Simpson 270 Series 5 Volt-Ohm-Milliammeter

Simpson 270 Series 5
Volt-Ohm-Milliammeter
INSTRUCTION MANUAL
SIMPSON ELECTRIC COMPANY 520 Simpson Avenue
Lac du Flambeau, WI 54538-0099 (715) 588-3311 FAX (715) 588-3326
Printed in U.S.A.
Part No. 06-111642 Edition 14, 05/07
Visit us on the web at: www.simpsonelectric.com
32
About this Manual
To the best of our knowledge and at the time written, the information contained in
this document is technically correct and the procedures accurate and adequate
to operate this instrument in compliance with its original advertised specifications.
NOTES
Notes and Safety Information
This Operator’s Manual contains warning symbols which alert the user to check
for hazardous conditions. These appear throughout this manual where applicable, and are defined below. To ensure the safety of operating performance of
this instrument, these instructions must be adhered to.
!
Warning, refer to accompanying documents.
Caution, risk of electric shock.
Technical Assistance
SIMPSON ELECTRIC COMPANY offers assistance Monday through Friday
8:00 am to 4:30 pm Central Time. To receive assistance contact Technical Support or Customer Service at (715) 588-3311.
Internet: http://www.simpsonelectric.com
Warranty and Returns
SIMPSON ELECTRIC COMPANY warrants each instrument and other articles
manufactured by it to be free from defects in material and workmanship under
normal use and service, its obligation under this warranty being limited to making
good at its factory or other article of equipment which shall within one (1) year
after delivery of such instrument or other article of equipment to the original
purchaser be returned intact to it, or to one of its authorized service centers, with
transportation charges prepaid, and which its examination shall disclose to its
satisfaction to have been thus defective; this warranty being expressly in lieu of
all other warranties expressed or implied and of all other obligations or liabilities
on its part, and SIMPSON ELECTRIC COMPANY neither assumes nor authorizes any other persons to assume for it any other liability in connection with the
sales of its products.
This warranty shall not apply to any instrument or other article of equipment
which shall have been repaired or altered outside the SIMPSON ELECTRIC
COMPANY factory or authorized service centers, nor which has been subject to
misuse, negligence or accident, incorrect wiring by others, or installation or use
not in accord with instructions furnished by the manufacturer.
2
31
NOTES
NOTES
30
3
Contents
6.3
Schematic Diagram
1. INTRODUCTION ............................................................................... 7
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
General Description ............................................................................. 7
Overload Protection ............................................................................. 7
Internal Batteries .................................................................................. 8
Printed Circuit ....................................................................................... 8
Phenolic Case ...................................................................................... 8
Adjust-A-Vue Handle ............................................................................ 8
Test Leads ............................................................................................ 8
Technical Data ...................................................................................... 8
Definition of Accuracy ........................................................................ 10
Safety Considerations ........................................................................ 10
2. INSTALLATION ................................................................................ 11
2.1
2.2
2.3
2.4
Unpacking and Inspection ................................................................. 11
Warranty ............................................................................................. 11
Shipping ............................................................................................. 11
Power Source Requirements .............................................................11
3. CONTROLS, JACKS AND INDICATORS ......................................... 12
3.1
Front Panel Description ......................................................................12
4. OPERATION .................................................................................... 13
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
4.19
Safety Precautions .............................................................................13
Polarity Reversing ..............................................................................14
Measurement Of Unknown Voltage Or Current .................................15
Test Leads ..........................................................................................15
DC Voltage Measurement 0-250 Mv Range ...................................... 15
DC Voltage Measurement 0-1V Range ............................................. 15
DC Voltage Measurement 0-2.5 Through 0-500V Range. ................. 16
DC Voltage Measurement 0-1000v Range ........................................16
AC Voltage Measurement 0-2.5 Through 0-500V Range .................. 17
AC Voltage Measurement 0-1000V Range .......................................18
Output Voltage Measurement .............................................................19
Decibel Measurement (-20 to +50 dB) .............................................. 20
Direct Current Measurement ..............................................................21
Direct Current Measurement 0-50 µA Range .................................... 21
Direct Current Measurement 0-1mA through 0-500mA Range ......... 21
Direct Current Measurement 0-10A Range .......................................22
Zero Ohms Adjustment .......................................................................23
Measuring Resistance .......................................................................23
Resistance Measurement of Semiconductors ................................... 24
5. OPERATOR SERVICING ................................................................. 25
5.1
5.2
5.3
5.4
5.5
Inspection ........................................................................................... 25
Battery Replacement .......................................................................... 25
Fuse Replacement .............................................................................26
Test Lead Inspection .......................................................................... 26
Care ....................................................................................................26
6. SERVICING INSTRUCTIONS .......................................................... 27
6.1
6.2
6.3
Removing the Instrument Case ......................................................... 27
Replacement Parts .............................................................................27
Schematic Diagram ............................................................................ 29
4
Figure 6-1. Schematic Diagram
29
Reference
Symbol
R16
R17
R18
R19
R20
R21
R23, R24
R26
R27
R28
R29
R30
C1
D1, D2
V1
F1
F2
Description
Resistor, 11⍀, 5W
(Wire Wound)
Resistor, 1.095 k⍀
Resistor, 138⍀
Resistor, 17.320 k⍀
Resistor, 113.860 k⍀
Potentiometer
11.25 k⍀
Resistor, 4 k⍀
Resistor, 7.5 k⍀
Resistor, 37.5k⍀
Resistor, 200 k⍀
Resistor, 1 M⍀
Resistor, 1.25 M⍀
Capacitor, 0.1 µF,400V
Diode, Germanium
Diode 1N914 (2)
Fuse, 1 Amp, 250V;3AG
(1-1/4” x 1/4”)
Quick acting
(Littlefuse Type 312001)
Part No.
