products to strict
safety standards in order to be able to sell their
products into the European community.
Under the new European product liability directive
the consumer does not have to prove that a product has
caused damage. The manufacturer is liable for damage
caused by a defect in its product. The manufacturer
Machinery Directive Product Safety Standards
EN (European Norm standards) are based on IEC
(International Electro-Technical Commission) standards
which are broken down into:
maintained and used in applications for which it
was made.”
• (Type a) or basic standards such as EN 292, 292-1, 2922, EN 1050; safety of machinery/terminology. These are
basic standards that give the basic concepts and principles for the design and the general aspects that apply to
all machinery.
Products with a voltage rating of between 50 and 1000
volts for AC and between 75 and 1500 volts for DC must
comply with these unified standards if the products are to
be marketed in the EU after January 1, 1997.
Harmonized product safety standards are to be drawn
up by common agreement between the bodies notified by
the member states and shall be kept up to date in the light
of technological progress and the development of good
engineering practice in safety matters.
• (Type b) or generic standards (group safety standards)
dealing with one safety aspect or one type of safety
related device that can be used across a wide range of
• (Type c) or product specific standards giving detailed
safety requirements and risk categories applied for a
particular machine or group of machines, EN 201,
injection molding machines or plastics.
Some examples of harmonized safety standards are:
• Continuity of the protective bonding circuit
Minimum of 10 amps at 50 Hz for 10 seconds. The
maximum resistance is based upon the conductor size of
the protective bonding circuit ranging from 0.100 to
0.330 ohms.
• Insulation Resistance test
500 volts DC between the power circuit conductors and
the protective bonding circuit. The insulation resistance
shall not be less than 1 megohm.
Each standard provides a series of tests with specific
test parameters and limits appropriate to the category
of the equipment covered. Some examples are:
• Voltage test or Dielectric Withstand test
A period of at least 1 second between the conductors of
all circuits and the protective bonding circuit. The test
voltage shall have a value of twice the rated supply
voltage of the equipment or 1000 volts, whichever is the
greater value at a frequency of 50 Hz and be supplied
from a transformer with a minimum rating of 500 VA.
Low Voltage Directive
All the tests are designed to ensure safe operation of
the equipment by the user, some of the tests also
specify abnormal operational tests to predict the
performance of the equipment should accidents or
faults occur. Many of the specifications do not specify
different tests for production vs. design. There are
some proposed standards now being considered to
establish production line tests such as EN 50116.
The Low Voltage Directive (LVD) 73/23/EEC
Inception Date Feb. 1973
Enforcement Date 1/1/97
The low voltage directive states; “the member states
shall take all appropriate measures to ensure that the
electrical equipment may be placed on the market only if,
having been constructed with good engineering
practices in safety matters in force in the community,
it does not endanger the safety of persons, domestic
animals or property when properly installed and
The technical construction file and the declaration
of conformity requires the manufacturer to compile
the conceptual design and manufacturing drawings as
well as components and sub assemblies. Full design
calculations and test reports are also required. In
addition, the manufacturer must take all measures
necessary to ensure the manufacturing process is in
compliance and maintain technical documentation for
10 years after the last product has been manufactured.
Based upon these requirements the manufacturers
must perform checks on their products at random
intervals and be able to document the test results.
appliance, material or other article, whether used
alone or in combination, including software necessary
for the proper application, intended by the manufacturer to be used on human beings for the purpose
of: diagnosis, prevention, monitoring, treatment or
alleviation of a disease, an injury or a handicap.
Investigation, replacement or modification of the
anatomy or a physiological process. Control of
conception and which does not achieve its principal
intended action in or on the human body by pharmacological, immunological or metabolic means,
but which may be assisted by such means. All
devices being put on the market in the EU after June,
1998 must bear the CE mark. IEC 601-1 covers
the general requirements for safety for medical electrical equipment.
Medical Directive
The Medical Devices Directive 93/42/EEC
Inception Date 1/1/95
Enforcement Date June, 1998
This directive is one of three medical directives.
This directive covers any instrument, apparatus,
Five Types of Electrical Insulation Tests
Dielectric Voltage-Withstand Tests (Hipot)
The Dielectric VoltageWithstand test, or Hipot
(High Potential) test, is
designed to stress insulation
far beyond what it will
encounter during normal use.
The assumption is that if
the insulation can withstand
the much higher voltage for a
given period of time, it will
adequately at its normal
voltage level—thus the term
“voltage withstand test.”
(Figure 3)
Agency Requirements
Independent and government test agencies—such as
Underwriter’s Laboratories, Inc. (UL), Canadian
Standards Association (CSA), International
Electrotechnical Commission (IEC), British
Standards Institution (BSI), Association of
German Electrical Engineers (VDE), Technische
Überwachungs Verein (TÜV) and the Japanese
Standards Association (JIS)—require Dielectric
Voltage-Withstand testing to verify that a product’s
design meets their standards (design tests). They also
In addition to over stressing the insulation, the test also
detects material and workmanship defects which result in
conductor spacings that are too close.
When a product is operated under normal conditions,
environmental factors such as humidity, dirt, vibration,
shock and contaminants can close these small gaps and
allow current to flow. This can create a shock hazard if
the defects are not corrected at the factory.
No other test can uncover this type of defect as well as
the Dielectric Voltage-Withstand test (See Figure 3).
UL requires that Hipot test instruments meet certain
output voltage regulation specifications to ensure that the
DUT is stressed at the correct voltage.
For one-second tests, the Hipot's output voltage must
be no less than 100 percent and no more than 120 percent
of the specified test voltage.
(Figure 4) OMNIA® Model 8104, 4-in-1
Electrical Safety Compliance Analyzer.
When test voltage is applied for one minute, the
Hipot's meter can easily be monitored to see if the output
voltage has varied. The operator also has enough time to
adjust the output voltage to the correct level if necessary.
require a routine production line test for every product
However, during a one-second test, the Hipot's
voltmeter usually cannot respond quickly enough to
show the operator the test voltage that actually was
Another requirement driving product safety testing is
the need for manufacturers selling products to Europe to
comply with CE regulations.
These regulations call out requirements for performing
a variety of emissions and electrical safety tests.
Associated Research instruments have been tested to
meet the CE regulations allowing our instruments to be
used worldwide. AR instruments also meet the product
safety requirements of EN 61010-1 and are TÜV/GS and
C-UL-US listed (See Figure 4).
Depending on the safety standard, UL wants to ensure
that a Hipot can maintain between 100 and 120 percent
of the required test voltage while connected to an
Adjustable Resistance Bank. The resistance bank has a
maximum resistance of at least two megohms and is
adjustable so that resistance is reduced stepwise in
increments that do not exceed 25 percent of the
preceding value.
Design tests are performed on a product sample and
usually are more stringent than the production line tests
for the same products. AC voltage is specified more often
than DC for these tests. For further details on this, see the
DC testing section on page 13.
Every manufacturer testing to UL specifications is
required to have this resistor bank available for the
UL inspector.
Test voltages are seldom less than 1000V, and for some
products intended to operate at voltages between 100V
and 240V, the test voltage can exceed 4000 volts.
AC Voltage-Withstand Testing Advantages
• Waiting time is not required after applying the test
voltage, nor is it necessary to apply the voltage gradually
unless the DUT is sensitive to a sudden application.
A rule of thumb that most safety agencies use to
determine the appropriate test voltage is to multiply the
DUT’s normal operating voltage by two and add 1000V.
• It is unnecessary to discharge the DUT after
AC testing.
• AC stresses the insulation alternately in both polarities.
Agency requirements also take the product’s intended
usage and environment into consideration. For example,
medical equipment with applied parts that have direct
contact with the patient are tested at 4000 V.
AC Voltage-Withstand Testing Disadvantages
The reactive component of the current (caused by the
product’s capacitance) is often much greater than the real
component (caused by leakage).
Most double-insulated products are subjected to
design tests at voltage levels much higher than the rule
described above.
Unless these two components are separated, the
leakage current can increase by a factor of two or more
without being detected.
The amount of time high-voltage must be applied
during testing is also specified in many UL standards.
The most commonly used times are one second and
one minute.
This point is ignored by some UL standards that
specify the minimum sensitivity of voltage-withstand
instruments in the following way: if the instrument is set
Some instruments incorporate several common safety
tests into a single instrument. Instruments with either 3in-1 capability (See Figure 6) (AC Hipot, DC Hipot &
Insulation Resistance), 4-in-1 capability (See Figure 4)
(AC Hipot, DC Hipot, Insulation Resistance & Ground
Bond), 5-in-1 capability (AC Hipot, DC Hipot,
up as usual and adjusted for a test, and a 120 kohm
resistor is tested instead of the product, then the test
must fail. This means that the maximum permissible total
current (reactive and real) is equal to the test voltage
divided by 120,000 ohms. (The threshold actually is
slightly lower than this value because the current drawn
by a 120 kohm resistor must always cause a failure indication.) Although UL specifies that the total current is
important for safety reasons, the test cannot effectively
detect an abnormally high insulation leakage if it is
masked by normally high reactive current (due to
Many engineers believe that AC voltage at elevated
levels can damage even good insulation. However, the
sheer variety of insulation types and combinations used
make such blanket statements impossible to justify.
(Figure 6) HypotULTRA®III Model 7650 with
graphic LCD readout.
Insulation Resistance, Ground Bond/Ground Continuity
and Functional Run) and 6-in-1 capability, (AC Hipot,
DC Hipot, Insulation Resistance, Ground Bond/Ground
Continuity, Functional Run & Line Leakage) can dramatically simplify test connections and test setups and
provide a fully automated testing sequence.
AC testing, particularly when it is applied for extended
time periods, can degrade certain organic compounds.
Air insulation typically is unaffected, as it is constantly
being replaced by natural convection except in small
sealed spaces.
Component Testing
Once the proper instrument for the job is chosen a
testing plan needs to be developed. Components are
tested by determining which insulation is to be tested and
arranging the test so that only that insulation is stressed.
A common practice is to tie together connections of
circuits which should not be stressed.
Insulation damage can be minimized by selecting the
lowest possible failure threshold, keeping the test voltage
at, but not below, the required minimum, timing the test
accurately and avoiding unnecessary re-testing.
Techniques of AC Voltage-Withstand Testing
Most Hipots have a high-voltage shutoff mechanism to
protect the output transformer. This mechanism also
turns on a failure indication which remains active and
conspicuous until manually reset (See Figure 5). If an
instrument’s current capability is sufficient to test highly
capacitive products, then it also presents a higher safety
risk to the operator. The test connections and DUT must
be handled with extreme care by competent operators,
and unauthorized persons should not be allowed in the
testing area.
For example, suppose the user wants to test a potentiometer. Its dielectric withstand rating is 900V AC for
one minute, either between the resistive element and the
metal shell or between the wiper and the metal shell. Tie
all three terminals (each end of the element and the
wiper) together. The low (ground) side of the instrument
should be connected to the metal shell, and the hot side
to the three terminals. Then perform the test at 900V for
one minute. By tying together the resistive elements you
will apply potential across the insulation rather than the
Transformer Testing
Consider a second example in which a transformer is
tested. While reading the specifications carefully, it is
discovered that the transformer is rated at 1500V AC
primary to secondary, 1500V AC primary to core and
500V AC secondary to core. Tie both leads of the
secondary to the core and to the low side of the
instrument, and tie both leads of the primary together and
to the hot side. Test the transformer at 1500V. This tests
(Figure 5) Hypot®III Model 3665 with manual
reset and audible and visual failure indicators.
transformers with more than two windings. Always try to
connect every winding and the core to one side of the
instrument or the other.
Carefully observe the ratings of every winding to every
other winding and to the core. If no rating is given
between a pair of windings, find out what the rating is, or
connect the pair to the same side of the instrument.
Before testing is begun, and once a combination is
decided upon, review the specifications to be sure that no
ratings will be exceeded.
Make notes as to which specifications will be tested
with that particular combination of hookups.
(Figure 7A)
Do this with each proposed connection combination
and verify that all the desired tests will be made.
Simplify the plan as much as possible, verify again that
no ratings will be exceeded, and then proceed carefully
with testing.
Some fully-automated instruments offer accessories
such as high-voltage switching systems or high-voltage
matrix scanners, which can be programmed to apply
voltage to specific points in any combination. This makes
it easier to test products that may require multi-point
testing such as transformers, motors and components
(See Figure 8).
