Micronta 22-185A LCD Digital Multimeter owner`s manual

 Cat. No. 22-185A
OWNER'S MANUAL
"Please read before using this equipment
LCD
DIGITAL MULTIMETER
RADIO SHACK
A Division of Tandy Corporation
Fort Worth, Texas 76102
Printed in Taiwan
7A8 811018440E o MICRONTA®
EA
The MICRONTA? LCD Digital Multimeter is
a portable 3-2/3 digit, compact-sized
multimeter ideally suited for field, lab, shop,
bench and home applications. Here is a
review of some of the features that qualify
your new digital multimeter as real “pro”
e The latest IC and display technology is
used to achieve the lowest possible
component count. This, in turn, ensures
reliability, accuracy, stability and a really
rugged, easy-to-handle instrument. Two
analog-to-digital converters are used for
many special features.
Conveniently positioned range and
function switch knobs for one-hand
range function control.
Colored indication of the referential
ranges to the selected function.
Effective overload and transient
protection on all ranges except DC/AC
10A range.
Continuity function for quick continuity
check — buzzer sounds when circuit
resistance is approximately 300 ohms or
less.
©1988 Tandy Corporation
All Rights Reserved.
Micronta is a registered trademark of Tandy Corporation.
Diode check function lets you safely
check semiconductor junctions for open,
short or normal.
Over-range indication on each range.
Full auto-polarity operation.
Low battery voltage is automatically
detected and a caution is displayed.
Fold-out stand for bench-top use or for
hanging-up.
FEATURES ............ 0.0000... 2
SPECIFICATIONS ....................... 4
CONTROLS AND FUNCTIONS ......... 8
PREPARING FOR OPERATION ......... 12
CHECK BEFORE OPERATION .......... 16
MAKING MEASUREMENTS ........... 18
FUSE REPLACEMENT ............... 34
MAINTENANCE. ................e...... 36
A WORD ABOUT SAFETY ............. 38
SCHEMATIC DIAGRAM ............... 42
“ Warning: Use extreme caution in the use of this device. Improper
“use of this device can result in injury or death. Follow ali safeguards
suggested in this Owner's Manual in addition to normal safety pre-
cautions in dealing with electrical circuits. Do not use this device if
you are unfamiliar with electrical circuits and testing procedures.
Ranges & Accuracy
DC VOLTS
300 mV-3-30-300-3000 V
(Maximum Measurement
= 1000 Volts)
AC VOLTS
3-30-300-3000 V
(Maximum Measurement
= 750 Volts RMS)
at 50/60 Hz
45 Hz to 500 Hz
at 30 Volt Range
500 Hz to 10 kHz
at 30 Volt Range
+0.8% of reading and
+0.2% of full scale,
+1 in last digit
+1% of reading and
+0.5% of full scale,
+1 in last digit
+1.5% of reading and
+0.5% of full scale,
+1 in last digit
+10% of reading and
+0.5% of full scale,
+1 in last digit
Specifications
DC CURRENT
3-30-300 mA-30 A
(Maximum measurement = 10A)
AC CURRENT
3-30-300 mA-30 A
(Maximum measurement = 10A)
RESISTANCE
_ 300 ohm-3-30-300-3000 kohm
30 Megohm
+1.5% of reading and
+0.2% of full scale,
+1 in last digit
+1.5% of reading and
+0.5% of full scale,
+1 in last digit
+1.5% of reading and
+0.2% of full scale,
+1 in last digit
+5 digits maximum at
300 ohm range
+3% of reading and
+0.2% of full scale,
+1 in last digit
Specifications
Continuity Function:
Diode Check Function:
Input Impedance:
Range Selection:
Power Source:
Power Consumption:
Low Battery Indication:
Continuity buzzer sounds at less than 295 ohm {£20 ohm)
Input resistance.
Buzzer sounds 100 ms — 150 ms (typical) after input is
shorted.
For checking semiconductors open, short or normal.
10 Megohm (DCV/ACV).
More than 100 Megohm on 300 mV DC
Manual range
Four “AA” size 1.5V batteries, providing +3V
10 MW typical
“BATT” on the left of display indicates when + or —
supply is below 2.4V —2.6V.