6-111979
6-111639
6-111640
6-111638
6-111637
6-111446
1-117140
1-117152
1-117145
1-117146
1-117150
5-110455
1-113733
1-115970
5-112004
1-112507
Reference
Symbol
Description
NOTES
(Bussman Type BBS or 5-119056
Littlefuse Type BLS)
For Function Switch
1-115789
Knobs: For Zero Ohms
Adjust
1-115790
For Range Switch
10-864352
Case Assembly, Phenolic,
Complete, including
Handleless Battery
Compartment Front
Cover
10-864996
Cover Assembly
10-861724
Rubber Bumper Plug
5-115039
270-5 and 270-5RT
Indicating Instrument
w/ Panel Assembly
D-13824
Cover Assembly for
Indicating Instrument
10-560288
Probe Tip Leads,
one red and one black 00043
Label, Battery and
Fuse Data
06-111498
Fuse, 2A, 600V
28
5
NOTES
d.
e.
f.
6.
Verify Instrument accuracy by performing operational checks using known,
accurate, stable sources. If proper calibration equipment is not available,
contact the nearest Authorized Service Center. If the Instrument has not
been used for 30 days, check the batteries for leakage and replace if necessary.
It is recommended that the Instrument be returned annually to the nearest
Authorized Service Center, or to the factory, for an overall check, adjustment,
and calibration.
When not in use, store the Instrument in an environment free from temperature extremes, dust, corrosive fumes, and mechanical vibration or shock. If
storage time is expected to exceed 30 days, remove batteries.
SERVICING INSTRUCTIONS
This Instrument must be serviced by qualified personnel. To aid in troubleshooting, a schematic diagram is available on page 29. The replacement parts list
(Table 6-1) describes the components and refers to Simpson part numbers. Reference Symbol numbers on the replacement parts list correlate with the components shown on the schematic diagram.
The following information is provided as an adjunct to the overall text contained
in this manual and should be read and understood thoroughly before ordering
replacement parts for the Instrument.
6.1
Removing the Instrument Case
To open the Instrument panel, first de-energize and disconnect the test leads,
and remove the cover from the battery compartment. Remove the four casefastening screws and lift the case from the panel.
When replacing the case, make certain that the wires leading to the battery compartment are seated in their respective slots within the compartment wall. This
will prevent damage to the wire insulation.
6.2
Replacement Parts
To obtain replacement parts, address order to the nearest Authorized Service
Center. Refer to paragraph 2.2 for ordering instructions.
Table 6-1. Replacement Parts
6
Reference
Symbol
Description
Part No.
R1
R1A
R2, R22, R25
R2A
R3
R4
R5
R6
R7
R8
R9
Rheostat, 150 k⍀
Resistor, 20 k⍀
Rheostat, 3 k⍀
Resistor, 2.2 k⍀
Resistor, 15 k⍀
Resistor, 45 k⍀
Resistor, 150 k⍀
Resistor, 800 k⍀
Resistor, 4 M⍀
Resistor, 5 M⍀
Resistor, 7.5 M⍀
6-111487
5-119705
6-111488
5-118606
5-115082
1-117148
1-117149
1-117147
1-117151
1-118181
5-115081
27
Reference
Symbol
R10
R11
R12
R13
R14
R15
Description
Resistor, 2.5 Mk⍀
Resistor 0.025⍀
Shunt 10A
(Calibrate in Instrument)
Resistor, 0.47⍀ 5W
(Wire Wound)
Resistor, 2⍀ 5W
(Wire Wound)
Resistor, 22.5⍀ 3W
(Wire Wound)
Resistor, 238⍀
5-115080
6-111575
6-111980
6-111810
6-111809
1-115079
a.
b.
c.
d.
5.3
Two batteries are used to supply power for resistance measurements, a 1.5V
D and a 9V battery. When it is no longer possible to adjust the pointer to zero
for the R x 1 and R x 100 ranges (refer to ZERO OHMS ADJUSTMENT
paragraph 4.17) replace the 1.5V battery. When it is no longer possible to
adjust the pointer to zero on the R x 10,000 range, replace the 9V battery.
Recommended replacement batteries are a 1.5V, D size, NEDA 13F and a
9V, NEDA 1604.
To install or replace a battery, de-energize and disconnect test leads from the
Instrument, then remove the cover to the externally accessible battery compartment by loosening the single captivated screw.
Observe polarity when replacing the 1.5V D battery and connect as indicated. The D battery is held in place with spring clips which also act as
battery contact clips. The 9V battery contacts and connector are polarized.
To remove the 9V battery, first withdraw battery with mated connector from
the compartment, then remove connector.
1.
INTRODUCTION
1.1
General Description
The Simpson Volt-Ohm-Milliammeter 270 Series 5 is a rugged, accurate, compact and easy-to-use instrument that will make accurate measurements of AC
and DC voltage, direct current, resistance, decibels, and output voltage. The
output voltage function is used for measuring the AC component of a mixture of
AC and DC voltage. This occurs primarily in amplifier circuits.
New Features for the 270 are:
New connectors between the Instrument and the test leads, eliminating a
shock hazard if a connector is inadvertently pulled out of the Instrument jack.
An OFF/TRANSIT position, which is added to the function switch to protect
the meter movement during transit. (This position shunts the meter movement and opens the internal connections to the COMMON and + jacks.)
Fuse Replacement
The 1 and 2 Amp fuses (also the 1A spare) are located in the externally accessible battery and fuse compartment. Access compartment by de-energizing and
disconnecting the test leads and loosening the single captivated screw on the
compartment cover. To replace or check a fuse, apply pressure to the 1 amp fuse
cup then rotate the plate to expose a selected fuse for removal from the panel’s
cavity.
Replace the 1 and 2 ampere fuse with the specified fuse type only. (See replacement parts list, Table 6-1, for proper fuse type.)
5.4
Test Lead Inspection
Periodic inspection of the test leads is recommended to detect cuts, burned areas, deterioration or other damage that could reduce the insulation strength of
the leads.
!
Before returning the Instrument for service, check the performance and make
sure that the electrical and mechanical configurations have been restored to their
original ratings and condition.
5.5
Care
a.
b.
c.
Immediately clean all spilled materials from the Instrument and wipe dry. If
the spillage is corrosive, use a suitable cleaner to neutralize the corrosive
action, and remove the spillage.
When the Instrument is not in use, rotate the function switch to the OFF/
TRANSIT position.
Avoid prolonged exposure or usage in areas subject to temperature and
humidity extremes, vibration or mechanical shock, dust or corrosive fumes,
or strong electrical or electromagnetic fields.