(Figure 7B)
the first two specifications (See Figure 7A). Then tie both
leads of the primary to the core and to the low side, and
both leads of the secondary together and to the hot side,
and test at 500V. This tests the third specification (See
Figure 7B).
(Figure 8) HypotULTRA® III Model 7620 can be
provided with an optional built-in scanner with
front panel status lights. A separate interconnectable
scanner is also available as an option.
Do not leave windings open at one or both ends during
a test. It is a good idea to connect the core to the low side
of the instrument. If primary to secondary insulation is
being tested, determine which is rated higher to the core
and connect the hot side of the instrument to that
winding. Connect the winding which is rated lower to the
core together with the low side of the instrument and
the core.
Appliance Testing
When testing hard-wired finished products, such as
built-in appliances, one normally will connect the low
side of the instrument to the frame or exposed metal, and
the high side to the line and neutral connections tied
together. Some appliances have both 120V and 240V
circuits, but return them to ground instead of using
isolation transformers. In this case, a break in the
One should take special precautions when testing
connection between the returns of the 120V circuits and
ground is needed before proceeding with the test.
If this cannot be improved, it is advisable to gradually
raise the test voltage to eliminate any overshoot which
might occur with a sudden application of voltage. Do not
start timing any sooner than the point when the voltage
reaches the full specified test voltage.
Turn on all power switches on the appliance for the test
so that all internal circuits are tested. Note that overvoltage should never be applied to the same points where
normal line voltage is applied. Instead, the instrument is
connected to the exposed metal parts of the product from
all the line and neutral circuits tied together.
The Hot Hipot Test
Some circuit designs utilize relays to interrupt or
apply power to other circuits. If only one side of the
line is opened by the relay the complete circuit is still
tested as voltage is applied to both conductors. Some
products especially those that are powered from a 220
volt source use relays that open both sides of the line.
Cord-connected finished products are tested in much
the same way. Connect the exposed metal parts of the
product to the low side of the instrument. If a test is being
performed on double-insulated products, the product
may need to be wrapped in
foil and the returns
connected to the foil.
Connect the line and
neutral terminals to one
another and to the hot side of
the instrument. Again, 240V
products with some 120V
circuits returned to ground
will require breaking that
return-to-ground connection
before testing. Dielectric
Withstand testers with builtin receptacles or external
receptacle boxes greatly
simplify testing of cordconnected products. The
receptacle box for the hipot
test is wired specially, the
line and neutral sides of the
receptacle are connected to
one another and to the
instrument's hot side.
(Figure 9) Hot Hipot Test
When both sides of the line are opened the circuits
controlled by the relays are not tested. In order to test
these circuits the relays must be closed manually. If the
relays cannot be closed these circuits must be bypassed
to perform the test. However, when testing a completed
product these two options are not always available.
Depending on the individual relay, it may not be
possible to manually close the contacts. In addition it
may be very difficult and time consuming to jumper out
the circuits to be tested. The operator must also
remember to remove all the jumpers when the test is
complete. Therefore manufacturers are looking at more
efficient testing solutions.
Because a Ground Continuity test often is required
in addition to the Dielectric Withstand test, the receptacles ground connection frequently is used to check
ground continuity.
Although the pin usually is grounded during Dielectric
Withstand tests, it does not substitute for the clip lead
ground connection to the exposed metal of the product,
which should be made before plugging the product into
the instrument. Cord-connected products also should
have all power switches turned on during a test.
If a product usually breaks down at a voltage just
above the required test voltage, the product was probably
designed with a small margin for safety.
A unique method of performing the Hipot test is to
run the test while the DUT is powered up. This is
known as a “Hot” Hipot test. The Hot Hipot Test allows
the operator to close or energize circuits controlled by
relays. This is accomplished by utilizing an isolation
transformer to power up the DUT. The Hipot voltage is
then applied between one leg of the energized circuit
and the case of the DUT. An isolation transformer must
be used to isolate the incoming power supply voltage
from earth (see figure 9). This is required as most
power systems are ground referenced, and the return
circuits on most Hipot testers are also at ground or near
ground potential. If the isolation transformer is not
used, line current can flow back through the return
circuits of the Hipot resulting in damage to the test
instrument and creating a potential shock hazard. The
return circuits of the Hipot testers are designed to
handle a very small current usually in the order of
milliamps of current, while the power source would be
capable of supplying hundreds of amps of current. Not
using an isolation transformer could also result in false
failures during the Hipot because the neutral side of the
line is referenced to earth.
to establish a sensitivity setting for Hipot testers. The
standard states the following: “When the test equipment
is adjusted to produce the test voltage and a resistance of
120,000 ohms is connected across the output, the test
equipment is to indicate an unacceptable performance
within 0.5 seconds. A resistance of more than 120,000
ohms may be used to produce an indication of unacceptable performance, if the manufacturer elects to use a
tester having higher sensitivity.”
Indications of Electrical Breakdown
Dielectric breakdown may be defined as the failure of
insulation to effectively prevent the flow of current,
sometimes evidenced by arcing. If voltage is raised
gradually, breakdown will begin at a certain voltage level
(where current flow is not directly proportional to
voltage). When breakdown current flows, especially for a
period of time, the next gradual application of voltage
often will show a breakdown beginning at a lower
voltage than initially measured.
In the type of instrument which has failure and highvoltage shutoff circuitry, excessive leakage will trigger
the failure system.
The maximum leakage current is dependent upon the
test voltage, therefore the leakage current trip setting will
vary depending upon the circuit or product being tested
and the capacitance of that product.
Indications of Excessive Leakage Current
Most instruments have adjustable thresholds for
leakage, below which they will not indicate a leakage
failure. In an instrument with a high-reactance type of
transformer, excessive leakage often is indicated by a
separate leakage light, and the voltmeter reading can
drop to near zero.
Models with current meters will indicate excessive
leakage current. Excessive leakage current may be
defined as AC or DC current flow through insulation and
over its surfaces and AC current flow through a capacitance (where current flow is directly proportional to
voltage). If breakdown does not occur, the insulation and
capacitance are considered a constant impedance. Most
instruments have adjustable thresholds for leakage below
which they will not indicate a leakage failure.
The following conditions can sometimes indicate
breakdown of the device under test.
Additionally, some models have a display that will
provide details on the type of failure as well as a meter
memory system that will hold the last voltage and current
readings displayed before failure of the DUT.
1. Arcing
2. Erratic kilovoltmeter
3. Breakdown or arc lamp may flicker
However, newer instruments which have line and load
regulation are designed to maintain a constant output
voltage, therefore voltage variations as a result of the
arcing condition may not exist. Digital metering may not
have a fast enough sampling rate to display voltage variations and the response time of some analog meters may
be too slow. The sensitivity settings of Hipot testers vary,
some may not detect high impedance arcing conditions,
some may only respond to maximum current levels.
Many standards do not specify a maximum allowable
leakage current. UL introduced what is referred to as the
120 kohm requirement in 1983 on some standards to try
(Figure 10) Hypot®II Model 4500D 500 VA
AC Dielectric Withstand Tester.
setting. The applications most commonly requiring a
Hipot with a 500 VA rating are those in which an AC
Hipot voltage must be applied to a highly capacitive load.
Applying an AC test voltage to a capacitive DUT causes
a flow of capacitive leakage current, which can have a
dramatic effect on the total leakage current that the Hipot
measures; the capacitive leakage current is often much
greater than the current that flows due to resistive
leakage, and in itself could trigger the need for a 500 VA
500 VA AC Hipot Testing
Several years ago, the European Union began
enforcing requirements for compliance safety testing of
most electrical products sold into the European
Community. These requirements were established to
safeguard the health of both consumers and workers and
to protect the environment; the intention was to provide
a set of harmonized standards for product-safety and
quality testing that would be accepted by all EU member
states. Once it has met the test requirements, a product
must be affixed with a CE approval notification before it
can enter the European market.
500 VA Safety Risks
Unfortunately, the 500 VA output capacity poses a
considerable safety risk for the Hipot operator: the higher
the current output of the Hipot, the more potentially
lethal the test. Hipot operators work in an environment
that calls for extreme caution. The severity of an electrical shock is dependent on a number of factors,
including voltage, current, frequency, duration of
exposure, current path, and the physical condition of the
person who receives the shock. For this reason we
recommend that manufacturers not use a 500 VA tester
unless the specifications they are testing to require it or
they are certain that the device they are testing is so
highly capacitive that a typical lower VA rated Hipot will
not be able to test the product.
The Hipot tests that manufacturers are required to
perform under the CE directives for safety testing are
largely based on the IEC (International Electrotechnical
Commission) and EN (European Norms) standards.
Some of these reference specifications mandate the use
of a Hipot tester with as much as 500 volt amperes (VA)
of output power (See Figure 10).
A Hipot’s VA rating is a measure of its output power,
calculated by multiplying the maximum voltage of the
Hipot by its maximum current output.
V = voltage
I = current
VA = volt amperes
VxI = VA
DC Voltage-Withstand Testing Advantages
DC Withstand testing is sometimes chosen as an alternative to the AC Withstand test because of some of the
advantages it offers. If the DUT is highly capacitive it
would require an AC Hipot which has a very high output
current capacity due to the capacitive reactance of the
product. This higher current capacity can expose the
operator to considerable safety risk. A DC tester can be
used which has a much lower current capacity to perform
the same test with much less risk to the operator.
Two important specifications that call for a 500 VA of
output power, without exception, are IEC 204 and EN
60204, part of the Machinery Directive, which became
effective on January 1, 1995. Any electrical machine
imported into Europe
requirements before it is
allowed to display the CE
mark. For many manufacturers, this means having
to test products with a
Hipot of a much higher
output rating than they
have previously used to
comply with U.S. safety-agency requirements. While
other specifications from UL and CSA (Canadian
Standards Association) also specify a 500 VA rating,
unlike the IEC and EN specs, they permit certain
During DC Hipot testing the item under test is charged.
The same test item capacitance that causes reactive
current in AC testing results in initial charging current
which exponentially drops to zero during DC testing.
Once the item under test is fully charged the only current
which is flowing is the true leakage current. This allows
a DC Hipot tester to clearly display only the true leakage
of the product under test. The other advantage to DC
testing is that since the charging current only
needs to be applied momentarily the output power
requirements of the DC Hipot tester can typically be
much less than what would be required in an AC tester to
test the same product.
A Hipot with 500 VA should provide enough output
power to test a device under a loaded condition without
allowing the output voltage to fall below the specified
By gradually applying the voltage and allowing the
charging current to diminish after each small increase,
highly capacitive products may be tested with far less
power than would be required by AC instruments. While
this reduces the inherent danger to the operator, it significantly increases the required testing time.
• Some models are AC/DC switchable, while others are
available with current displays. Current metering is
somewhat more popular in DC testing than in AC
because of the ability to monitor the decay of the
charging current.
In addition, DC Hipot testing is the only option for
testing some types of components, such as the voltage
ratings of capacitors and the inverse voltage ratings
of diodes.
The connections for the DC tests generally are the
same as for AC tests because the same insulation is being
stressed. The most important difference is that the
voltage must be applied gradually so that the charging
current will not exceed the leakage threshold.
DC Voltage Withstand Testing Disadvantages
Unless items being tested have virtually no capacitance, the test operator must gradually raise the voltage
from zero to the full test voltage. The more capacitive the
DUT, the slower the voltage must be raised.
When testing items with little capacitance, the DC test
can be similar to the AC test in that the gradual application of voltage is not as important.
Indications of Electrical Breakdown
Breakdown indications are the same in DC testing as in
AC testing (See Page 24), the DC withstand voltage of
the DUT will typically be higher than the AC withstand
voltage due to the peak value of the AC voltage is 1.414
times higher. The equivalent DC level would therefore
have to be at a minimum of 1.414 times the AC voltage.
Caution must still be taken when performing a DC test, if
the item under test does breakdown this does not mean
that the item was fully discharged, care must be taken to
discharge the DUT before handling.
This is very important when instruments with failure
and high-voltage shut-off circuitry are used, as they
almost instantaneously indicate failure if the total current
(including charging current) reaches the leakage
threshold. This requirement adds an undetermined
amount of time to the test and often calls for either
automatic instruments or more skilled operators.
The DUT must be discharged after the test. A good rule
of thumb is to apply a ground for the same length of time
as the high voltage was applied. Some instruments have
built-in discharge circuitry. When using such models,
leave the DUT connected for a sufficient time after the
test. DC only stresses the insulation in one polarity.