Specifications
Polarity:
Overrange Indication:
Operating Temperature:
Storage Temperature:
Weight:
Size:
Accessories:
Automatic polarity
3000 with blinking "3".
When the measured value exceeds the maximum value, all
digits on display will blink.
32°F to 122°F (0°C to 50°C)
—4°F to 140°F (—20°C to 60°C)
11.6 ог. (3304)
6-3/4" X 3-1/16" X 1-1/4" (170 mm X 78 mm X 32 mm)
Fuse (0.5 A/250 V)
Banana type test leads (Cat. No. 278-704)
Controls and Functions
1. Digital display:
2. Power switch: Turns the meter ON and OFF. Set to (7 == 5
а. Low BATTery indicator — lights when batteries are CONTINUITY for continuity check. mm
sary ey ay my =! weak and need replacing. Tob
Sm | Li Li | ¡He b. AC indicator — lights when you select the AC 3. Range switch: Used for seiecting ranges: 15e
b ACT ALA IA, EAT d voltage/ current measurement. Voltage: DC V 300mV, 3V, 30V, 300V, 3000V =
Da c. Measured input values — shows the measured (Maximum measurable voltage is
value with decimal point and minus polarity indication 1000V.)
(2999 maximum.) ACV 3V, 30V, 300V, 3000V (Maximum
d. Measuring unit indicators — lights to show the measurable voltage is 750V.)
current measuring unit. Current: 3mA, 30mA, 300mA, 10A
e. Diode check indicator — lights in the diode check Resistance: 3000hm, 3kohm, 30kohm, 300kohm,
mode. 3000kohm, 30 Mohm
f. Continuity indicator — lights during the | Diode Check
CONTINUITY check mode.
| 4. Function switch: Used for selecting functions: DC V,
| АС V, Diode CHECK, kohm, DCmA and ACmA.
Controls and Functions
BEL rar
AC/DC — сом
UNFUSED
'0А + 100
2050 +0
5. Input (10A) jack: Connect (+) red lead for current
measurement with the 10A setting of the range switch.
6. Input (—) jack: Connect (—) black lead for all
measurements.
7. Input (+) jack: Connect (+) red lead here for all
measurements except 10 A range.
8. Battery/fuse Compartment : Open to
install/ replace fuse and/or batteries.
9. Fold-out Stand: Use to support the multimeter at
a convenient viewing angle for benchtop use or to
hang it up.
10
Controls and Functions
Special Panel Markings
AC/DC
AMPS
ONLY
10A MAX
UNFUSED
750V
MAX
©
A
1000V DC
750V AC
300mA
MAX
1
Special markings has been added to the panel to remind you of the
measurement limitations and safety.
The maximum current that can be measured is DC/AC 10A.
10A range is not fuse-protected.
To avoid electrical shock and/or instrument damage, do not connect
the common input terminal (-jack) to any source of more than 750V
with respect to earth/ground.
Refer to complete operatng instructions.
The maximum voltage that can be measured is 1000V DC or 750V
AC. The maximum current measurement at this terminal is
300 mA.
Be extra careful when making measurements for high voltage;
. DO NOT TOUCH TERMINALS OR PROBE ENDS.
Installing Batteries Preparing For Operation
All you need to do is load four 1.5V “AA” batteries. When the batteries become weak, “BATT” will be
We recommend that you use the alkaline type — such as displayed on the left part of the display. Replace all the BATT
our 23-552. batteries. NEVER LEAVE WEAK OR DEAD BATTERIES
IN YOUR UNIT. Even “leak-proof” types can leak and
i ; 30 300 3000
1. Be sure POWER is OFF and test leads are cause damage to the circuitry.
disconnected. | NOT IN USE
When you are not going to use your unit for a few RP
2. Push the arrow on the battery/fuse compartment weeks, remove the batteries.
cover and press in the direction of the arrow.
3. Snap the batteries in place — watch polarity!
4. Press the cover back into place.
Na A
12
Preparing For Operation
Using Test Leads
Test Leads
(Cat. No. 278-704)
Use only the same type of the test leads as are supplied
with your unit. These test leads are rated for 1200 volts;
replacements are available from your local Radio Shack
store (Radio Shack Cat. No. 278-704).