26
A test lead set with molded elbow plugs at one end for connection to the front
panel input terminals and test probes at the other end. The test probes have
a non-slip grip surface and a barrier to maintain the spacing between the
user’s fingers and the probe tip. Threaded shoulders at the probe tip accept
screw-on alligator clips (supplied) or an accessory AC or DC 5000 volt range
extending probes.
1.2
Overload Protection
No single protective device nor even a combination of devices as found in the
270 can fully protect a multipurpose instrument under all overload conditions.
Despite all the built-in-protection provided, however, severe overloads can damage the Instrument when the Instrument is misused. The fuse/varistor combination in the 270 has been designed to afford maximum instrument protection under foreseeable overload conditions which might occur within the measuring
capabilities of the Instrument. However, the operator must use care to avoid
severe overloads, particularly when working in high voltage circuits.
a.
Fuses: Basic overload protection is provided by a small, inexpensive and
easily obtainable 3 AG type, 1 ampere, quick-blow fuse. This fuse is rated to
interrupt circuit voltages up to 250 volts. A supplemental high energy fuse is
provided for additional protection from severe overloads. This fuse is the
Bussman Type BBS 2A 600 V and has an interruption capacity of 10,000
amps AC. The Littlefuse Type BLS 2A 600 V with an interrupt capacity of
100,000 amps AC may also be used.
b. For maximum protection replace the 1A fuse with a Littlefuse Type 312001
only. This will allow the combination 1A and 2A fuse to give maximum protection to the unit and user under overload conditions which may occur within
the measuring capability of the VOM.
c. If the Instrument fails to indicate, the 1 Amp or the 2 Amp fuse may be burned
out. (Refer to paragraph 5.3 for fuse replacement.) A 1 Amp spare fuse is
furnished with each Instrument. Fuses are located in the battery and fuse
compartment.
NOTE: The 0-10A range is not fused. The shunt connects directly to the -10A and
+10A jacks.
d. Two diodes connected across the meter movement afford protection to the
movement by circumventing excessive current around the movement in the
event of an overload.
7
1.3
5.
Internal Batteries
There are two batteries in the ohmmeter circuits, a NEDA 13F size D cell that
furnishes 1.5-volts for the R x 1 and R x 100 ranges and a NEDA 1604 battery that
furnishes 9-volts for the R x 10,000 range.
1.4
Printed Circuit
The following paragraphs describe the battery replacement, fuse replacement,
test lead inspection and care for the 270-5.
5.1
Phenolic Case
Make certain that the battery compartment cover is securely fastened in place
before the Instrument is used.
The Phenolic case is designed with heavy reinforced walls for maximum durability and provides excellent protection for the circuit components. The case also
has an externally accessible battery and fuse compartment. Access to the batteries and fuses is obtained by unscrewing a single captivated screw at the bottom
of the case and sliding out the compartment cover.
1.6
Do not permit an Instrument with a broken glass meter cover to be used.
Whenever the battery compartment cover is removed for any reason, check that
the proper fuses are being used.
Severe overloads may have damaged the Instrument’s circuitry despite the protection afforded by the fuse. When a fuse is replaced, all ranges should be
routinely checked (calibrated) against the specifications in this manual before
the Instrument is returned to service.
Adjust-A-Vue Handle
A carrying handle is attached to the Instrument case. The handle may be used to
support the Instrument in a convenient sloping position for easy viewing. The
case can also be placed either vertically or horizontally. The horizontal position is
preferable for greater accuracy since the Instrument is calibrated in this position.
1.7
Test Leads
Each Instrument is furnished with one pair (Catalog Number 00043) of probe
type test leads (one red and one black, each 48 inches long) for all applications
of the Instrument. These test leads have elbow prods on one end to connect the
leads to the recessed jacks on the Instrument front panel. The probe tips at the
opposite end have threaded shoulders to accept the screw-on insulated alligator
clips (furnished with the test leads) or the 5000 volt test probe(s) to extend the
Instrument AC or DC voltage range. The test leads and the insulated alligator
clips are rated for the voltage and current ranges available on the 270. Maximum
ratings are 1000 V AC or DC or 10 DC amperes. These ratings for the test leads
must not be exceeded in any application.
1.8
Inspection
The user is protected from electrical shock by the insulation of the 270 and its test
leads. Frequently examine the 270 and its test leads for insulation damage. Check
for cracks, cuts, chips, burns or deterioration that expose internal metal parts or
reduce the spacing between such metal parts and hand contact.
Most of the component parts are mounted on a printed circuit board which simplifies assembly and maintenance, thus extending the useful life of the Instrument.
1.5
OPERATOR SERVICING
5.2
Battery Replacement
Batteries should be replaced before their useful life has expired. Failure to do so
may result in battery leakage and corrosion.
2A FUSE
SPARE 1A FUSE
9V BATTERY
1A FUSE
Technical Data
Table 1-1. Technical Data
1.
2.
3.
DC VOLTS:
Ranges:
Sensitivity:
0-1-2.5-10-50-250-500-1000V
20,000V per volt
DC MILLIVOLTS:
Range:
Sensitivity:
0-250mV
20,000V per volt
AC VOLTS:
Ranges:
Sensitivity:
0-2.5-10-50-250-500-1000V
5,000⍀ per volt
8
Figure 5-1. Battery and Fuse Compartment
25
Note: The OHMS scale reads from right to left for increasing values of resistance.
e.
4.19
4.
To determine the actual resistance value, multiply the reading by the factor at
the switch position. (K on the OHMS scale equals one thousand.)
5.
Resistance Measurement of Semiconductors
6.
7.
Make sure that the OHMS range being used will not damage any of the semiconductors (refer to Table 1-1, item 8, Section 1).
If there is a “forward” and “backward” resistance such as in diodes, the resistance
should be relatively low in one direction (for forward polarity) and higher in the
opposite direction.
Rotate the function switch between the two DC positions to reverse polarity. This
will determine if there is a difference between the resistance in the two directions.
To check a semiconductor in or out of a circuit (forward and reverse bias resistance measurements) consider the following before making the measurement:
a.
b.
c.
NOTE: The resistance of diodes will measure differently from one resistance
range to another on the same VOM with the function switch in a given position.