Regulatory agencies do not always accept DC testing
as a substitute for a required AC test. Even when they do,
the conversion factor by which the AC voltage must be
multiplied is not consistent—it can vary from 1.414 to
1.5 or 1.7.
Indications of Excessive Leakage Current
The total current drawn by the DUT is shown on the
current display or sensed by the failure circuit. It consists
of the leakage current, which is dependent on the present
voltage level, and the charging current, which is
dependent on the rate and amount of the last voltage
increase and the time that has elapsed since it occurred.
The current always increases during a voltage increase.
Although an AC Hipot test sometimes can be used in
place of a Line Voltage Leakage test, a DC Hipot test can
never substitute for a Line Voltage Leakage test. This is
because most products being tested will actually operate
on AC voltage.
When using instruments with a failure detector, it is
necessary to limit the rate at which the voltage is applied
to the DUT. If applied too fast, the failure detector may
shut down the Hipot indicating a failure, which is
actually a result of operator error.
Techniques of DC Voltage-Withstand Testing
Several varieties of DC voltage-withstand instruments
are available:
The test should be repeated, applying the voltage at a
slower rate of rise to be certain that the failures are from
excessive leakage or breakdown, and not due to charging
current. When using models with separate breakdown
and leakage indicators and no failure circuitry, expect
the leakage light to stay on for some time after a
voltage increase.
• Some are instruments with simple high-reactance
transformers with rectifiers and filters added to them.
• Some instruments use conventional transformers and
have failure and high-voltage shut-off circuits.
If the light stays on indefinitely or longer than
(Figure 11) Circuit for line leakage testing
ammeter is connected between any exposed metal part
and the neutral conductor, the ammeter must show less
than a specific current level.
expected, suspect excessive leakage.
On models with current metering, set the current range
switch to the highest range, and observe the current
meter after the full test voltage has been reached. Each
time the reading falls below the full scale value for each
lower range, change the range to the next step down.
Eventually, the reading should stabilize and can be
compared to the normal reading for the type of product
being tested. Of course, if the test operator wants to
monitor how the current increases with the voltage, the
test operator will have to record a meter reading after
each incremental voltage increase.
To simulate the effects of current on a human body, the
ammeter should have an input impedance of 1500 ohms
of resistance shunted by 0.15 µF of capacitance. This
electrical network is referred to as a measuring device.
The Measuring Device (MD) is a model of the human
body’s impedance. The recommended circuit to simulate
this impedance as specified by UL 544 for medical and
dental equipment is shown in figure 11. The measuring
device circuit differs depending upon the specification.
On instruments with manually set current ranges,
remember to select the highest current range each time
the voltage is about to be raised. This is because each
time you raise the voltage level you will also get an initial
inrush of additional current which could overextend your
metered range and possibly damage your meter.
In many products the required maximum current is 0.5
mA (2). Although there are products where current
leakage may exceed 0.5 mA—but not 0.75 mA—these
products must be equipped with a three-prong grounding
plug and appropriate user warnings. In most cases,
products intended for fixed mounting where they are
grounded in their installation are also allowed to exceed
0.5 mA. Leakage tests are first conducted with normal
line and neutral connections to the DUT, then with the
connections reversed. UL provides a schematic of a
recommended circuit for making this measurement
(See Figure 11).
More recent automatic instruments come complete
with a single display that monitors both voltage and
current as well as other information (See Figure 6).
Line Leakage Tests
Various studies show that the human body’s threshold
for perceiving electric current is approximately 1 mA
(1). Because body weights differ, some people feel
current at different levels. Once current exceeds a
person’s threshold it can cause a “startle reaction,”
which is an uncontrolled muscular spasm induced by a
sudden, unexpected electrical shock.
Although numerous product safety tests are normally
specified for electrical products, one of the most
confusing aspects of such electrical safety compliance
testing is leakage measurement. The two most important
and common instruments used to detect abnormal
leakage currents are the Line Leakage test and the Hipot
or Dielectric Withstand test. Line Leakage test is a
general term that actually describes three different types
of tests. Two of these tests are the Earth Leakage test
and the Enclosure Leakage test. The third test is the
Applied Part Leakage test which is required only for
medical equipment. All of these tests are used to
determine if products can be safely operated or handled
Because of the potential hazards these low-level
currents present to the human body, UL, CSA, VDE,
IEC and other private and governmental testing agencies
have set standards for the maximum amount of current
that may leak from a non-defective product operating at
its normal line voltage. If the product is energized and an
The leakage current measurement device in the Line
Leakage tester provides specific load requirements
which simulate both contact resistance and the resistance
of the human body. There are specific limits as to the
maximum allowable leakage currents that are acceptable
during a Line Leakage test. These limits vary depending
on the type of product being tested. Medical products
have a much lower limit especially for patient-applied
parts, because patients who are ill, unconscious, or
anaesthetized may not be able to detect potential hazards,
or their ability to react to them may be limited. For
instance, their skin may be penetrated or treated to obtain
a low skin resistance, which could pose a greater danger
to them.
without posing a shock hazard to the user.
(1) Mazer, William M., Electrical Accident
Investigation Handbook, Electrodata, Inc.,
Glen Echo, Md., 8/82 sec.
(2) Standard for Electric Air Heaters, UL 1025,
Underwriters Laboratories, Inc., Northbrook, Ill.,
4/84 sec. 29
Performing a Line Leakage Test
Many product safety specifications call for a Line
Leakage test to be performed either as a design (type) test
or as a production line test. Testing during the design
stage gives the engineer crucial information on the
integrity of the design, therefore an awareness of the
applicable safety standards with which a product must
comply is essential. Associated Research Line Leakage
testers are designed to meet the safety agency
compliance specifications as outlined by UL 544, UL
2601, UL 1563, UL 3101, IEC 1010, IEC 601-1 and the
European Norm (EN) specifications.
The Earth Leakage test must be carried out in both
normal line conditions and single fault conditions, such
as open neutral, reversed line and grounded functional
earth. If applicable, an Applied Part Leakage test must
also be performed. There are a minimum of eight
possible combinations for each type of test, and additional tests are specified for applied parts. Leakage
current limits can range from 0.01 milliamps to 10
milliamps depending on the type of DUT and the test that
is being performed. The primary difference between the
various Line Leakage tests is where the measuring device
is placed. The Enclosure Leakage test measures the
leakage current from the enclosure to other parts of the
enclosure that, in normal use excluding applied parts,
might be accessible to an operator or patient. The
Applied Part Leakage test measures the leakage current
from the patient lead connections back to the neutral
conductor and between patient leads, depending upon the
type of equipment.
The test is performed while the device under test
(DUT) is operating either at its nominal line voltage or a
110 percent of its nominal specified input voltage, under
both normal and single fault conditions. During the Earth
Leakage test, measurements are made from the ground
lead of the DUT to determine how much current flows
As new editions of many safety standards are
becoming harmonized with the “EN” specifications, the
leakage measurements tests are now following the
guidelines of the IEC 60950 standard. This standard
titled “Methods of Measurement of Touch Current and
Protective Conductor Current” utilizes different
measuring devices and may specify the measurements to
be done measuring either true RMS or Peak currents as a
peak measurement is more accurate for non-sinusoidal
(Figure 12) LINECHEK® Model 510L Automated
Line Leakage Tester.
back to the system neutral. During the Enclosure
Leakage test, current can be measured between various
points of the DUT chassis and system neutral (See Figure
11). The measurements, which are taken with a
measuring device specified by the safety agency to
simulate the impedance of the human body, indicate how
much leakage current an end user could be exposed to
under both normal and single fault conditions when the
DUT is operating.
Correlations Between Hipot Leakage & Line Leakage
The current measured during the Line Leakage test can
be used to calculate the approximate current trip setting
that should be used for a Hipot test. This would be an
approximate setting, since a DUT’s component
tolerances could cause slightly different leakage readings
among different DUT’s. In calculating correlating
The Line Leakage tester (See Figure 12) is designed to
automate line leakage testing in a production line or
laboratory environment.
Line Leakage Test Requirements
DUT chassis.
The Hipot test measures leakage from both currentcarrying components simultaneously, therefore it
displays a higher leakage reading. A good rule of thumb
is to set the Hipot trip current about 20 to 25 percent
higher than the value determined by the following calculation: (Hipot test voltage ÷ Line Leakage test voltage) x
Line Leakage test current = approximate Hipot current.
For example, take a Line Leakage test voltage of 240
volts, a Hipot test voltage of 1480 volts, and an actual
Line Leakage measurement of 2.0 milliamps. This calculation would look as follows: (1480 volts ÷ 240 volts) x
2.0 milliamps = 12.33 milliamps. Based on this calculation, and adding approximately 25 percent for
tolerance, the Hipot leakage setting could be set to about
15 milliamps.
(Figure 13A)
Insulation Resistance Measurements
Using an Insulation Resistance (IR) tester, connect
two points that are separated by insulation and take a
measurement. The measured value represents the
equivalent resistance of all the insulation that exists
between the two points and any component resistance
that might also be connected between the two points.
(Figure 13B)
The Insulation Resistance testers’ power supply
voltages vary from as low as 50 volts to as high as
10,000 volts, but the most common test voltages are 500
and 1,000 volts. All IR testers are supplied with DC
output voltage.
(Figure 13C)
When an Insulation Resistance test is made, there are
three components of current flow:
• Dielectric Absorption Current—The insulation
between two connection points may be thought of as a
dielectric and capable of forming a capacitance. A
phenomenon known as Dielectric Absorption occurs, in
which the dielectric “soaks up” current and releases it
when the potential is removed. This absorption occurs at
the same time that the current is charging and
discharging the capacitance, though it happens much
more slowly. It is affected by the type of dielectric and is
referred to as Dielectric Absorption Current, or IA (See
Figure 13A). Dielectric Absorption is particularly
important in capacitors and motors.
(Figure 13D)
To demonstrate this phenomenon, take a large
capacitor and charge it to its rated voltage, then allow it
to remain at that voltage for some length of time.
leakage settings, it is important to consider the fundamental differences between the way the Hipot and Line
Leakage tests are performed. Even though most Line
Leakage testers offer switching to test both sides of the
(hot and neutral) input line, they only measure leakage
from one current-carrying component at a time to the
Next, quickly and completely discharge the capacitor
by shorting the terminals until a voltmeter placed across
Hipot test. The IR test gives you an insulation value
usually in Megohms. Typically the higher the insulation
value, the better the condition of the insulation. IR
tests are sometimes specified as an additional test to
make sure the insulation was not damaged during the
Hipot test.
it reads zero.
Remove the voltmeter, and again allow the capacitor to
sit for some length of time with an open circuit across
its leads.
If you place the voltmeter across the capacitor again,
any voltage you find will be the result of Dielectric
Absorption. Some capacitors exhibit this phenomenon
more than others, with larger capacitors showing a more
pronounced effect.
Motor Testing
Those who manufacture, install, use and repair motors
find Insulation Resistance testing very useful in determining the quality of the insulation in a motor. To an
experienced individual who knows how to interpret
readings, a single insulation resistance measurement can
indicate whether a motor is fit for use.
• Charging Current—The current required to charge
a given capacitance is known as the Charging Current, or
IC (See Figure 13B). Like the Dielectric Absorption
Current, the Charging Current decays exponentially to
zero, but at a faster rate.
Information of real value is obtained when a measurement is made when a motor is new, and again at least
every year while it is in service.
In most cases, the Charging Current determines how
long it will take to make an accurate Insulation
Resistance measurement. Once the reading appears to
stabilize, the Charging Current will have decayed to
a point where it is negligible with respect to the
Leakage Current.
To test a motor with no history, a calculation called the
Polarization Index is sometimes applied. This index is
obtained by dividing a 10-minute Insulation Resistance
reading by a one-minute Insulation Resistance reading.
• Leakage Current—The current which flows through
the insulation is the Leakage Current, or IL (See Figure
13C). The voltage across the insulation divided by the
Leakage Current passing through it equals the Insulation
Resistance. To accurately measure insulation resistance,
wait until the Dielectric Absorption Current and the
Charging Current have decayed to the point where they
truly are negligible with respect to the Leakage Current.
For large motors, the Polarization Index should be at
least 2.
Some instruments with microprocessor control allow
the user to program a consistent delay time into the
instrument. This provides consistent results since the
exact amount of delay time is allowed for each test.