Caution: Although these test leads are rated for 1200
volts, the maximum rating of this meter is 1000 volts
DC/750 volts AC. You should not attempt to measure
any voltage more than 1000 volts DC/750 volts AC. Use
extreme care when using these high voltage ranges.
Using Stand
The fold-out stand allows you to use your unit on the
benchtop or hang from a hook.
14
Preparing For Operation
Top | _Fold-out
Stand
|
Bottom
Wall
Note: To fold the stand upwards fromthe middie position, press at the lower parts on both sides
slightly, then turn upwards. The stand can be removed by pressing the lower parts strongly.
Stand Positions and Their Usage
15
Check Before Operation
1. Set the power switch to ON. All the elements of the Functions Range Display Functions Range Display
display will appear on the LCD briefly as a self test. The K Ohm 30 Megohm | dd.dd MQ ОСТА 10 A dd dd A
display will soon revert to normal. 3000 kohm | dddd kQ ACMA 300 mA ddd.d mA
300 kohm ddd.d k0 30 mA dd.dd mA
2. Set the function switch to kO. 30 kohm | dd.dd k0 3 MA d.ddd mA
3 kohm d.ddd k(?
3. Rotate the range switch, starting at the top (30 300 ohm ddd.d £ Continuity Freon ddd.d Y
MO). The decimal point in the display should be DCV/ACV 3000 V dddd V
positioned as described in the chart on next page: 300 V ddd.d V Diode Check 3.000 d.ddd
7 30 V dd.dd V (Fixed range)
ЗУ d.ddd V
Notes: DEV only ) | 999.9 т\
1. In low voltage ranges, with leads unconnected to :
any circuit, the display may show some “phantom” 2. See the measuring unit on the display to distinguish
readings. This is normal and is caused by the high the range when two ranges have a decimal in the same
sensitivity and high input impedance of the meter’s position. For example, on the 300 mV range the unit | - I ri I. | - r I 7 ,
circuitry. As soon as a circuit is connected, normal display is “mV” against “V” on the 300 V range. Ce ee osos
accurate measurements are performed.
DC/AC Voltage Measurements
Making Measurements
Important: The maximum input limit for voltage
measurement is 1000 V/DC and 750 V/AC (RMS). If
you attempt to measure DC voltages above 1000 voits or
AC volts above 750 volts RMS, your unit may be
damaged. All the figures on the display will blink when
more than the maximum rate (DC 1000 V/AC 750 V) is
supplied: DISCONNECT PROBES IMMEDIATELY.
1. Set the function switch to DC V or AC V.
2. Set the range switch as required for the voltage level
to be measured. If you do not know the voltage level,
start with the range switch set to the highest position
and reduce the setting as required to obtain a
satisfactory reading.
3. Plug the red lead into the + jack and the black lead
into the — COM jack.
4. Connect the probes to the circuit to be tested. In DCV,
the minus sign will appear if voltage is negative.
5. Read the range by the position of the decimal point.
AC/
AMP
ONLY
DC
5
UNFUSE
{OA
IDA MAX
> ©
PARALLEL
©
|
= Red Lead +
Black Lead —
CONNECTION
18
19
Making Measurements
|
|
Making Measurements
Tala
LILLO Y
(rit
{LA
2 оо
1171
Ea LIL
3 30 300 3000
Notes:
1. On 300 V and 300 mV ranges, the decimal point will
appear in the same position {one place to the left), but if
the 300 mV range is selected, “mV” will appear on the
display.
2. If the function switch is rapidly shifted from Kohm to -
DCV with the range switch set to the 300 mV position,
the display might show the over-range indication
because of the high input impedance. Short the test
leads to remove this condition.
3. When measuring DCV or ACV with no circuit under
test the display may show small changes in the lower
ranges. This is normal. A high input impedance produces
this “wandering” effect. As soon as a circuit Is
connected, normal accurate measurement is performed.
HINTS: When you are using the meter to probe for a
voltage in a high voltage circuit, we recommend that you
do not try to position both of the probes at once. Instead,
you should clamp one of the leads to the neutral or
ground lead of the circuit (usually a bare, green or white
lead, in AC wiring circuits) using our insulated Slip-On
Alligator Clips (Cat. No. 270-354), and then probe for
voltages with the other probe. This helps to prevent you
from accidentally touching a “hot” wire, since you need
only concentrate on one test probe. Never clamp on to a
“hot” wire, (usually red, black or blue, in AC wiring
circuits), since if you did so and then touched the other
probe connected to the meter, you could receive an
electric shock.