For example, a diode which measures 80 ohms on the R x 1 range may measure
300 ohms on the R x 100 range. The difference in values is a result of the diode
characteristics and is not indicative of any fault in the VOM.
0-2.5-10-50-250 (limited to 350 VDC)
0-50µA
250 mV
0-1-10-100-500 mA
250 mV, 255 mV, 300 mV, 500 mV
0-10A
255 mV
NOTE: The 10A range is not internally fused.
8.
The polarity of the internal ohmmeter battery voltage at the (+) positive jack is
identical to the function switch, polarity setting, and opposite to the (-) common jack.
Make sure that the OHMS range being used will not damage any of the
semiconductors (refer to Table 1-1, item 8, Section 1).
If the semiconductor is a silicon diode or conventional silicon transistor, precautions are not normally required.
If the semiconductor material is germanium, check the ratings of the device
and refer to Table 1-1, item 8.
OUTPUT VOLTAGE (AC):
Ranges:
DC MICROAMPERES:
Range:
Voltage Drop:
DC MILLIAMPERES:
Ranges:
Voltage Drop (Approx.):
DC AMPERES:
Range:
Voltage Drop (Approx.):
RESISTANCE
RX1
R X 100
R X 10,000
Range:
0-2000⍀
0-200,000⍀
0-20 M⍀
Center Reading:
12⍀
1200⍀
120,000⍀
Nominal Open Circuit
Voltage
1.5V
1.5V
9V
Nominal Shor t Circuit
Current
125mA
1.25mA
75µA
9.
*ACCURACY:
DC Voltage Ranges:
DC Current
0-50µA Range:
Other Ranges:
**AC Voltage Ranges:
Frequency Response:
Resistance Ranges:
R x 1:
R x 100:
R x 10,000:
10. DECIBELS:
Ranges:
Reference Level:
11. BATTERIES:
12. FUSES:
13.
14.
15.
16.
TEST LEADS:
SIZE:
WEIGHT:
***RATED CIRCUIT-TO
-GROUND VOLTAGE:
77°F
1.25% of F.S.
.75% F.S.
1.25% of F.S.
1.25% of F.S.
1.75% of F.S.
2% of F.S.
3% of F.S.
Referenced to 100 Hz (Figures 4-2 and 4-4)
1.5% of Arc
1° of Arc
1° of Arc
1.75° of Arc
1.25° of Arc
1.25° of Arc
-20 to +10 dB, -8 +22dB, +6 to +36 dB, +20 to
+50 dB
W/zero power level equal to 1 mW across
a 600⍀ line.
1.5V, D Size, NEDA 13F 9V, NEDA 1604
F1: 1A, 250V, type 3AG, quick-acting Littlefuse
Type 312001, F2: 2A, 600V (Bussman Type
BBS or Littlefuse Type BLS)
1 red, 1 black, 48” long.
5-1/2” x 7” x 3 1/8” (13.34 x 17.78 x 7.94 cm)
3 lbs. (1.359 kg)
1000V AC/DC Max.
*Accuracies specified are for the 270 in a horizontal position.
24
67°-87°F
1.75% of F.S.
9
**Responds to the average value of an AC current, and is calibrated to indicate
the RMS value of a pure sine wave.
***Per ANSI C39.5 April 1974: “The maximum voltage, with respect to Ground,
which may safely and continuously be applied to the circuit of an Instrument.”
1.9
Definition of Accuracy
The voltage and current accuracy of this Instrument is commonly expressed as a
percent of full scale. This should not be confused with accuracy of reading (indication). For example, +2% of full scale on the 10 volt range allows an error of
±0.20V at any point on the dial. This means that at full scale, the accuracy of
reading would be ±2%, but at half scale it would be ±4%. Therefore, it is advantageous to select a range which gives an indication as near as possible to full
scale.
1.10
Safety Considerations
This Operator’s Manual contains special caution and warning symbols which
alert the user to hazardous operating and servicing conditions. These symbols
appear throughout this publication, where applicable, and are defined on the
inside front cover of this manual under NOTES AND SAFETY INFORMATION.
These instructions must be adhered to in order to ensure the safety of operating
and servicing personnel and to retain the operating conditions of the Instrument.
Table 1-2. Items and Accessories Furnished with this Instrument
Quantity
1
*1
*1
2
1
1
Description
Test Lead Set, one red and one
black (48” long) each with combination
probe tip and removable rubber-sleeved
alligator clip.
1.5 volt, D cell, NEDA 13 F
9.0 volt Cell, NEDA 1604
1 Amp, 250 V Fuse, Littlefuse Type #312001
2 Amp Fuse, 600 V (Bussman Type BBS or
Littlefuse Type BLS)
Operator’s Manual
Number
00043
4.17
When resistance is measured, the INTERNAL batteries B1 and B2 furnish power
for the circuit. Since batteries are subject to variation in voltage and internal
resistance the Instrument must be adjusted to zero before measuring a resistance, as follows:
a.
b.
c.
d.
e.
4.18
a.
6-111642
c.
d.
10
Measuring Resistance
When making in-circuit measurements, circuit paths in parallel with the resistance being measured may cause reading errors. Check circuit diagrams for the
presence of such components before assuming that the reading obtained is
correct.
b.
Catalog Number
00812
00805
00414
00545
Turn range switch to desired ohms range.
Plug the black test lead into the - COMMON jack and the red test lead into the
+ jack.
Connect ends of test leads together to short the VOM resistance circuit.
Rotate the ZERO OHMS control until pointer indicates zero ohms. If pointer
cannot be adjusted to zero, one or both of the batteries must be replaced.
(For battery replacement refer to Section 5.)
Disconnect shorted ends of test leads.
Voltage applied to a resistance range will cause reading errors if low and damage the Instrument if high. When making in-circuit measurements, make certain
that the circuit is completely de-energized before making connections to it.
*Batteries are standard items replaceable from local retail stores.
Table 1-3. Additional Accessories
Description
Deluxe Case
Leatherette Ever-Redy Hard Case, Drop Front
Low-Power Ohm Probe
Model 150-2 Amp-Clamp
Zero Ohms Adjustment
Before measuring resistance in the
circuit make sure the power is off in
the circuit being tested and all capacitors discharged.