(Figure 14) The Hypot®III Model 3670 with
built-in IR Test capability.
The Total Current which flows is the sum of all three
components explained above, and is designated as IT
(See Figure 13D). Total Current (IT) decays exponentially from an initial maximum and approaches a
constant value. This constant represents the Leakage
Current. The Insulation Resistance reading is dependent
on the voltage across the insulation and the total current.
It increases exponentially from an initial minimum and
approaches a constant value—the actual insulation
resistance. Note that the reading will be smaller (and can
never be greater) than the actual resistance, due to the
effects of residual Dielectric Absorption Current and
Charging Current.
Component Testing
Another application for Insulation Resistance tests is
testing components before they are installed in a product.
Wire and cable, connectors, switches, transformers,
resistors, capacitors, printed circuit boards and other
components are specified to have a certain minimum
insulation resistance, and it is sometimes necessary to
verify that these components meet their specifications.
Why Measure Insulation Resistance?
The Insulation Resistance test is very similar to the
Pay attention to these restrictions to avoid damaging
the component or making improper comparisons.
Any component might have a limitation on the voltage
that might be applied to it, or the insulation resistance
might be specified to a particular voltage.
The grounding of electrical circuits and electrical
equipment is required to protect against electrical shock,
safeguard against fire, and to protect against damage to
electrical equipment. The grounding of the metal
enclosures or exposed dead metal on the equipment also
establishes a common ground or earthing reference or
zero potential difference between multiple pieces of
equipment which may be in the same proximity.
Use caution when selecting the proper test voltage. Do
not exceed the voltage rating of a component or of a
motor across the points where the measurement is to be
made. Many users prefer to use the highest voltage that
is available without exceeding the product’s rating.
In other cases, the customary test voltage is 500V
whether or not the product being tested has a
higher rating. Because an IR test can be a useful tool
for diagnostics and component checking, an IR test
mode is often included in some combination instruments
(See Figure 14).
A ground continuity test is normally required as a
production line test on electrical equipment to verify that
there is continuity in the ground circuit of the device. The
main function of this ground is to protect the operator of
the equipment against electrical shock. When an insulation fault develops between the line circuit and the
exposed metal parts, the ground conductor provides a
path for the dangerous fault currents to return to the
system ground at the supply source of the current. If the
ground circuit is of a low enough impedance, the current
will flow through the ground conductor of the equipment
allowing the excess current to flow, enabling circuit
breakers or fuses to open. By grounding the exposed
metal parts, all normal leakage current is safely routed to
ground and does not flow through people who touch the
Although the IR test can be a predictor of insulation
condition it does not replace the need to perform a
Dielectric Withstand test. The following are some types
of failures which are only detectable with a Hipot test:
Weak Insulating Materials, Pinholes in Insulation,
Inadequate Spacing of Components and Pinched
Polarization & Ground Continuity Tests
Polarization tests and Ground-Continuity tests often
are required to be performed with the Line Voltage
Leakage tests or the Dielectric Voltage-Withstand test.
Unlike other tests discussed thus far, these are not insulation tests. Instead, their purpose is to ensure that safety
connections have been made properly.
Of course, this system only works if the user does not
defeat the safety ground. Users often defeat safety
grounds by removing the ground prong from a plug or by
using an ungrounded three-to-two prong adapter.
Because these practices are so common, products with
three-wire line cords are still required to pass the same
Dielectric Voltage-Withstand tests as ungrounded
Cordset manufacturers and makers of products which
use polarized line or mains cords are required to conduct
Polarization tests. In some cases, this involves a
continuity test, while in others visually inspecting the
wiring is sufficient for compliance. The Polarization test
is designed to verify that the line and neutral conductors
are not interchanged and is often required as a
production line test.
Class I products utilize only basic insulation, the
integrity of the ground circuit is what protects the
(Figure 15) Circuit for Ground Bond Test
When utilizing an instrument that has an adjustable trip
point, the resistance of the test leads should be added to
the maximum resistance level allowed. For example, if
the maximum allowed ground bond resistance is 100
milliohms and the test lead resistance is 37 milliohms,
the trip should be set for 137 milliohms.
operator if a fault should occur in the insulation.
Ground Bond Tests
The Ground Bond test or Ground Impedance test
determines whether the safety ground circuit of the DUT
can adequately handle the fault current in case the
product’s insulation should ever become defective.
Should a product fail, a low impedance ground system is
essential to ensure that a circuit breaker or fuse on the
input line will act quickly enough to protect the user
from receiving a dangerous electrical shock.
• To use the electronic offset capability available on some
instruments, first connect the test connections together
at the contact point of the DUT. Then, set up the
instrument to perform a test and calibrate itself to automatically subtract this resistance level from future
Some international compliance safety agencies such as
CSA, IEC, VDE, BABT and TÜV require a Ground
Bond test on all DUT's as they leave the production line.
This test should not be confused with simple lowcurrent continuity tests. A low-current test indicates that
there is a safety ground connection, but it does not
completely test the integrity of that connection—for
example, it may not detect a ground connection that is
maintained by only a few strands of wire.
• The “Kelvin Method” could also be used to monitor the
induced voltage through a very low resistance
connection. This proven connection technique uses a
four-probe system to eliminate the resistance of any test
lead wire from the results. One set of leads applies the
required current for the test while a second, separate set
of leads measures the voltage drop across the DUT
directly at the contact. The Ground Bond test usually is
To test for a good bond of the DUT's ground system in
a production environment, an instrument must be able to
provide the required low voltage output current through
the DUT’s safety ground. At the same time, the
instrument must measure the induced voltage across the
safety ground circuit to determine the impedance of the
ground connection (See Figure 15).
Because the measured values are usually so low, the
user should be careful not to read the resistance of the
test leads that are used to connect the test instrument to
the DUT. If this is inadvertently done, it might be erroneously concluded that the DUT has a safety ground
failure, simply because the combined resistance of the
DUT and the test leads will have exceeded the maximum
resistance level.
(Figure 16) HYAMP®III Model 3140 shown
with a Hypot®III Model 3670.
performed before the Dielectric Voltage-Withstand test.
Make sure to use a test instrument that can eliminate
the test leads’ resistance from the test results.
Because a Hipot test is a stress test between the DUT’s
current-carrying and non-current carrying components,
you should first test the non-current carrying component
with a Ground Bond test to verify the non-current
carrying connection will hold its integrity if the current
carrying connection fails.
There are several techniques to account for test lead
• The first would be to simply perform a test with the
leads directly connected to each other without the DUT
For Ground Bond tests, choose compatible safety
instruments (See Figure 16) or a single instrument with
both Hipot and Ground Bond capability. That way, a
single connection to the DUT can be used to perform
Note the reading during this test and subtract this value
from your total reading once you test the actual DUT.
Functional Run Tests
While product-safety tests help ensure that a product is
safe, they do not provide any indication that the product
will operate correctly. A good example of this is a
product with a short circuit across the hot and neutral
conductors. This equipment will pass a Hipot test
because the hot and neutral normally are connected
together for that test. However, when the DUT is
connected to line power, the short circuit condition will
cause input circuit breakers or fuses to trip. To detect
failure conditions before a product is shipped, most
manufacturers run functional tests after final safety
testing to verify the functionality of the products (See
Figure 17). These tests verify that the product performs
high current and causes a failure on a weak connection.
Ground Continuity only verifies that the safety ground
connection exists. Since it is a low current test, it does
not use a specific measuring device, nor does it switch
input power configurations to the DUT into fault
conditions. The test simply determines leakage to the
case if the safety ground circuit is broken. In addition to
these tests, manufacturers may record power and power
factor measurements while the DUT is operating.
The Case for Automatic Testing
Depending upon the complexity of the DUT, the same
operator who performs product safety tests may perform
the run test at the end of the assembly operation. After a
product has passed safety tests, it is connected to line
power and the functional run tests are performed.
Usually, the operator has a limited amount of time to
perform both the safety and the run tests and do a visual
inspection. With a high-speed production line and many
opportunities for distractions, it is possible to miss a
problem in the product. Also, manually recording too
much information often results in lost productivity. All
this makes the consistency of tests that are performed
manually very questionable in most manufacturing environments. Many European Norm (EN) product safety
standards now require that manufacturers of consumer
products document all test results. Documentation also is
(Figure 17) RUNCHEK® Model 905D
Fully-Automated Run Test System.
its intended functions. The tests also may monitor the
input voltage and current of the DUT to detect any
problems. These parameters are not measured as part of
the safety testing, and the limits are product specific.
Tests While the DUT Is Operating
Current draw is the most common test performed while
running the DUT. This measures the current into the
DUT to determine that it is operating within its fuse
rating. Leakage Current, another common test, is a
simple measurement of leakage from the case of the
DUT to ground. This should not be confused with Line
Leakage. This simple leakage resistance must not exceed
0.1 W plus the resistance of the supply cord. An adequate
ground must have an impedance level low enough to
limit the voltage to ground and facilitate the operation of
the circuit protection device should a fault occur. Ground
Continuity normally is specified as a routine productionline test and can be done with a simple device such as a
test-light/battery-buzzer combination or ohmmeter,
although a more sophisticated test with some type of
consistent measurement parameter is recommended.
This test verifies that continuity of the ground conductor
is present. Ground Bond is the preferred method of
testing safety ground circuits on products sold in Europe
and in any other application where a good ground system
is critical. This test stresses the ground connection with
(Figure 18) OMNIA® Series 5 Electrical Safety and
Functional Run Testing in a single enclosure.
required of ISO compliant manufacturers.
Same Station Safety and Functional Run Testing
Today it is possible to offer one test station that
performs both safety and run tests with one connection to
the DUT. This can save a tremendous amount of time. An
automated system can monitor minimum and maximum
readings for Voltage, Current, Watts, Power Factor, and
Leakage Current (See Figure 18). The duration of the
tests also may be programmed into the system, providing
for more consistent tests. If any parameter falls outside
its limits, the system will signal a failure automatically.
Tests can be linked together to allow the operator to test
products that have multiple settings. All test data can be
stored to a file; all possible pass/fail statistics can be
recorded with the operator ID, date, and time. This
information can be viewed in detailed, summary, graphic
or stored in an ASCII format. It can be exported to a
spreadsheet, word-processing, or database program.
Automation also makes a change-over on the line much
faster because test programs for each type of product can
be loaded from a database. For manufacturers using bar
codes to identify products, test programs can be loaded
from a computer file linked to the bar code.
By automating the functional run test and the product
safety tests into the same test area and linking them
together, you can improve the reliability and efficiency
of production testing. The operator is less likely to skip a
test while trying to keep up with the production line and
does not have to read several meters during the testing
process since automatic instruments monitor violations
of preset limits. Each model and serial number can be
recorded along with the test results. As a result, the tests
are consistent from one product to the next, and data can
provide your engineering and quality departments with
valuable information.
Scanning Matrix Systems
Products such as transformers, motors, cables or any
DUT’s that require high voltage tests at various points
are ideal applications for use of scanning matrix
systems. Major concerns with manual multi-point
testing have been the high risk of incorrect connections
tional test points stand-alone external scanners can be
selected with up to 16 outputs. Scanners can also be
linked together allowing for even more connection
The latest scanners can control Hipot, Ground Bond
and Continuity test outputs. The switching sequence is
controlled either through the host safety testing
instrument or in some cases the scanner might be
controlled directly by PC control. Modular scanners
offer the benefit of flexibility in that they can be
configured to match the needs of various applications
allowing customization to specific test environments
(See Figure 19).
(Figure 19) Modular Scanner Model SC6540 for
multi-point or multiple product testing.
In addition to multi-point testing scanners can also be
used in test environments where it is desirable to
connect multiple products at one time and cycle through
testing in a batch mode. In either application scanners
have proven to save time and enhance operator safety.
due to operator error as well as the safety risk of having
the operator exposed to high voltage while making
connections. A way to address this is by using scanning
matrix systems that are basically switching networks
that can automatically make connections by switching
the safety tester test outputs to various test point
connections of the DUT.
Figure 19 - Model SC6540 modular scanner can be
configured with up to 16 test points for testing either
high voltage, high current or basic continuity tests.
Scanners can be built-in to some safety testers and
can have 4 to 8 output ports. For DUT’s requiring addi-
Recent Technology Developments
actually less costly than the old systems it
replaces. Please take time to read through the
following new developments and consider the
benefits these features could offer in your
specific application.
