Radio Shack 22-168A User manual

: MANUAL DUAL-DISPLAY
OWNER’S MANUAL DIGITAL MULTIMETER
w/PC Interface
Please read before using this equipment.
Cat. No. 22- 168A,
8 zy, =< y)
Sy a £———
(U1) Radio Shaek
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INTRODUCTION
Your Radio Shack LCD Digital Multimeter is a
portable, 3% digit, compact test instrument ideally
Suited for use in the field, lab, shop, and home.
Here are some of the professional features of
your new digital meter.
Computer Interface and Software — includes
both MS-DOS and Microsoft Windows software
-to let you interface the meter with your PC-com-
patible computer to log and graph measure-
ments.
Memory Recording — stores ten measure-
ments which you can download to a computer.
Frequency Check Function — measures fre-
quencies up to 20 MHz.
Transistor-Check Function — measures the
gain (hFE) of small-signal, bipolar transistors.
Capacitor-Check Function — measures the
capacitance of low-voltage capacitors.
Dual-Measurement Function — shows both
the AC voltage and frequency for AC measure-
ments or the logic level and ripple frequency for
logic measurements.
Analog Bargraph Display — indicates the mag-
nitude of the input compared to the full-scale
value of the measurement range.
MAX/MIN Hold Function — displays the maxi-
mum or minimum measured value on the second-
ary display.
Data Hold Function — freezes the secondary
display so you can keep the measured value
there even after you disconnect the probes.
Relative Offset — stores a value in memory and
displays the difference between the stored value
and subsequent readings.
© 1994 Tandy Corporation.
‘All Rights Reserved.
Radio Shack is a registered trademark used by Tandy Corporation.
2 Windows Is a trademark and MS-DOS Is a registered trademark of Microsoft Corporation.

Continuity Function — makes it easy to check
fuses, alarm wiring, cables, and connections.
Auto-Polarity Operation — protects ‘your meter
and gives valid measurements when you connect
the leads in reverse polarity.
Diode-Check Function — safely checks semi-
conductor junctions for open, short, or normal.
Combined (Function and Range) Selector
Switch — makes the meter easy to use.
Latest IC and Display Technology — ensures
reliability, accuracy, stability, and ease of opera-
tion.
Auto Power Shut-Off — tums off after 10 min-
utes of non-use to help conserve battery power.
Beeper — sounds tones for overload warming,
continuity function, and range selection.
Logic Test Function — checks logic levels
without extra logic probes.
Overload and Transient Protection — helps
protect the meter from accidental overload on
most ranges.
Low-Battery Indicator — appears when you
need to replace the batteries.
UL Listed — passes the stringent tests required
by Underwriters Laboratories for safety.
Cautions:
© Completely read this manual before you use
the meter.
¢ If you are not familiar with meters and testing
procedures, we suggest you read “Using
Your Meter” (Radio Shack Cat. No. 62-2039).

CONTENTS
A Word About Safety oo.
Specifications %
Special Panel Markings .
Preparation ......
Installing/Replacing the Battery
Using the Test Probes
Using the Stand...
Propping Up the Meter
Hanging the Meter
Pre-Operation Check
Making Measurements
Understanding Phantom Readings |
Measuring High-Voltage Circuits
AC/DC Voltage Measurement ..... ¥
Measuring an AC Voltage on a DC Bias 5
Measuring 3-Phase AC Voltages ..
Measuring AC/DC Current
Measuring Capacitance
Measuring Resistance
Checking Diodes
Checking Continuity

Checking Transistors.
Measuring Frequency.
Logic Test.
Using the Advanced Functions
Using the Auto-Hold Feature
Using the Data Hold Feature
Using the Minimum Feature
Using the Maximum Feature
Using the Relative Measurement Feature
Using the Communication Feature.......
Storing Measurements in Memory .
Recalling Stored Measurements
Using the Comparison Measurement Feature
Using the Dual Measurements Feature........
Using the Meter with a Computer-.......
Interfacing the Meter with a Compute:
Using the Supplied Software
Technical Information........
Communication Parameters
Data Format............0.00
Hints for Writing Your Own Software.
Replacing the Fuse............0::0ccse
Care and maintenance
FCC Statement.......