Disconnect the shunted component
from the circuit before measuring its
resistance. Then set the range switch
to one of the resistance range positions as follows (Figure 4-8):
1. Use R x 1 for resistance readings from 0 to 200⍀.
2. Use R x 100 for resistance readings from 200 to 20,000⍀.
3. Use R x 10,000 for resistance
readings above 20,000⍀.
Set the function switch at either - DC
or + DC position. Operation is the
same in either position except if semiconductors are in the circuit. (See
paragraph 4.19) Adjust ZERO
OHMS control for each resistance
range.
Observe the reading on the OHMS
scale at the top of the dial.
23
WARNING
READ MANUAL BEFORE USE
+D.C.
-D.C.
RX1
RX100
RX10,000
COMMON
270
ALL TERMINALS 1KV. MAX
Figure 4-8. Jacks and Switch
Positions for Measuring
Resistance
c.
d.
e.
f.
g.
h.
4.16
Set the range switch at one of the four
range positions marked 1 mA, 10 mA,
100 mA, or 500 mA.
Turn OFF power. Discharge any capacitors in circuit.
Open the grounded side of the circuit
in which the current is being measured. Connect the VOM in series with
the circuit. Connect the red test lead
to the positive side and the black test
lead to the negative side.
Turn the power on. Read the current
in milliamperes on the black DC scale.
For the 1mA range, use the 0-10 figures and divide by 10. For the 10mA
range, use the 0-10 figures directly. For
the 100mA range, use the 0-10 figures and multiply by 10. For the 500mA
range, use the 0-50 figures and multiply by 10.
Turn the power off and disconnect the
test leads.
Restore circuit to original condition.
2.
This section contains information and instructions for the installation and shipping of the Simpson 270-5. Included are unpacking and inspection procedures,
warranty, shipping and power source requirements.
2.1
READ MANUAL BEFORE USE
+50 ⌽AMPS.
250MV.
-10A.
+D.C.
-D.C.
Unpacking and Inspection
Examine the shipping carton for signs of damage. If damaged, notify the carrier
and supplier and do not attempt to use the Instrument.
WARNING
500MA.
If Instrument appears to be in good condition, read Operator’s Manual in its entirety.
+10A.
100MA.
10MA.
AMPS
Become familiar with the Instrument as instructed in the manual, then check the
electrical performance as soon as possible. Check that all items are included
with the Instrument (Table 1-2).
1MA.
50V.
⌽AMPS.
COMMON
270
After unpacking the Instrument, a 1.5V battery and a 9V battery may be found in
separate envelopes in the box with the Instrument and test leads. Two alligator
clips for the test leads are in a polyethylene bag. (See Section 5 for instructions
on how to open the battery compartment and install the batteries.)
ALL TERMINALS 1KV. MAX
Figure 4-7. Jacks and Switch
Positions for Measuring Direct
Current
2.2
The 10A range is not internally fused in the 270.
When using the 10A range, never disconnect a test lead from a jack or from the
circuit while the circuit is energized. Doing so may damage the test jacks or leads
and the arcing may be hazardous to the operator. Turn off circuit power and wait
for the meter reading to drop to zero.
The polarity reversing feature of the function switch does not operate on the 010A range. If polarity is found to be incorrect, turn off circuit power, wait for the
meter indication to read zero and then interchange test lead connections to the
circuit.
a. Plug the black test lead into the -10A jack and the red test lead into the +10A
jack.
b. Set the range switch at 10 AMPS (dual position with 10mA).
c. Turn the power OFF. Discharge any capacitors in the circuit.
d. Open the ground side of the circuit in which the current is being measured.
Connect the VOM in series with the circuit. Connect the red test lead to the
positive side and the black test lead to the negative side.
NOTE: The function switch has no effect on polarity for the 10 AMPs range.
e. Turn the power on. Read the current directly on the black DC scale. Use the
0-10 figures to read directly in amperes.
f. Turn the power off and disconnect the test leads.
g. Restore circuit to original condition.
Warranty
The Simpson Electric Company warranty policy is printed on the inside front
cover of this manual. Read the warranty policy carefully before requesting any
warranty repairs. For all assistance, including help with the Instrument under
warranty, contact the nearest Authorized Service Center for instructions. If necessary, contact the factory directly and give full details of any difficulty and include the Instrument model number, series number, and date of purchase. Service data or shipping instructions will be mailed promptly. If an estimate of charges
for non-warranty or other service work is required, a maximum charge estimate
will be quoted. This charge will not be exceeded without prior approval.
Direct Current Measurement 0-10A Range
22
INSTALLATION
2.3
Shipping
Pack the Instrument carefully and ship it prepaid and insured.
2.4
Power Source Requirements
There are two batteries in the ohmmeter circuits, a NEDA 13F D size cell that
furnishes 1.5 volts for the R x 1 and R x 100 ranges and a NEDA 1604 battery that
furnishes 9 volts for the R x 10,000 range.
11
3.
CONTROLS, JACKS AND INDICATORS
All operating and adjustment controls, jacks and indicators for the Simpson 2705 are described in this section. Become familiar with each item before operating
the Instrument.
3.1
Front Panel Description
The front panel controls, jacks and indicators are described in Table 3-1 and illustrated in Figure 3-1.
Table 3-1. Controls, Jacks and Indicators
1.
2.
3.
Front Panel:
The 270-5 Volt-Ohm-Milliammeter is a large, easy-toread 4-1/4” indicating Instrument. Switch positions
and circuit jacks are marked in white characters for
easy reading.
The range switch may be rotated in either direction to
select the desired voltage, current, or resistance range
position.
The function switch has four positions: Off/Transit, +DC,
-DC and AC. To measure DC current or voltage, set
the function switch at the -DC or +DC position, depending on polarity of the signal applied across test
leads. To measure AC voltage set the function switch
to the AC position. For resistance measurement, the
switch may be set in either the +DC or -DC position.
The polarity of the internal ohmmeter battery voltage
at the (+) positive jack is identical to the function switch
polarity setting and opposite at the (-) common jack.