(Figure 20) Load Variation vs. Hipot Output
Line and Load Regulation
Line connected instruments can be
affected by a few uncontrollable external
factors. A Hipot instrument transforms the
input voltage of 115 or 230V AC to an output
value of several thousand volts. This means
that the output voltages stability is directly
linked to the input voltage level.
Line voltage fluctuations are common
in manufacturing settings where several pieces
of machinery may be powered by a single
input line circuit or where power is unreliable.
Fluctuations in input voltage can cause drastic
changes in the output voltage.
(Figure 21) Load Variation vs. Hipot Output
For example, if the line voltage drops
below a certain level, the output voltage can
actually fall below agency requirements. On
the other hand, if line voltage increases, the
output voltage can exceed recommended
voltage levels and damage the DUT.
Consider a product that has an
operating voltage of 120 volts. Based on the
rule of thumb calculations mentioned earlier
(double the operating voltage and add 1000
volts), a compliance agency requires test
voltage to be 1240 volts. This means that after
adjustment, the Hipot would produce approximately 10.33 volts of output for each volt of
input to achieve the 1240 volt requirement. Now, assume
that the line voltage drops to 105V. The Hipot is still set
to produce 10.33V for each volt of input, so the output
voltage now drops to about 1085V.
As reviewed in the section “Agency Requirements” on
page (7), the actual agency requirements for Dielectric
Withstand testing are quite basic. Most Hipots offered
today can meet these fundamental requirements. For the
most part, it has not been new agency specifications that
have driven new technology developments in safety
testing instruments. The demand has occurred because of
concern about operator safety as well as ensuring that
manufacturers adequately test the safety of their
products. Developments in technology, particularly
within the last decade, have made features available that
were previously impossible. Associated Research has
made a commitment to incorporate any new technology
into our products that can enhance user safety and
simplify testing procedures. Often this new technology is
Therefore, any device being tested while the input
voltage is low, actually is being tested at 155V below the
required test voltage.
Figure 20 shows the effect that line voltage variation
can have on the output test voltage of a Hipot.
This is why Hipot testers are now available with regulation circuitry that maintains the desired output voltage
setting. Such regulation circuitry monitors the input
voltage and electronically adjusts to assure that the preset
voltage level is maintained.
the no load setup feature. With this capability all test
parameters are adjusted digitally through a menu driven
program without high-voltage activated. This technique
is much safer and more accurate than older methods. For
this reason all Associated Research instruments now
include no load setup capability.
Loading conditions also can greatly affect the output
voltage applied to the DUT. Many manufacturers have a
standard procedure for setting the Hipot voltage while
the DUT is connected. This ensures that the proper test
voltage will be reached when the Hipot tester is operating
under a loaded condition.
Breakdown vs. Arcing
Breakdown can be defined as a condition where
voltage discharges across or through the insulation and
causes excessive current flow. Traditionally, a Hipot
tester is designed to monitor and measure the current
flow generated by this type of catastrophic insulation
failure. A Hipot with its current trip point exceeded will
indicate failure and high voltage will immediately be
shut down.
Unfortunately, the set-up procedure becomes a little
more complicated in manufacturing environments where
different products come down the assembly line and into
the testing area. These different products could represent
differing loads while the test instrument was originally
set to a single specific load.
Preceding a dielectric breakdown, corona or high
impedance arcing may form around a conductor. In some
environments corona can be defined as a luminous
discharge caused by the ionization of the air. Corona is a
partial breakdown caused by a concentration of electrical
stresses at the edge of an electrode in an electrical field.
High impedance arcs and corona generate high
frequency pulses which ride on the low frequency wave.
These pulses may have a frequency ranging from less
than 30 kHz to more than 1 MHz, and may be very short
in duration. Many times these pulses are much less than
10 microseconds (See Figure 22). These short duration
pulses or spikes may not immediately result in a
Figure 21 shows how output voltage changes if the
load is changed from 120 kohm to 2 megohms. This
compliance issue underscores the importance of
providing Hipot instrumentation that can maintain
constant output voltage even when the load varies. In the
past, the only way to solve this problem was to use Hipot
instruments that could provide extremely high current
levels without collapsing under load. In some cases,
these instruments could have output current capabilities
in excess of 100 milliamps.
This approach might have solved one problem, but it
created another one. Instruments that produced these
high output currents posed an unnecessary safety risk to
the test operator.
A load-regulated instrument can electronically monitor
the loading effect on the Hipot and compensate for these
load variations to maintain the preset output voltage. This
approach does not require the Hipot to have excess
output current capability, so it ensures compliance with
agency requirements while not risking operator safety.
All Associated Research Hipot testers include line and
load regulation.
(Figure 22)
No Load Setup of Trip Current & Voltage Output
Setting up the test parameters with an older style Hipot
tester is where the operator is at maximum risk of injury.
The reason for this is that with older analog instruments
it is necessary to run high voltage in order to set the
voltage and current trip parameters. During this setup
period the user must make adjustments with high-voltage
activated. A major benefit of microprocessor control is
disruptive discharge causing the current to increase or the
output voltage to drop. IEC 60601-1 for medical electronic equipment states the following: “During the test,
no flashover or breakdown shall occur. Slight corona
discharges are ignored, provided that they cease when the
test voltage is temporarily dropped to a lower value,
which must be higher however, than the reference
voltage and provided that the discharges do not provoke
a drop in the test voltage.” Please keep in mind that
although an agency might allow a DUT with corona to
pass the Hipot test, this corona may be an indication of a
potential problem in the insulation system.
detection for diagnostic or research and development
purposes but on the production line it may actually be
best to not use arc detection.
Many appliances such as power tools and vacuum
cleaners have low level arcing conditions present as part
of their normal operation. In many cases safety agencies
acknowledge that low level arcing does exist and allows
it in manufacturing tests. Therefore arc detection circuits
used in this type of production environment could show
a failure condition when indeed the product is good. On
other types of products such as medical electronics, especially patient connected devices, low level arcing
conditions need to be detected for safety reasons. In these
applications arc detection can have real benefits.
Arc Detection
The geometry of an arc is not a constant. For example,
breakdown voltages may vary greatly between two
rounded surfaces or two sharp points which have the
same gap spacing. The impedance and distributed capacitance of the circuits between the point where the arc is
generated and the detector may also effect the di/dt (rate
of change of current versus time) of the current
waveform being monitored by the arc detector. The
amount of voltage, rate of rise, polarity, and the
waveform all effect the speed in which corona and arcing
conditions occur. Temperature, humidity, and atmospheric pressure all influence the voltage at which corona
begins as well as breakdown voltage levels.
Because of test condition variables and the lack of
safety agency standards in defining maximum limits for
arcing and leakage currents, AR has taken a flexible
approach in its instrument designs. On instruments that
contain the functions to set both the high trip limits for
leakage current and trip limits for arcing conditions, we
feel the customer
must have the
variable limits that
can be adjusted to
meet specific test
requirements. We
also provide the
customer with the
option to enable or
disable the arc
This may be done
independently of
the high current trip
(Figure 23) Arc Detector
circuit that Hipot
testers must have
testing. Arc detection when used properly and under the
correct conditions can provide valuable information on
product design and safety. However, the manufacturer
must first determine that arc detection is applicable to
their products to avoid failing products that are actually
electrically safe.
An Arc Detection system incorporates a high pass filter
circuit that only responds to high frequencies that are
greater than 10 kHz. These high frequency signals are
fed into a comparator and checked against the sensitivity
level adjustment that the user selected during setup. If
this level is exceeded an interrupt signal is fed into the
CPU, which shuts down the Hipot in 400 microseconds
(See Figure 23). While the leakage and overload
detection circuits are always active, some instruments
allow the user to shut off the arc detection circuit. We
have found that many manufacturers may use arc
Real Current
When performing Hipot tests, voltage is applied
between current carrying conductors and accessible
conductive surfaces to test the insulation of the product.
The physical design of a product is primarily the
controlling factor that determines the capacitive
reactance of a product. Today many products have higher
capacitive leakage currents because filter capacitors have
been added to the input circuits to enable them to comply
with EMC regulations. The resistive leakage current
within a product is primarily dependent on the type of
insulating material that was chosen for that product and
the applied voltage. The exact value of the resistive
leakage or Real Current is usually the determining factor
that dictates the quality of the insulation at a particular
voltage. Unfortunately, the Reactive Current is often
much greater than the Real Current. Unless the two
components are separated, a doubling or more of the
Real Current leakage can go undetected. It is therefore
important to be able to separate these two leakage
currents. Any increase in the Real Current leakage is an
indication that the quality of the insulation has deteriorated due to age or workmanship issues during the
manufacturing cycle.
(Figure 24) Resistive Current
(Figure 25) Capacitive Current
A graphic example of the Real Current issue can be
seen while looking at Figure 27. A combination of
resistive and capacitive currents are produced on the
(Figure 26) Resistive & Capacitive Current
The leakage current which is due to the insulation
resistance of the product is resistive, which is in phase
with the applied voltage (See Figure 24). One problem
which arises is the circuit which we are testing is also a
circuit for a capacitor, (defined as two conductors
separated by a dielectric material). The application of AC
test voltage to a capacitive item causes a Reactive
Current that is 90 degrees out of phase with the applied
voltage (See Figure 25). The leakage current that is read
by most AC Hipot testers is the Vector Sum or Total of
the Reactive Current, and the Resistive Leakage Current
or Real Current. The Real Current is due to the insulation
resistance of the product and the applied voltage (See
Figure 26). This is why in some applications it is
important to use a commercially available AC Hipot
tester with the capability to read Real Current.
(Figure 27) Vector Sum Relationship
The alternative to using an AC Hipot tester with Real
Current is to use a DC Hipot. The advantage of using DC
is once the capacitance of the item under test is charged
to the test potential the only leakage current remaining is
due to the insulation resistance of the product.
Unfortunately, DC Hipot tests are not always accepted by
safety agencies.
device under test (DUT) which will produce some level
of phase shift between the voltage and current sine
waves. The Total Current sine wave is no longer either in
phase or 90 degrees out of phase with the voltage
waveform. To determine the Real Current we need to
sample the signal of the instantaneous Voltage and
Current and calculate the Real or Average Power (Watts),
this includes information regarding the Real Current
phase angle. This information is fed into the CPU which
then divides the average power by the average voltage
and the result is the Real Current. The formula is as
follows, V I cos(I) / V= I cos(I) = Real Current.
Because of this, electronic ramping is much more
popular in DC testing.
Patented Ramp-HI
A disadvantage of DC testing is that sometimes the
time required to allow charging current to stabilize is
considered excessive in some high volume manufacturing environments. Associated Research offers a
patented Ramp-HI feature that solves this problem. This
allows customers to use a DC Hipot and still satisfy high
volume production needs. The Ramp-HI system can be
programmed to allow for a higher trip setting during the
ramp cycle allowing the DUT to be charged as rapidly as
possible without causing false failures. Once the Hipot
reaches the full test voltage the processor will then revert
back to monitoring the actual trip setting which could be
a much lower value. If the leakage current does not drop
below the high trip setting by the time the Hipot switches
to the dwell mode, a high limit failure is indicated.
In cases where distributed capacitance in a product is a
problem and AC Dielectric Withstand tests are mandated
by safety agency specifications you should be using an
instrument that has a Real Current feature. This way you
are assured that the Real Current will be known and thus
the real quality of the insulation within your product will
also be known. An instrument without a Real Current
circuit may produce erroneous information about the
quality of the insulation system. Without Real Current
you would have to either perform a DC Hipot test which
may not be allowed by the safety agency or you may
need to perform an Insulation Resistance test to
determine the true quality of the insulation system.
Real Current saves you both time and money by not
having to purchase additional equipment or perform
additional tests.
High and Low Current Sense
The Hipot test usually is not monitored in an
automated testing environment. This means that it is not
always possible to visually confirm that the DUT has
been connected properly. An improperly connected
Hipot or an open conductor in a test lead will not show
excess current flow or electrical breakdown—two
conditions that indicate a failed test. In this type of
situation, the instrument may in fact give a green light to
products that have not even been tested.
Electronic Ramping (Up and Down)
Because Hipot testing instantly applies high-voltage to
a DUT, it may cause electrical damage to components.