Neutral
or
Ground
Wire
Black Lead —
Test Unit
Red Lead
20
21
Making Measurements
AC Voltage Riding on a DC Source Bias Measurement
AC Voltage
dee Nee fe NF DC bias
You can measure an AC voltage superimposed on a DC
voltage source bias. Set the function switch to ACV.
However, NEVER ATTEMPT TO MEASURE ANY CIRCUIT
OVER 750V AC with respect to earth ground.
Measuring 3-Phase AC Voltages
Making Measurements
22
This meter is designed primarily to measure household
AC voltages. When measuring 3-phase circuits line-to-
line, the value of the voltage will actually be higher than
the rated line-to-ground 3-phase voltage. It is important
that you do not exceed the maximum RMS AC rating of
this meter, which is 750V AC. To determine the highest
possible voltage on a 3-phase line, multiply the stated
voltage by the square root of three (approximately 1.75).
Severe damage as well as a dangerous shock hazard could
result if the meter is connected to a circuit that exceeds
the voltage rating of the meter.
23
Making Measurements
DC/AC Current Measurements
To measure current, you must break the circuit and
connect the leads to two circuit connection points. Never
connect the leads across a voltage source; doing so
will blow the fuse or damage the circuit under test. The
maximum input limit for DC current/AC current
measurement is 10A (with red lead plugged to 10A jack).
1. Set the function switch to DCmA or ACmA.
2. Set the range switch to the desired position.
Making Measurements
24
3. For 300 mA max., plug the red lead into the + jack,
and the black lead into the — COM jack.
For 10A max., plug the red lead into the 10A jack, and
the black lead into the — COM jack.
4. Remove power from the circuit under test and then
break the circuit at the appropriate point.
(300 mA Measurement)
AC/DC 104A — COM
ons 750V
MAX
UNFUSEO O
Black Red
Lead Lead
(10A Measurement) y
ACrOC IOA — COM
8 (A) te
Mm
IOA MAX ( MAX
+ 1000v DC
7
Y
50V AC
A (О) 300mA
MAX
UNFUSED ©
Red Lead Black Lead
Q
—
o
25
Making Measurements Resistance Measurements Making Measurements
5,6 5. Connect probes to the circuit in series. Note: The resistance measuring circuit compares the 1
voltage which is gained through a known resistance
6. Apply power and read current. | (internal) with the voltage developed across the unknown
resistance. Thus when checking “in-circuit” resistance,
7. If the polarity of the current being measured is be sure the circuit under test has all power removed (are
negative in DC measurement, the value displayed will be | all capacitors fully discharged?).
preceded by a minus (>) sign (Figure (a)). Input of more 2
Ni than the maximum rate (DC/AC 10A) will cause the 1. Set the function switch to the k{} position.
Power Supply Eula GE display to blink on and off as a warning (Figure (b)).
(a) (b) 2. Set the range switch to the desired position.
E TSE 4080
Lead Wire 3. Plug the red test lead into the + jack and the black 3 LE
Test Unit lead into the — COM jack. E (0) 1 A (Qe
Note: All current ranges except the 10A are fuse- | prise ~~" © —)
SERIES CONNECTION protected. If inoperative, check the fuse. Black Lead Red Lead
26 27
Making Measurements
Making Measurements
4
O
Black Lead Red Lead
Resistor
PARALLEL CONNECTION
4. Connect the probes across the circuit to be
measured.
5. For resistances of approximately 1 megohm and
above, the display may take a few seconds to stabilize.
This is normal for high resistance readings.
Use the measuring unit display to see the range you
are in. “Q” or “k{}" to distinguish between 300 ohm
and 300 kohm, “MQ” or “k0Q0” for 30 Megohms vs.
30 kohms.
Notes:
1. Your unit has a circuit to protect the resistance
ranges from over-voltage (500V AC 1 minute). To prevent
accidentally exceeding the rating of the protection circuit
and to ensure the correct measurement, never connect
the probes to a source of voltage when the function
switch is set to the K or diode check position.