Range Switch:
Function Switch:
VOLTAGE RANGE
dB RANGE
READING
0-2.5V
-20 to +10
Read directly
0-10V
-8 to +22
Add +12 dB to reading
0-50V
+6 to +36
Add +26 dB to reading
0-250V
+20 to +50
Add +40 dB to reading
NOTE: The maximum voltage ratio that can be measured is +50 dB on the 0-250V
range.
e. If dB measurement is being made to a 0.0006 watt into 500 ohm reference
level, subtract +7 dB from the reading obtained on the 270-5.
4.13
a.
b.
c.
d.
e.
4.14
Direct Current Measurement
!
Do not change the setting of the range or change the function switches while
circuit under measurement is energized.
Never disconnect test leads from circuit under measurement while the circuit
is energized.
Always turn the circuit power off and discharge all the capacitors before
setting the switches or disconnecting the leads.
Never exceed the circuit-to-ground voltage of the instrument (1000V MAX.,
Table 1-1, Item 16).
Always connect the Instrument in series with the ground side of the circuit.
Direct Current Measurement 0-50 µA Range
a.
b.
Set the function switch at + DC.
Plug the black test lead into the - COMMON jack and the red test lead into the
+50µA/250mV jack.
c. Set the range switch at 50µA (dual position with 50V).
d. Turn OFF power. Then discharge any capacitors in the circuit.
e. Open the ground side of the circuit in which the current is being measured.
Connect the VOM in series with the circuit. Connect the red test lead to the
positive side and the black test lead to the negative side.
f. Turn ON power.
g. Read the current on the black DC scale. Use the 0-50 figures to read directly
in microamperes.
h. Turn power OFF and restore circuit to original condition.
NOTE: For polarity reversing see paragraph 4.2.
WARNING
READ MANUAL BEFORE USE
A.C.
2.5V.
1V.
10V.
50V.
␮AMPS
250V.
500V.
COMMON
COMMON
1000V
1000V.
270
A.C.
D.C.
ALL TERMINALS IKV. MAX
Figure 3-1. Controls, Indicators and Connector
12
4.15 Direct Current Measurement 0-1mA through 0-500mA
Range
a.
b.
Set the function switch at + DC (Figure 4-7).
Plug the black test lead into the - COMMON jack and the red test lead into the
+ jack.
21
d.
e.
f.
Turn OFF power.
Connect the test leads across the circuit being measured with the black
test lead to the ground side.
Turn on power in the test circuit. Read
the output voltage on the appropriate AC voltage scale. For the 0-2.5V
range, read the value directly on the
scale marked 2.5 VAC. For the 10V,
50V, or 250V ranges, use the red scale
marked AC and read the black figures immediately above the scale.
4.
Zero Ohms:
5.
Circuit Jacks:
6.
Pointer Adjust:
for Zero:
WARNING
READ MANUAL BEFORE USE
A.C.
2.5V.
IV.
10V.
50V.
␮AMPS
250V.
OUTPUT
COMMON
270
350 VDC
MAX
ALL TERMINALS IKV. MAX
Figure 4-5. Jacks and Switch for
Output Measurement
4.12
Decibel Measurement (-20 to +50 dB)
Some industries measure in terms of voltage or current ratios (decibels) based
on a specific reference level. The dB scale on the 270 serves this purpose and is
calibrated to a reference level (zero dB) or 0.001 watt into 600 ohms. The scale
calibration of -20 to +10 dB is for the 0-2.5V range (zero dB = 0.775V). Higher
ranges may be used by adding an appropriate dB value to the reading in accordance with chart on the following page.
a.
b.
c.
c.
Review the safety precautions in
paragraph 4.1.
Set the functions switch at AC (figure
4-6).
Plug the black test lead into the COMMON jack and the red test lead
into the + jack.
Use operating instructions for AC
VOLTAGE MEASUREMENT, 0-2.5/
10/50/250/500V RANGES (paragraph 4.9).
Read decibels on the bottom scale
marked dB. For the 10/50/250V
ranges, add the appropriate factor
from the following chart.
OPERATION
This section contains information required to operate the 270-5 safely and properly.
Multifunction Instruments, (VOM’s), such as the 270-5 are intended as general
purpose measuring instruments for use in low power circuitry such as found in
consumer appliances, TV and radio receivers, and in general laboratory applications. Their use is not recommended in high voltage, high power circuitry where
operator errors and inadequate personal protective measures could result in
serious injury from arcing or explosion. Such circuitry is found in industrial or
commercial applications such as induction (r-f) heaters and broadcast transmitters, power substations and distribution centers, x-ray equipment, large motor
controls, etc. Working in the high voltage section of such equipment requires
single-function, often specially designed, instruments operated by specially
trained personnel who use appropriate protective equipment and procedures.
WARNING
READ MANUAL BEFORE USE
A.C.
2.5V.
1V.
10V.
50V.
␮AMPS
250V.
COMMON
COMMON
4.1
270
ALL TERMINALS IKV. MAX
Figure 4-6. Jacks and Switch
Positions for Measuring Decibels
20
With the Volt-Ohm-Milliammeter in an operating position, check that the pointer indicates zero at the left
end of the scale when there is no input. If pointer is off
zero, adjust the screw located in cover below the center of the dial. Use a small screwdriver to adjust the
screw until the pointer rests freely over the zero mark
at the left end of the scale. This procedure will avoid
disturbances to the zero setting by subsequent
changes in temperature, humidity, vibration, and other
environmental conditions.
!
Do not use the 500V range for decibel
readings.
d.
4.
Off/Transit Position: This function switch position opens
the 270 common and + jack inputs to avoid accidental
instrument overload or internal battery drain. It also
shunts the sensitive instrument during transit to provide damping during non-use periods.
This control is used to compensate for variation in the
voltage of internal batteries.
There are eight jacks on the front panel marked with
the functions they represent (Fig. 3-1). These jacks
provide electrical connections to the test leads. The
COMMON (-) jack is used (in conjunction with black
test lead) as the reference point for measurement of
all the functions with the exception of the 10A range.
(Refer to Section 5, Operator Servicing.)
Safety Precautions
The following precautions are commonly recognized safe practices to adopt and
specific hazards to avoid, and are not implied to be sufficient to safeguard untrained personnel in all circumstances. Neither is this manual a substitute for
technical manuals covering the equipment in which measurements are to be
made. Always refer to the equipment manual and its specific warnings and
instructions and observe them as well as those contained herein.
13
b.
c.
d.