To solve this problem, it was necessary to not only
develop a system that monitors and indicates a failure
when excessive current is present, but also to develop
circuitry that monitors minimum current conditions. This
enables the user to set the Hipot in such a way that it can
determine whether current levels fall within parameters
the user has already defined. During the test, if the
current level falls between the minimum and maximum
allowable levels, the DUT is considered to have passed.
If the Hipot detects current falling below the minimum
during the test, it gives a failure signal. This signal tells
the operator that a failure condition was caused by the
current dropping below the required minimum level. This
usually means that there is an open circuit condition or a
test lead has fallen off the DUT.
Several new testing techniques have been developed to
eliminate this problem. One such technique that was
developed as a solution is the ramp up and down feature.
This feature ensures that the DUT’s are not compromised
from the application of high voltage by providing a timed
and gradual method to increase and or decrease output
test voltage. The ramp up and down technology effectively reduces the amount of damage occurring on DUT’s
sensitive to rapid changes in voltage.
Ramping is also very important when performing a DC
Hipot test. A common problem with DC testing is that if
high-voltage is applied instantly or raised too quickly, a
false failure could be indicated by the Hipot because of
the in-rush charging current the DUT will initially draw.
If voltage is gradually brought up, false trips can be
avoided since the current drops as the DUT charges.
This system works very effectively in AC Hipot testing
where a minimum leakage level current is almost always
measurable. Unfortunately, during DC testing the
minimum level of current is often below the range a
conventional low current measurement circuit can detect.
The reason for this is that when first applying the DC
high-voltage, a capacitive DUT will cause in-rush current
to flow. But after the DUT is fully charged and during the
dwell cycle, the actual leakage can be very low or zero.
With conventional High/Low current systems this would
cause a false low trip as soon as the current drawn by the
DUT dropped below the minimum limit setting.
begin the calibration program. When prompted, the technician then enters the meter reading from the standard
meter right from the front panel keypad of the
instrument. Once the power to the instrument is shut off,
the new calibration values are automatically written to
the non-volatile memory of the test instrument. This
provides a very simple, and more importantly, a safer
way of doing calibration on all Associated Research
Patented Charge-LO
Fortunately technology has been developed that
addresses this problem and offers the benefits of
High/Low detection to DC Hipot users. The Charge-LO
system is a high speed detection circuit that detects the
presence of the charging current pulse when voltage is
initially applied to the DUT. It can be assumed that if any
charging current is flowing at any time, the Hipot must
be connected to the DUT. If the circuit does not detect
even momentary charging current the DUT fails the
patented Charge-LO test. This new system allows DC
Hipot users to have the security of knowing that the
DUT is properly connected and that a Hipot test is
being performed.
Patented CAL-ALERT®
Many of AR’s new instruments include clock chips
therefore AR has been able to add a new built-in calibration alert feature. This feature automatically alerts the
user when the instrument is due for annual calibration.
The calibration alert will allow the instrument to give an
advanced alert that the calibration due date is
approaching. The alert date is like an alarm clock that
will warn you in advance of the actual calibration due
date. After a calibration is performed the alert date is
automatically set 11 months after the calibration date.
The CAL-ALERT system effectively eliminates the need
for manual tracking of calibration dates and unnecessary
paperwork. Both of these advantages work to increase
the likelihood of maintaining the instrument within the
required specifications and lessens the responsibility of
the operator.
Software Calibration
Most safety agencies such as UL require annual calibration of all electrical safety testing instruments.
Although Associated Research recommends that
instruments be returned to the factory annually for calibration and updates, we realize this is not possible in all
cases. Some customers prefer to use their own in-house
metrology department to maintain the calibration
accuracy of all instruments. This has posed a safety
problem for the technicians responsible for performing
this calibration. Since Hipots output high-voltage,
removing covers can be extremely hazardous. To further
complicate this, older instruments utilize internal potentiometers which require the technician to adjust pots,
with a screwdriver, that are often times located very near
components that are at high-voltage potential.
Patented SmartGFI®
Another new safety feature that will be added to new
Associated Research products is a protection circuit
called SmartGFI. You may be familiar with the term GFI
(Ground Fault Interrupter) circuits or GFCI (Ground
Fault Circuit Interrupters). These types of safety circuits
are mandated today by the National Electrical Code
(NEC) and other organizations to be used in “wet” environments and are most commonly found in bathrooms,
kitchens and basements. Many line cord manufacturers
are also adding a GFI circuit to their line cords that are
connected to products that are being used in potentially
hazardous environments such as power tools, pressure
sprayers and hair dryers to name just a few.
In order to provide our customers with as safe an
instrument as possible, we have adopted software calibration on all instruments. This eliminates the
requirement for the technician to remove any covers and
reduces the possibility of accidental contact with highvoltage. This new calibration method also eliminates the
need for potentiometers which are difficult to adjust and
can often times drift, causing inaccurate test results. With
software controlled calibration the technician merely
connects a standard meter and presses a single button to
AR in its continuous effort to provide the safest high
voltage testing instruments has designed a new circuit to
help prevent electrical shock in cases where an operator
may come into contact with the high voltage circuit. The
SmartGFI basically has a sensing circuit that will open
thus disabling high voltage when excessive leakage flows
from chassis to earth ground. The circuit is smart because
it doesn’t matter if the DUT is in a “floating” or in a
“grounded” (earthed) configuration. It automatically
senses the DUT’s configuration and will turn itself on or
off. Other GFI circuits some manufacturers use today in
their safety testers must be turned on and off manually by
the operator depending upon if they are testing a DUT
that is floating or grounded. In the case of manually set
GFI circuits it is far too easy to forget to properly set or
reset this feature. In the case of the SmartGFI it is truly a
safety feature because we have eliminated the operator
from the equation, SmartGFI is always present working
transparently in the background. It is important to note
that any GFI circuit just like the SmartGFI circuit will
function correctly only in the case where a DUT is
floating and the safety tester is using a floating return
operator on the action they need to perform before
continuing the test.
Patented VERI-CHEK®
Verification of failure detect circuitry of the electrical safety tester is required by safety agencies such
as CSA, UL, TÜV and others to validate that the
instrument is performing and functioning correctly. A
common request by inspectors during on-site follow
up visits is to have the manufacturer prove the functionality of the instrument. The VERI-CHEK allows a
user to easily and quickly validate the operation of the
instrument. The VERI-CHEK can be enacted each
time the instrument is powered up. The instrument
then begins to display a series of user-friendly
prompts, which prompt the user through the steps
required for verification. When the verification
process is completed detailed results are displayed
indicating whether the instrument passed the verification. Functions that can be verified include AC
Hipot, DC Hipot, Ground Continuity, Ground Bond
and Insulation Resistance.
Enhanced Graphic Liquid Crystal Display
An Enhanced Graphic LCD provides the user with
flexibility in viewing test results, test set up, data and
even various menu prompts that are not available in
other types of displays. The enhanced graphic LCD
increases the area for display of information. This
effectively provides the user with greater visibility and
presents the information in an easier more readable
format. The operator is now able to view test set up
and results without having to interpret and decipher
abbreviations. The graphic LCD also allows the user
to view detailed prompts from the screen allowing
prompt functions to guide the user through the correct
test process. The enhanced graphic LCD makes electrical safety testing easier, clearer, and more efficient.
These latest technological developments help manufacturers quickly perform electrical safety tests while
ensuring that the tests comply with agency specifications. Incorporating microprocessor technology, many
new and enhanced functions have been added to address
the traditional limitations of AC and DC testing found in
analog Hipot designs. Software control provides the
operator with a user friendly interface and eliminates
many of the possibilities for errors.
Prompt Screens
Many applications require certain steps and procedures
to be taken during the test cycle. Applications will call
for the DUT switches to be activated or test leads and
probes to be applied in a different manner or removed all
together. The prompt feature was designed to help avoid
operator error that may occur with the complication of
adding various steps to the test cycle. The instrument can
be programmed to display prompt messages as a part of
a test cycle serving as a reminder to the operator. When
a prompt is used as part of a test set up, the test will pause
and a prompt will appear on the screen before the next
step is initiated and remain on the screen until the test
button is pressed. During the pause the operatorconfigured message is displayed instructing the test
In review, the five primary electrical safety tests are:
• Dielectric Voltage-Withstand Tests
• Line Voltage Leakage Tests
• Insulation Resistance Tests
• Polarization and Ground Continuity Tests
• Ground Bond Tests
A safety test instrument may incorporate any or all of
these test modes in a single instrument.
Automated Testing
Every manufacturer is familiar with the inherent
conflict between the need to produce products quickly
and efficiently and the need to provide adequate testing.
that it can be retrieved and evaluated to meet these information and decision needs.
Another important reason for the growing need to
automate is to be ISO compliant. One of ISO’s main
objectives is to ensure that manufacturers can prove that
their products have been adequately tested and documented. If a manufacturer has automated records of the
test results required by a safety agency, he has the
necessary documentation to prove all products have
passed the tests.
This conflict of interest can tempt manufacturers to
take shortcuts that compromise the operator and product
safety. Fortunately, modern test instruments have finally
reached a level of sophistication that eliminates the need
to make this type of trade-off. Integrated and automated
test systems can perform all required tests on the DUT
quickly, accurately and through a single connection. As a
result, test operators no longer need to make multiple
connections, the tests themselves are more reliable, and
operators can perform tests far more quickly and at a
lower safety risk. Test operators and manufacturers also
need to store and retrieve test information. Automation
fulfills that need.
Furthermore, keeping the results from various safety
tests on file can shield the manufacturer from potential
litigation related to product safety.
Many U.S. manufacturers are successfully selling their
products in Europe, and many products shipped to
Associated Research offers our Autoware®
software to control our complete line of
automated test instruments. This stand-alone
software captures, stores and analyzes test
results (See Figure 28).
Many manufacturers collect and analyze
the data they gather from successive testing
and use it as information to make their
products safer and more reliable, as well as
to comply with ISO, TQM, SPC and some
IEC requirements.
For example, a manufacturer might
analyze current leakage readings during a
Hipot test. Data kept on file over several
years might indicate that typical leakage
readings during a 1500V test, on a certain
DUT, were consistently 2 milliamps. If this
manufacturer produced the same product
and later noticed readings as high as 5
milliamps, he might want to know why the
new test results varied from the old readings.
Neither of these conditions would cause a
failure if the leakage trip point on the Hipot
were set to 10 milliamps, but the increase in
leakage current suggests that something in
the manufacturer’s process may have
changed and should be reviewed.
A computer-controlled safety test system
can easily be configured to store test data so
(Figure 28) Fully-Automated Test Station with OMNIA® Series 6
set-up for PC control through Autoware® software.
Europe must display the CE mark to indicate compliance
with European Community standards.
IEEE (GPIB) Interface—The GPIB interface,
sometimes called the General Purpose Interface Bus, is a
general purpose digital interface system that can be used
to transfer data between two or more devices.
One requirement to obtain the CE mark stipulates that
manufacturers must conduct proper testing and keep
adequate records of test results. Using an automated
system controlled by a computer can quickly transform
data filing and storage into a relatively simple task.
Particularly well suited for interconnecting computers
and instruments, this interface requires the installation of
a GPIB interface card into a computer and is the most
popular choice in controlling instrumentation. The
GPIB interface can be a very economical choice since it
gives the test operator the ability to control up to 15
instruments on a single bus.
Three methods are commonly used to interface a
compliance safety instrument into an automatic
test system.
Programmable Logic Control (PLC)—Some electrical safety testing instruments come with proprietary
interfaces that provide the test operator with a convenient
way to connect the instrument to a variety of test
instruments. These interfaces range from a simple foot
switch for hands-free test initiation, to a computer-based
automatic test system for statistical process control and
ISO compliance.
Another advantage to GPIB is its high data transfer
rate of up to several Megabytes per second. Although bus
extender devices are available, the GPIB interface’s basic
limitation is that the bus length cannot exceed 20 meters
(65 feet) and the distance between devices cannot exceed
two meters (6.5 feet) (See Figure 28).
A computer interface allows the operator to access all
set-up modes of the safety instruments through a
computer. It allows the test operator to automatically and
quickly cycle through all the tests he or she is required to
perform and to store and evaluate all the test results.
The benefit of this type of automation is that it does not
necessarily require computer programming to set up a
basic test system. Through simple switches and analog
inputs and outputs, the instrument can control most
functions remotely.
Many manufacturers are concerned with the operator
skill level required to set up and use an automated
system. This concern has been addressed by some manufacturers of computer-controlled safety test instruments.