2. Some devices could be damaged by the
current applied during resistance
measurements. The table below lists the
voltage and current available for each
3. When you short the test leads in the
300 ohm range, a small value (no more
than 0.3 ohms) will be displayed. This is
due to internal circuit and test leads
range. resistance. You may need to take note of
this value and deduct it from the measured
value when you measure very small
resistances.
Range A B C
* A is the open circuit voltage at the jacks in
300 ohm | 3.0V | 180 MY | 700 uA volts.
ЗК 1.3V | 310 mV | 140 MA | + Bisthe voltage across a resistance equal
30 k 1.3V | 400 mV 20 pA to full scale value.
300 k 1.3V | 460 mV 2 MA x C is the current through a short circuit at
3000 k 0.7V | 440 mV | 0.4 HA the input jacks. All values are typical.
30M 0.7V | 440 mV | 0.04 LA
28
29
Making Measurements
Continuity Function
OFF ON CONTINUITY
=
— COM
MES
ONLY Toy
10A “©
UNFUSED
Black Lead Red Lead
This tester has a built-in audible continuity function.
1. Set the power switch to the CONTINUITY position.
2. Set the function switch to KO.
The range is automatically set to 320 ohm.
3. Connect the red lead into the + jack and the black
lead into the — COM jack.
Making Measurements
4. Connect the probes to the circuit you want to check.
5. If the circuit resistance is 300 ohms or less, the
buzzer will sound.
Note: When the switch is in the CONTINUITY position,
the buzzer will also sound when:
1. the function or range switch setting is changed.
2. over-range takes place (except in kohm and diode
check functions).
Nomis | PARALLEL
E CONNECTION
Red
Lead
| 7)
OFF ON CONTINUITY
7
Tm ws J]
30
31
Making Measurements
Diode Check
Making Measurements
AMPS
ONLY SOV
HOA MAX MAX
UNFUSED O
BI ack
Lead
3 ——>——
oe
Red
Lead
1. Set the function switch to the diode check position.
The range is automatically set to 3V.
2. Plug the red test lead into the + jack and the black
lead into the — COM jack.
3. Remove power from the circuit under test.
4. Connect the probe to the semiconductor device you
want to check and note the meter reading.
5. Reverse the probes and note the second reading. If
the first reading shows some value and second is
overrange, the device is good. If both are overrange, the
device is open. If the reading are both very small or zero,
the device is shorted.
Note: The values indicated on the display during the
diode check operation shows the actual forward voltage
(max. 2V). If the value 1s around 0.400 the device is
germanium type: if it is around 0.600 the device is
silicon type. An LED will make the meter display a value
of about 1.800.
PARALLEL
CONNECTION
æ 5
Lead Lead
Cathode
Mark — —H—M
32
33
FUSE REPLACEMENT на
1 OFF ON CONTINUITY
WARNING: TO AVOID ELECTRIC SHOCK,
DISCONNECT THE TEST PROBES BEFORE REMOVING
BATTERIES OR FUSE. REPLACE ONLY WITH SAME
TYPE OF BATTERIES OR FUSE. THIS INSTRUMENT
CONTAINS NO USER SERVICEABLE PARTS. SERVICE
SHOULD BE PERFORMED ONLY BY QUALIFIED
PERSONNEL.
CAUTION: FOR CONTINUED PROTECTION AGAINST
FIRE, REPLACE ONLY WITH 0.5A, 250V FUSES (Cat. No.
270-1241).
1. Be sure POWER is OFF and test leads are
disconnected.
2. Open the battery/fuse compartment cover.
3. Pull the red ribbon in the fuse compartment; the fuse
will pop out.
Fuse replacement
34
Note: The fuse in your digital multimeter is a special
size and type. One spare fuse comes supplied with your
unit.
4. Insert a new fuse on the ribbon ring. Use only a fuse
of the same type/rating (0.5A, 250V, 5 X 20 mm
miniature fuse; Radio Shack Cat. No. 270-1241).
5. Install the new fuse with ribbon in the fuse
compartment.
6. Close the battery/fuse compartment cover.
WARNING: DO NOT OPERATE YOUR UNIT UNTIL THE
BATTERY/FUSE COVER IS IN PLACE AND FULLY
CLOSED.