The 270 should only be used by personnel qualified to recognize shock
hazards and who are trained in the safety precautions required to avoid
possible injury.
Do not connect any terminal of this Instrument to a circuit point at which a
voltage exceeding 1000 volts AC or DC may exist with respect to earth
ground. (Refer to Table 1-1, item 16.)
Turn off power and discharge any capacitors in the circuit to be measured
before connecting to or disconnecting from the circuit.
Before using this Instrument, check accessories (if any) and test leads for
missing, damaged, deteriorated or otherwise faulty insulating parts. Do not
use, or permit the use of, equipment with faulty insulation until it has been
properly repaired.
!
e.
f.
Always wear safety glasses when working in electrical circuitry.
Do not work alone on high voltage circuits. Make certain that someone
capable of giving aid is nearby and alert to potential problems.
g. Do not handle the instrument, test leads, or circuitry while high voltage is
being applied.
h. Hands, shoes, floor, and workbench must be dry. Avoid measuring under
humid, damp, or other environmental conditions that could affect the dielectric withstanding voltage of the test leads or Instrument.
i. Do not change switch settings or test lead connections while the circuit is
energized. A mistake could damage the Instrument or cause personal injury.
j. Locate all voltage sources and accessible current paths before making connections to circuitry. Voltage may appear unexpectedly or in unexpected
locations in faulty equipment. An open bleeder resistor, for example, may
result in a capacitor retaining a dangerous charge.
k. Make certain that the equipment being worked on is properly grounded and
fuses are of the proper type and rating.
l. Double check switch positions and jack connections before applying power
to the Instrument.
m. Remain alert for low voltage circuits which may be floating at high voltage
with respect to earth ground and for composite voltages (AC + DC) such as
are found in r-f amplifiers. The floating voltage or composite voltage must not
exceed the Instrument’s rated maximum circuit-to-ground voltage.
n. Do not measure where the air may contain explosive concentrations of gas
or dust such as in mines, grain elevators, gasoline stations or in the presence of charging batteries until determined to be safe by qualified personnel.
Note that even metallic dusts can be explosive.
o. No general purpose VOM is to be used to make electrical measurements on
blasting circuits or blasting caps. Use VOMs designed for this purpose only.
4.2
Polarity Reversing
The function switch provides a convenient means to reverse polarity of the internal battery to facilitate testing semiconductor devices. The +DC and -DC positions transpose internal connections to the COMMON and + jacks and therefore
can also be used to reverse polarity of external voltages and currents connected
to these jacks (only). Because polarity reversing momentarily interrupts the circuit, it should not be done while measuring current without first turning off the
14
!
Turn off power to the circuit and wait until the meter indicates zero before disconnecting the test leads.
4.11
Output Voltage Measurement
Measuring the AC component of an Output Voltage where both AC and DC voltage levels exist is sometimes necessary. This occurs primarily in amplifier circuits. The 270 has a 0.1 mfd, 400 volt capacitor in series with the OUTPUT jack.
The capacitor blocks the DC component of the current in the test circuit, but
allows the AC or desired component to pass on to the indicating instrument
circuit. The blocking capacitor may alter the AC response at low frequencies but
is usually ignored at audio frequencies (Figure 4-4).
+10
+8
PERCENT RELATIVE ERROR
a.
+6
OUTPUT RANGES
2.5 VAC RANGE
10VAC RANGE
50 VAC RANGE
250 VAC RANGE
+4
+2
0
-2
-4
-6
-8
-10
10Hz
100Hz
1KHz
10KHz
FREQUENCY
100KHz
1MHz
Figure 4-4. Frequency Response Output Ranges
Do not connect the OUTPUT jack to a circuit in which the DC voltage component
exceeds 350V.
Before proceeding with the following steps, review the Safety Precautions in
Paragraph 4.1.
a.
b.
c.
Set the function switch at AC (Figure 4-5).
Plug the black test lead into the - COMMON jack and the red test lead into the
OUTPUT jack.
Set the range switch at one of the range positions marked 2.5V, 10V, 50V, or
250V.
19
e.
f.
g.
Connect the test leads across the circuit voltage to be measured with the
black lead to the grounded side.
Turn on power.
For the 2.5V range, read the value
directly on the scale marked 2.5 VAC.
For the 10V, 50V, and 250V ranges,
read the red scale marked AC and
use the black figure immediately
above the scale. For the 500V range,
read the red scale marked AC and
use the 0-50 figures. Multiply the
reading by 10.
circuit power. When making measurements on the 50µA/250mV, 1 volt, or 10 amp
range, polarity can be corrected only by interchanging the test lead connector to
the current.
4.3
If the approximate voltage or current to be measured is known then the correct
range may easily be selected. However, particularly when working on faulty
equipment, the voltage or current is sometimes unknown or much higher than
normal and anticipated. When working on unfamiliar or unknown equipment,
always begin a measurement using the highest range available on the Instrument. Once it is determined that the voltage is within the limits of a lower range,
change to the lower range.
WARNING
READ MANUAL BEFORE USE
A.C.
Measurement Of Unknown Voltage Or Current
2.5V.
1V.
10V.
4.4
50V.
␮AMPS
250V.
!
Turn off power to the circuit and wait until
the meter indicates zero before disconnecting the test leads.
4.10 AC Voltage Measurement
0-1000V Range
1000V
270
1000V.
A.C.
D.C.
Test leads are provided with accessory screw-on alligator clips which may be
attached to the probe tips. Eliminating the need to hand-hold test prods to a
circuit for extended periods, the test clips also reduce hand proximity to a high
voltage circuit while energized. Circuit power must, of course, be turned off and
any charged capacitors discharged before connecting or disconnecting clips to
or from the circuit.
ALL TERMINALS IKV. MAX
Figure 4-3. Jacks and Switch
Positions for measuring AC
Voltages
4.5
!
Be sure that the range switch is set to the 500V/1000V range, function switch to
AC position, and test leads connected to common and 1000V jack.
Do not touch the Instrument or test leads while the power is on in the circuit being
measured.
d.
e.
f.
g.
4.6
DC Voltage Measurement 0-1V Range
a.
b.
c.
d.
e.
18
For polarity reversing see paragraph 4.2.