Automatic systems can be purchased with a software
package that guides the test operator through the set up
with a Windows-style program.
Using this type of proprietary interface to control test
functions and retrieve test data through a computer, you
may need a special controller card and interface cable.
You can also use instrument control software packages to
control many functions of safety test instruments through
a user interface on a computer. Another choice is to
consider a safety test instrument that comes complete
with industry standard interfaces that can easily be incorporated into an already complete automated test system.
While the best method for automating electrical safety
tests depends upon the preference and requirements of
the specific manufacturer, technology and instrumentation is available to assist you in thoroughly testing each
product. You can then ensure the electrical safety of your
operators and the safety of those who use your products.
RS-232 Interface—Another method of connecting the
instruments to computers is to use an RS-232 interface.
An advantage of this type of system is that most
computers come with an RS-232 port, no special
controller card is required, and there are fewer
constraints on the length of interface cable needed to
connect the test instruments to the computer. However,
there are two limitations: the RS-232 interface primarily
is used to connect a computer to a single test instrument;
and RS-232 is a serial communication method which is
much slower than other methods of interfacing, such
as GPIB.
Association of German
Electrical Engineers (VDE) ..7,15,20
Test ................................9,11,19,21,29
Leakage Test,
Line Voltage ..................6,14-17,19,29
High-Reactance Transformer ..12,14
120kohm Resistor..............................9
British Standards Institution
(BSI) ..................................................7
Hipot Test....3,8,11-14,16-21,23-28,30
Polarization Index ..........................18
Insulation Damage............................9
Polarization Test..............................19
Resistance ..............6,9,17,18,26,27,29
Ramp HI ..........................................27
International Electrotechnical
Routine Production Line Test ....8,21
Japanese Standards Association
Startle Reaction............................3,15
Leakage ............8,9,12-17,21,25-28,30
Underwriters Laboratories, Inc.
(UL) ............1,4,7-9,12,13,15,16,28,29
Canadian Standards Association
Charge LO ......................................28
Charging Current ......13,14,18,27,28
Design Test......................................7,8
Dielectric Absorption Current..17,18
Dielectric Voltage-Withstand
Test ............1,6,7,11,15,19,20,23,27,29
Double-Insulated Product ..........8,11
Ground Path ..................................1,3
Current ........12-16,18,19,21,25-27,30
Reactive Current ....................9,13,26
Safety Ground ........................1,19-21
Threshold of Perceptibility ............15
Ungrounded Appliance................1,19
(APPENDIX A) Glossary of Terms
CLASS II PRODUCTS—Products not grounded
through the input cord. These products must have double insulation.
ALTERNATING CURRENT (AC)—Current that reverses
direction on a regular basis (usually 60 times per second in the
United States).
CONDUCTIVE—Having a volume resistivity of no more than
103 ohm-cm or a surface resistivity of no more than 105 ohms per
square cm.
ARC DETECTION—The ability of a circuit to detect the short
duration current spikes normally in the range of 10 microseconds
which have peak amplitudes in the milliamp range. These high
frequency spikes normally appear on the peaks of the output wave
prior to catastrophic or destructive arc breakdown which result in
complete failure of the insulation.
CONDUCTOR—A solid or liquid material that current can pass
through, and has a volume resistivity of no more than 103 ohm-cm.
DIELECTRIC—An insulating material positioned between two
conductive materials in such a way that a charge or voltage can
appear across the two conductive materials.
BREAKDOWN—The failure of insulation to effectively prevent the
flow of current, sometimes evidenced by arcing. If voltage is
gradually raised, breakdown will begin at a certain voltage level
(whereby current flow is not directly proportional to voltage). Once
breakdown current flows, especially for a period of time, the next
gradual application of voltage will often show breakdown beginning
at a lower voltage than initially measured.
DIRECT CURRENT (DC)—Current that only flows in one
direction. Direct current comes from a polarized source, meaning
one terminal is always at a higher potential than
the other.
DOUBLE INSULATED PRODUCTS—This is a product where
the insulation is comprised of both Basic and Supplementary
Insulation. The basic insulation is the insulation which is applied to
live parts to provide basic protection against electrical shock.
Supplementary insulation is independent insulation applied in
addition to basic insulation in order to provide protection against
electrical shock in the event of a failure of basic insulation.
CAL-ALERT®—The patented CAL-ALERT feature automatically
alerts the user when the instrument is due for re-calibration. This
eliminates the need for manual tracking of calibration dates.
CE MARK—The CE Mark is the manufacturer’s or importer’s
mark of conformity declaring compliance with all applicable
directives (Safety, EMC, Machinery, Medical and others). The use of
the CE Marking and the Declaration of Conformity will be
mandatory for most products sold in the European Community.
DUT—Device Under Test.
CHARGE-LO—The Charge-LO Circuit sets a minimum charging
current which is based on the DC test voltage, the rate of rise, and
the capacitance of the DUT. This circuit confirms that the DUT is
connected when performing a test.
FREQUENCY—The number of complete cycles in one second of
alternating current, voltage, electromagnetic or sound pressure. In
the case of alternating current and other forms of wave motion it is
expressed in hertz.
CLASS I PRODUCTS—Products grounded through a third pin of
the input cord.
GPIB— General Purpose Interface Bus.
Glossary Continued
TEST—Common terms for the deliberate application of overvoltage to a DUT to test dielectric strength.
charging current during the Ramp function which is higher than the
high limit setting which would be chosen for the dwell cycle. This
allows you to charge the DUT as rapidly as possible without causing
false failures.
IEEE-488—A GPIB standard for instrument control.
RS-232—A standard form of serial communication through a
personal computer.
INSULATING—Having a volume resistivity of at least 1012 ohmcm or a surface resistivity of at least 1014 ohms per square cm.
SENSITIVITY—The minimum current flow required to cause an
indication of unacceptable performance during a Dielectric VoltageWithstand test.
INSULATION—Gas, liquid, or solid material that has a volume
resistivity of at least 1012 ohm-cm and is used to reduce or prevent
current flow between conductors.
SmartGFI®—The patented SmartGFI is a high speed shut down
circuit that provides maximum operator protection. If the circuit
detects excessive leakage to ground, it shuts down the high voltage
in less than 1 millisecond. SmartGFI is automatically activated if the
DUT is not grounded. The operator does not need to make the
decision whether to activate the SmartGFI.
ISO—International Standards Organization .
LEAKAGE—AC or DC current flow through insulation and over
its surfaces, and AC current flow through a capacitance (whereby
current flow is directly proportional to voltage). If breakdown
does not occur, the insulation and/or capacitance is considered a
constant impedance.
SPC—Statistical Process Control. A system by which one samples
and inspects the output of a process to determine if one should
adjust the process to bring the items or goods into an acceptable
quality standard.
MEGOHMMETER—A meter capable of measuring resistances
greater than 200 megohms. Usually requires a higher voltage power
supply than ohmmeters that measure less than 200 megohms.
VERI-CHEK®—The patented VERI-CHEK feature is a menu
driven process by which the instrument’s failure detectors are proven
to be functioning properly, “verifying” the functionality of the electrical safety tester and connected accessories.
PLC—Programmable Logic Control, an automation method using
relay technology.
RAMP-HI—The Ramp-HI feature allows you to set a high limit
(APPENDIX B) Associated Research Patents
U.S. Patent No.
This patent covers the VERI-CHEK® feature, an internal verification system, found in Associated Research
high-voltage safety testers to verify the functionality of the tester.
This patent covers the SmartGFI® circuit used in Associated Research high voltage safety testers to protect operators
from exposure to high voltage.
This patent covers the interconnection of a run test system to an electrical safety tester including the built-in high
voltage switching circuit.
This patent covers an advanced user interface including features such as Pause/Prompt, CAL-ALERT®, Security
Access Functions and a flexible menu structure allowing tests to be added through plug in modules.
This patent covers multi-function safety compliance analyzers that are capable of performing AC and DC Dielectric
tests as well as Insulation Resistance and either Ground Continuity or Ground Bond with a single instrument.
This patent covers the multiple circuits used in our line leakage testers to simulate the impedance of the human body.
This patent covers the exclusive RAMP-HI® circuit as used in DC Hipot testing to allow a higher level of current draw
during the ramping to allow for more rapid charging of the device under test.
This patent covers the exclusive CHARGE-LO® circuit as used in DC Hipot testing to detect charging current as an
indication that the device under test is properly connected.
This patent covers the H.V. auto discharge circuit that is used in all AR DC dielectric withstand testers.
Modular Scanning Matrix
OMNIA 8100 Series
Multi-Function Electrical Safety Compliance Analyzers
(APPENDIX C) Safety Agency Listings
The CB scheme is based on the IEC standard and means
that a recognized National Certification Body (NCB) has
tested our products and they are recognized in more then 30
The most recognized International Safety mark. This safety
listing signifies that the product was safety tested to IEC
CE is the abbreviation of the European Communities and this
mark tells customs officials in the European Union that the
product complies with one or more of the EC Directives.
This mark indicates compliance with both Canadian and U.S.
requirements. It signifies that the products have been tested to
UL 61010-1 and listed.
Associated Research in early 1998 began a program to safety list all of its products. We received the first coveted TÜV-GS certification on March 3, 1998. Since then the following instruments have been tested and certified by the safety agency shown below. In
addition, all these products have passed EN61010 for CE compliance. AR is the only company in its industry to carry the TÜV-GS
International Safety listing as well as the UL safety listing on some models.
CB Scheme
Certificate No.
Certificate No.
Listing No.
Stand-alone Line Leakage Tester
30A Ground Bond Tester
40A Ground Bond Tester
DE 02007384
60A Ground Bond Tester
DE 02005714
AC Withstand Voltage Tester
AC/DC Withstand Voltage Tester
AC/DC/IR Withstand Voltage Tester
Ground Bond Tester
AC Withstand Voltage Tester
AC/DC Withstand Voltage Tester
500 VA Safety Compliance Analyzer
500 VA Safety Compliance Analyzer
AC/DC/IR Safety Analyzer
AC Safety Compliance Analyzer
AC/DC/IR Safety Compliance Analyzer
OMNIA Electrical Safety Compliance Analyzer
approval pending
approval pending
approval pending
OMNIA Electrical Safety Compliance Analyzer
approval pending
approval pending
approval pending
OMNIA Electrical Safety Compliance Analyzer
approval pending
approval pending
approval pending
No Breakdown
Max. I
Test Time
25 A AC or DC
25 A AC or DC
Test Current
1.0-3.0 KVAC or
DC See Spec.
Test Voltage*
No Breakdown
Max. I
Test Time
≤ 0.1Ω
≤ 0.1Ω
≤ 12 V
≤ 12 V
≤ 0.1Ω
40 A for 20 A CKT ≤ 12 V
Continuity test
Max. R
V Limit
Test Current*
1.0/1.5 KVAC
115/230 V or
2121 VDC
Test Voltage*
Test Time
30 A 60 Hz
30 A 60 Hz
Test Current
No Breakdown
Max. I
10-25 A
10-25 A
Test Current
Test Time
≤ 0.1Ω
≤ 0.1Ω
Max. R
V Limit
3.5 mA
Max. I
Not Required
< 300
Test Time Test Voltage
2 min
3.5 mA
Max. I
Not Required
< 300
Test Time Test Voltage
Max. I
See Spec.
See Spec.
Test Time Test Voltage
≥ 2MΩ
Not Required
Test Time V Limit Max. R
≥ 2MΩ
Not Required
Test Time V Limit Max. R
≥ 2MΩ
Not Required
Test Time V Limit Max. R
Not Required
Not Required
Test Time V Limit Max. R
NUMBER: EN 60601-1 (IEC) 601 UL 2601-1
< 4 V 133 mΩ
< 4 V 133 mΩ
≤ 12 V
≤ 12 V
Max. R
V Limit
60s, 10s ramp
3.5 mA
Not Required
< 300
Max. I
NUMBER: CSA 22.2N950 (CSA 22.2 No. 0.4)
No Breakdown
Max. I
1.0-3.0 KVAC or
2121 VDC
Test Voltage*
Test Time Test Voltage
NUMBER: CAN/CSA 22.2 No. 60950-1-3 UL 60950-1
Max. R
V Limit
NUMBER: EN 60950 (IEC) 60950 (EN 50116)
1.0-3.0 KVAC or
DC see spec.