Fuse
(Cat.
BR
No. 270-1241)
0
35
Your MICRONTA LCD DIGITAL MULTIMETER is an
example of superior design and craftmanship, and
should be treated with care. The suggestions below will
help you enjoy this product for many years.
Keep it dry. If water should get on it, wipe it off. Water
contains minerals that can corrode electronic circuits.
Do not store in hot areas. High temperatures can
shorten the life of electronic devices, damage batteries,
and warp or melt certain plastics.
Do not drop it. This might cause permanent damage.
The circuit boards and case can be broken.
Maintenance
Do not use or store it in dusty, dirty areas. This will
cause premature wear of moving parts.
Do not use harsh chemicals, cleaning solvents, or
strong detergents to clean it. Wipe it with a soft cloth
dampened in a mild soap-and-water solution.
Be sure batteries are the correct type—do not use
general purpose batteries if alkaline batteries are
recommended. Remove old, weak batteries—they can
leak chemicals that damage electronic circuits.
If the unit is not working properly, take it to your local
Radio Shack. The personnel there will assist you and, if
necessary, arrange service.
36
37
A Word About Safety
2
N
yu
o>
>
ABOVE 100V
Every precaution has been taken in the design of your
meter to ensure that it is as safe as we can make it.
However, safe operation depends on you, the operator.
We recommend that you follow these simple safety
rules:
1. Never apply voltages to the meter that exceed the
limits given in the specifications. Never apply more than
1000V DC or 750V RMS AC between input jacks and/or
ground.
2. Use extreme caution when working with voltages
above 100V. Always disconnect power from the circuit
being measured before connecting test leads to high-
voltage points.
—
3. Never connect to a source of voltage when the KQ or
diode check function 1s selected.
— COM
38
Eo 750v A SE
00.05
4. Always discharge filter capacitors before attaching
test leads to a power supply.
DISCHARGE /
39
A Word About Safety
A Word About Safety
5 OFF ON CONTINUITY
0A MAX
UNFUSED ©
5, Battery and/or fuse replacements should only be
performed after the test leads have been disconnected
and POWER is OFF.
6. Never operate unless the battery cover is in place and
fully closed.
7. Since many AC-DC sets have a potentially “hot”
chassis, be sure that the top of your workbench and the
floor underneath it are made of non-conductive
materials.
The MICRONTA digital multimeter comes to you fully
calibrated and tested. Under normal use, no further
adjustment should be necessary. In case the meter
should require repair, do NOT try to adjust yourself; bring
it to your nearest Radio Shack store. SERVICE BY
UNAUTHORIZED PERSONNEL WILL VOID THE
WARRANTY.
Non-conductive
Non-conductive
40
41
Ey y Ce
x d.C. Ci, a
zÉ
2a03vBhERE id
vio, 02
РТ Тян ©
RADIO SHACK LIMITED WARRANTY
This product is warranted against defects for 90 days from date of purchase from Radio
Shack company-owned stores and authorized Radio Shack franchisees and dealers.
Within this period, we will repair it without charge for parts and labor. Simply bring your
woos Radio Shack sales slip as proof of purchase date to any Radio Shack store. Warranty
does not cover transportation costs. Nor does it cover a product subjected to misuse or
accidental damage.
EXCEPT AS PROVIDED HEREIN, RADIO SHACK MAKES NO WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING WARRANTIES OF MERCHANTABILITY AND
В 5 FITNESS FOR A PARTICULAR PURPOSE. Some states do not permit limitation or
mo exclusion of implied warranties; therefore, the aforesaid limitation(s) or exclusion(s) may
not apply to the purchaser.
This warranty gives you specific legal rights and you may also have other rights which vary from state to state.
SMC 4301 F CA
IC 1
ZEHN
03-08
. a e We Service What We Sell
NOTES: (1) ALL RESISTANCE VALUES ARE IN OM [K=10"CHM Melo” CHO
(2) ALL CAPACITANCE VALUES ARE IN AF [P-10%F)
(5) SWITCHES.
Sa POWER SW WITH CONTIMUITY (SLIDE)
SW2: RANGE SW (ROTARY)
SW FUNCTION Sw (ROTARY)
42