Before measuring voltage review the SAFETY PRECAUTIONS listed in paragraph 4.1. Also, when using the 270 as a millivoltmeter, care must be taken to
prevent damage to the indicating instrument from excessive voltage. Before
using the 250 millivolt range, use the 1.0-volt DC range to determine that the
voltage measured is not greater than 250 millivolts (or .25 volt DC).
a. Set the function switch at +DC (Figure 4-1).
b. Plug the black test lead in the - COMMON jack and the red test lead into the
+50 µA/250mV jack.
c. Set the range switch at 50 µA COMMON position with 50V.
d. Connect the black test lead to the negative side of the circuit being measured
and the red test lead to the positive side of the circuit.
e. Read the voltage on the black scale marked DC and use the figures marked
0-250. Read directly in millivolts.
Do not attempt any circuit-to-ground voltage measurement which may exceed
1000 volts.
Set the function switch at AC (Figure 4-3).
Set the range switch at 500/1000V position.
Plug the black test lead into the - COMMON jack and the red test lead in the
1000V jack.
Check that the power is off in the circuit being measured and that all its
capacitors have been discharged.
Connect the test leads across the circuit voltage to be measured with the
black lead to the grounded side, if any.
Turn on the power in the circuit being measured.
Read the voltage on the red scale marked AC. Use the 0-10 figures and
multiply by 100.
DC Voltage Measurement 0-250 mV Range
NOTE:
Use extreme care when working in high voltage circuits. Do not handle the
Instrument or test leads while the circuit being measured is energized. OBSERVE ALL SAFETY PRECAUTIONS in paragraph 4.1 and in the instruction
manual for the equipment being tested.
a.
b.
c.
Test Leads
500V.
COMMON
COMMON
Set the function switch at + DC (Figure 4-1).
Plug the black test lead into the - COMMON jack and the red test lead into the
+ 1V jack.
Set the range switch at 1V (COMMON position with 2.5V).
Connect the black test lead to the negative side of the circuit being measured
and the red test lead to the positive side of the circuit.
Read the voltage on the black scale marked DC and use the figures marked
15
0-10. Then divide the reading by 10.
4.7
DC Voltage Measurement 0-2.5 Through 0-500V Range.
a.
b.
c.
Set the function switch at + DC (Figure 4-1).
Plug the black test lead into the COMMON jack and the red test lead
into the + jack.
Set the range switch at one of the
five voltage range positions marked
2.5V, 10V, 50V, 250V or 500V.
When in doubt as to the voltage present,
always use the highest voltage range
as a protection to the Instrument. If the
voltage is within a lower range, the
switch may be set for the lower range to
obtain a more accurate reading.
IMPORTANT: Be sure power is off in the
circuit being measured and all capacitors discharged.
d.
e.
f.
f.
g.
charged.
Connect the black test lead to the negative side of the circuit being measured
and the red test lead to the positive side of the circuit.
Turn on power in circuit being measured.
Read the voltage using the 0-10 figures on the black scale marked DC.
Multiply the reading by 100.
!
Turn off power to the circuit and wait until the meter indicates zero before disconnecting the test leads.
4.9
AC Voltage Measurement 0-2.5 Through 0-500V
Range
WARNING
!
READ MANUAL BEFORE USE
+50 µAMPS.
250MV.
+1V.
+D.C.
-D.C.
2.5V.
1V
10V.
50V
µAMPS
250V.
500V
COMMON
1000V
270
1000V
AC. D.C
Connect the black test lead to the
negative side of the circuit being
Figure 4-1. Jacks and Switch
measured and the red test lead to
Positions for Measuring DC Voltages
the positive side of the circuit.
Turn on the power in the circuit being measured.
Read the voltage on the black scale marked DC. For the 2.5V range, use the
0-250 figures and divide by 100. For the 10V, 50V, and 250V ranges, read the
figures directly. For the 500V range, use the 0-50 figures and multiply by 10.
ALL TERMINALS 1KV. MAX.
Turn off power to the circuit and wait until the meter indicates zero before disconnecting the test leads.
4.8
e.
DC Voltage Measurement 0-1000V Range
Branch and distribution circuits (120/240/480V etc.) can deliver dangerous explosive power momentarily into a short circuit before the fuse/breaker opens the
circuit. Make sure that the Instrument switches are set correctly, jacks are properly connected, and that the circuit power is turned off before making connections
to such circuits.
The 270 responds to the average value
of an AC waveform. The Dial is calibrated in terms of the RMS value of a
pure sine wave. If the waveform is nonsinusoidal, and depending upon its
waveform, the reading may be either
higher or lower than the true RMS value
of the measured voltage. Thus an error
may be introduced if the 270 is used to
measure a non-sinusoidal waveform.
Also, accuracy is lessened at higher input frequencies (Figure 4-2).
Before proceeding with the following
steps, review the Safety Precautions in
Paragraph 4.1.
WARNING
READ MANUAL BEFORE USE
+50 µAMPS.
250MV.
+1V.
+D.C.
-D.C.
2.5V.
1V
10V.
50V
µAMPS
250V.
!
Use extreme care when working with high voltage circuits. Do not touch the
Instrument or test leads while power is on in the circuit being measured.
a.
d.
Set the function switch at + DC (Figure 4-1).
Set the range switch at 1000V (dual position with 500V).
Plug the black test lead into the - COMMON jack and the red test lead into the
1000V jack.
Be sure power is off in the circuit being measured and all capacitors dis-
16
Set the function switch at AC (Fig270
ure 4-3).
Set the range switch at one of the
Figure 4-2. Frequency Response,
five voltage range positions marked
AC Voltage Ranges
2.5V, 10V, 50V, 250V or 500V.
When in doubt as to actual voltage present, always use the highest voltage
range as a protection to the Instrument. If the voltage is within a lower range,
the switch may be set for the lower range to obtain a more accurate reading.
Plug the black test lead into the - COMMON jack and the red test lead into the
+ jack.
Turn off power to the circuit to be measured and discharge any capacitors.
COMMON
1000V
1000V
AC. D.C
ALL TERMINALS 1KV. MAX.
b.
Before proceeding with the following steps, review Safety Precautions in Paragraph 4.1.
a.
b.
c.
500V
c.
d.
17
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