Test Voltage*
*If the DUT is fused, the Ground Bond test is 2x Fuse Rating of DUT. Max R should be < 2.5 V and test time should be 120s.
(APPENDIX D) Sample Safety Agency Specifications
Test Time
No Breakdown
Max. I
820-1350 VAC or
1159-1900 VDC
Test Voltage*
No Breakdown
Max. I
< 4 V 133 mΩ
< 4 V 133 mΩ
≤ 12 V
≤ 12 V
Max. R
V Limit
25 A
2s ramp
2s dwell
Test Time
Test Time
30 A 60 Hz
≤ 0.1Ω
≤ 10 V
3.5 mA
Max. I
Not Required
< 300
Test Time Test Voltage
< 4 V 133 mΩ
≤ 12 V
Basic continuity any device
Max. R
V Limit
2 min
3.5 mA
Max. I
Not Required
< 300
Test Time Test Voltage
≥ 2MΩ
Not Required
Not Required
Test Time V Limit Max. R
Not Required
Not Required
Not Required
Test Time V Limit Max. R
UL 61010-1
0.5 mA
Not Required
< 300
Max. I
Test Time Test Voltage
Test Time V Limit Max. R
Not Required
Not Required
Test Time V Limit Max. R
NUMBER: CSA C22.2 No. 1010.1 (CSA 22.2 No. 0.4)
Basic continuity any device
Max. R
V Limit
Test Current
3.5 mA
Not Required
< 300
Max. I
2 min
Test Time Test Voltage
NUMBER: EN 61010-1 IEC (1010)
Test Current
25 A
≤ 0.1Ω or ≤ 0.2Ω
See Spec.
Max. R
Basic continuity any device
≤ 6 VAC
V Limit
Test Current
820-1350 VAC or
1159-1900 VDC
Test Voltage*
30 A 60 Hz
30 A 60 Hz
Test Current
Test Time
No Breakdown
Max. I
1.0-3.0 KVAC
See Spec.
Test Voltage*
1.0 KVAC or
1.0 + 2X rated V
No Breakdown
Max. I
1.0/1.5 KVAC or
115/230 V or
2121 VDC
Test Voltage*
NUMBER: CSA 22.2 No. 601.1 (CSA 22.2 No. 0.4)
Sample Safety Agency Specifications Cont…
No Breakdown
Max. I
No Breakdown
Max. I
Test Voltage*
1.0 KVAC or
1.0 + 2X rated V
1.2 or 1.0 + 2X
rated V
No Breakdown
Max. I
No Breakdown
Max. I
1.0-3.0 KVAC
See Spec.
Test Voltage*
1.0-3.0 KVAC
See Spec.
Test Voltage*
1.0-3.5 KVAC
See Spec.
Test Voltage*
Test Current
Max. R
Basic continuity any device
Basic continuity any device
V Limit
Test Current
Max. R
Basic continuity any device
Not Required
V Limit
Test Current
Max. R
Basic continuity any device
Not Required
V Limit
Test Time
Test Current
Max. R
Basic continuity any device
Not Required
V Limit
Test Time
Test Time
60s 5s ramp
Test Time
Max. I
0.5-3.5 mA
See Spec.
Not Required
Max. I
≤0.5-0.75 mA
See Spec.
Not Required
< 300
Test Time Test Voltage
Not Required
Not Required
Max. I
Not Required
≥ 50 KΩ
Test Time V Limit Max. R
Not Required
Not Required
Test Time V Limit Max. R
Not Required
Test Time V Limit Max. R
Max. I
Test Time Test Voltage
Not Required
≥ 50 KΩ
Double Insulated Requires
≥ 1 MΩ
Test Time V Limit Max. R
≤ 0.5-0.75 mA
See Spec.
Not Required
< 300
Test Time Test Voltage
Not Required
< 300
Test Time Test Voltage
Sample Safety Agency Specifications Cont…
1.0 KVAC
No Breakdown
Max. I
1.2 KVAC 1.0 KVAC
No Breakdown
Max. I
Max. R
Basic continuity any device
Not Required
V Limit
Test Time
V Limit
Test Time
Max. R
Test Current
Max. R
Basic continuity any device
Not Required
V Limit
1s 60s
Test Time
Test Current
Max. R
Basic continuity any device
Not Required
V Limit
Max. I
0.5-2.5 mA
See Spec.
Max. I
0.5-5 mA
See Spec.
Max. I
0.5-2.5 mA
See Spec.
Not Required
< 300
Test Time Test Voltage
Not Required
< 300
Test Time Test Voltage
Not Required
≥ 50 KΩ
≥ 50 KΩ
Not Required
≥ 50 KΩ
Test Time V Limit Max. R
Not Required
Not Required
Test Time V Limit Max. R
Not Required
Test Time V Limit Max. R
Test Time V Limit Max. R
CSA C22.2 No. 343
Not Required
< 300
Test Time Test Voltage
NUMBER: UL 507 (2)
Basic continuity any device
≤ 0.75
Not Required
< 300
Max. I
Test Time Test Voltage
Basic continuity any device ≤ 0.1 Ω
Test Current
Test Voltage*
1.2-3.0 KVAC
See Spec.
Test Voltage*
Test Current
No Breakdown
Max. I
1.0 KVAC or
1.0 + 2X rated V
Test Voltage*
Test Time
No Breakdown
Max. I
600 V-1200 V
See AC Spec.
500 V or 1.0 KVAC +
2X rated V
Test Voltage*
1.0-2.5 KVAC
See Spec.
Sample Safety Agency Specifications Cont…
1.0-2.5 KVAC
1.2-2.5 KVAC
No Breakdown
Max. I
Test Current
Max. R
Basic continuity any device
Not Required
V Limit
Test Current
Max. R
Basic continuity any device
Not Required
V Limit
Test Time
Test Current
Max. R
Basic continuity any device
Not Required
V Limit
Test Time
Not Required
Max. I
Max. I
0.5-3.5 mA
See Spec.
Not Required
< 300
Test Time Test Voltage
Not Required
Not Required
Test Time Test Voltage
Not Required
≥ 50 KΩ
Not Required
≥ 250 KΩ
Test Time V Limit Max. R
Test Time V Limit Max. R
Not Required
Test Time V Limit Max. R
Max. I
0.5-2.5 mA
See Spec.
Not Required
< 300
Test Time Test Voltage
Exceptions and deviations exist in all specifications, even those that are “harmonized”. The examples shown above are representative samples of some of the most commonly used safety
standards. These are examples only and it is AR’s opinion that you should check your particular standard or check with your local compliance safety agency before setting up your testing
compliance programs. Significant differences may exist between “performance” or “type” tests and “production” or “routine” tests.
* Test Voltage is listed for products rated up to 250 VAC Primary to Earth and Primary to Case.
(1) Requires a 500 VA output Hipot tester for Performance and Production line tests.
(2) Excludes Recreational Vehicle Fans (see standard).
(3) There is no clear indication of either a Ground Bond test or Ground Continuity test being required. However, AR recommends that a Ground Bond test be performed
on a routine production line basis.
No Breakdown
Max. I
1s 60s
5s ramp 60s
Test Time
Test Voltage*
1.2 KVAC or
1.2 KVAC + 2.4
SPAS (1)
Test Voltage*
No Breakdown
Max. I
1.0 KVAC < 1/2 hp 1.0
KVAC + 2X rating > 1/2 hp
1.2 KVAC 1.0 KVAC
1.0 KVAC
Test Voltage*
Sample Safety Agency Specifications Cont…
(APPENDIX E) Sources of Additional Information
Associated Research, Inc. Web Site
This site includes full information on all our instruments, links to other safety related sites and technical articles to help answer the most common safety testing
application questions. If you do not have access to the Internet you can use the enclosed reply card to request a hard copies of all AR’s literature
International Product Safety News
E-mail: [email protected]
Japanese Standards Association
1-24, Akasaka 4, Minato-ku, Tokyo 107
Publisher of English translations of Japanese Industrial Standards.
American National Standards Institute
11 West 42nd Street, 13th Floor, New York, NY 10036
U.S. source for IEC standards and other domestic and
international standards.
Asociación de Normalización y Certificación, A.C. (ANCE)
Av. Lázaro Cárdenas No. 869 Fracc. 3, esq. con Júpiter
Col. Nueva Industrial Vallejo C.P. 07700, México, D.F.
Phone: +52 (55) 5747-4550 Fax: +52 (55) 5747-4560
E-mail: [email protected]
National Institute of Standards and Technology
Gaithersburg, MD 20899-0001
National Electric Manufacturers Association
Standards Publication Office
2101 L. Street, N.W., Suite 300, Washington, D.C. 20037
Phone: 202-457-8400 Fax: 202-457-8473
Issues standards for electrical products.
A free catalog is published annually.
100 Barr Harbor Drive, West Conshohocken, PA 19428-2959
Phone: 610-832-9585 Fax: 610-832-9555
E-mail: [email protected]
1 Station View, Guildford, Surrey, GU1 4JY
OSHA Region V Office
230 South Dearborn Street, Room 3244, Chicago, IL 60604
Phone: 312-353-2220
British Approvals Board for Telecommunications
Claremont House
34 Molesey Road, Hersham, Walton-on-Thames,
Surrey KT12 4RQ
The Standards Council of Canada
45 O’Conner Street, Suite 1200, Ottawa, K1P 6N7
Phone: 613-238-3222 or 1-800-267-8220 (Sales only)
Fax: 613-995-4564
E-mail: [email protected]
British Standards Institution
389 Chiswick High Road, London W4 4AL
TÜV Rheinland of North America, Inc.
12 Commerce Road, Newton, CT 06470
Phone: 203-426-0888
Canadian Standards Association
178 Rexdale Boulevard, Rexdale, Ontario, M9W 1R3
Comité Européen de Normalisation Electrotechnique
Rue de Stassart, 35, B-1050 Brussels M9W 1R3
Underwriters Laboratories, Inc.
Publications Stock 333 Pfingsten Road, Northbrook, Illinois 60062
A free catalog of Standards for Safety is published twice a year.
IEC Central Office
3, rue de Verenbé, P.O. Box 131, 1211 Geneva 20
U.S. Consumer Product Safety Commission
Washington, D.C. 20207
Phone: 800-638-2772
Phone: (Hearing/Speech Impaired) 800-638-8270
E-mail: [email protected]
ISO International Standards Organization
1, rue de Verenbé Case postale 56 CH-1211 Geneva 20
Institute of Electrical and Electronic Engineers, Inc.
345 East 47th Street, New York, NY 10017
Phone: 800-678-IEEE (Customer Service)
E-mail: [email protected]
VDE-Verband Deutscher Elektrotechniker
Merlinstrasse 28, D-63069 Offenbach
Publisher of VDE standards and English translations.
Or call us toll-free at:
13860 West Laurel Dr., Lake Forest, IL, U.S.A. 60045-4546
Tel: +1-847-367-4077 Fax: +1-847-367-4080
E-mail: [email protected]
+1-800-858-TEST (8378)
+1-800-858-TEST (8378)
Or call us toll-free at:
13860 West Laurel Dr., Lake Forest, IL, U.S.A. 60045-4546
Tel: +1-847-367-4077 Fax: +1-847-367-4080
E-mail: [email protected]
13860 W Laurel Dr
Lake Forest, IL 60045-9734
The Operator’s Guide to Electrical
Product Safety Testing
Please have a salesperson
contact me
Hypot III
3-6 months
Name (please print):
6-9 months
For filing purposes only
Zip/Postal Code:
For fastest response contact us at: or call us toll-free at: +1-800-858-TEST (8378) Tel: +1-847-367-4077 Fax: +1-847-367-4080 E-mail: [email protected]
At Associated Research, Electrical Safety Compliance Testing Is Our Only Focus!
Our Products Include:
Hipot Testers
Line Leakage Testers
Insulation Resistance Testers
Ground Bond Testers
Functional Run Testers
HV/HC Scanning Matrices
Custom Instruments
Our Services Include:
Software Programs
Customized System Design
Knowledgeable Customer Support
Expert Technical Services
Industry Seminars
Educational Programs
Local Sales Offices
13860 West Laurel Drive, Lake Forest, IL U.S.A. 60045 Tel: +1-847-367-4077 Fax: +1-847-367-4080 E-mail: [email protected]
For more information visit us at or call us toll-free at 1-800-858-TEST (8378)
Catalog# GUIDE 7/04
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