A WORD ABOUT SAFETY
This meter has been manufactured and tested
in accordance with IEC 348 and DINS7411/VDE
0411 Part 1 : Safety Requirements for Electronic
Measuring Apparatus, Safety Class II.
We have taken every precaution in designing and
manufacturing this meter to ensure that it is as
safe as we can make it. But safe operation de-
pends on you, the operator. We recommend that
you follow these simple safety rules:
Never apply voltages to the meter that exceed
the limits given in the specifications. Never
apply more than 1000 V DC or 750 V AC bet-
ween any terminals or between any input jack
and ground.
© Use extreme caution when working with volt-
ages above 30 V AC or 60 V DC. Always dis-
connect power from the circuit you are mea-
suring before you connect the test probes to
high-voltage points.
e Never connect the test probes to a source
of voltage when you select diode, resistance,
continuity, current measurement, capacitance,
or hFE functions.
© Always tum off the meter’s power and
disconnect the test probes before you replace
the battery or fuse.
© Never operate the meter unless the back cov-
er is in place and fully closed.
¢ Because some AC/DC sets have a hot chas-
sis, be sure the top of your work bench and
the floor undemeath it are made of noncon-
ductive materials.
The meter is fully calibrated and tested. Under
normal use, no further adjustment should be ne-
cessary. If the meter should require repair, do
not try to adjust it yourself. Take it to your local
Radio Shack store. Service by unauthorized per-
sonnel voids the warranty.

WARNING: USE EXTREME CAUTION IN THE
USE OF THIS DEVICE. IMPROPER USE OF
THIS DEVICE CAN RESULT IN INJURY OR
DEATH. FOLLOW ALL SAFEGUARDS SUG-
GESTED IN THIS OWNER’S MANUAL IN ADDI-
TION TO NORMAL SAFETY PRECAUTIONS IN
DEALING WITH ELECTRICAL CIRCUITS. DO
NOT USE THIS DEVICE IF YOU ARE UNFA-
MILIAR WITH ELECTRICAL CIRCUITS AND
TESTING PROCEDURES.
NOT FOR COMMERCIAL OR INDUSTRIAL
USE.

SPECIFICATIONS
DC VOLTS (Maximum Measuremen
200 mV - 2 - 20- 200 - 1000V .....
= 1000V)
auaantbdasasiis -- + 0.8% of Reading and
+ 0.3% of Full Scale
+1 in Last Digit
AC VOLTS (Maximum Measurement = 750 V)
200 mV - 2- 20-200V . aejainnisses -- + 1.2% of Reading and
+ 0.8% of Full Scale
+3 in Last Digit
TSO N ittcitesisisinssantivartictns ta aieaebiskacinineniaiiacanitiinsiabicuinsndiinttiienstutcn te TOI65OF ROAGING ANd
+ 1.2% of Full Scale
+3 in Last Digit
DC CURRENT vena Measurement = ae
200
uA-2mA
.
sada
ssrnanssaniennsieunarunannannemennenenanae
1.0%
of
Reading
and
+0.5% of Full Scale
+1 in Last Digit
+1.5% of Reading and
+ 1.2% of Full Scale
+1 in Last Digit
Q0A ores puna gunner setiineinnnnnnes + 2.5% Of Reading and
+ 2.0% of Full Scale
+5 in Last Digit
20 MA ~ 200 MA essssssssssssssssesesnnssennnseeee

RE
AC CURRENT (Maximum Measurement = 20 A)
200 uA-2mA....... + 1.5% of Reading and
+ 1.0% of Full Scale
+3 in Last Digit
20 mA- 200 mA .. + 2.3% of Reading and
+ 1.8% of Full Scale
+5 in Last Digit
20A... .. +3,.5% of Reading and
+3.0% of Full Scale
+7 in Last Digit
CAPACITANCE
200 pF - 200 nF ........ .. + 2.5% of Reading and
+ 2.0% of Full Scale
+3 in Last Digit
20 uF - 200 HF ...... .. £ 4.5% of Reading and
+4.0% of Full Scale
+5 in Last Digit
RESISTANCE
200 Ohm. ....... sue £1% Of Reading and
+ 0.5% of Full Scale
+3 in Last Digit

2 koh - 20k - 200K = 2 MOWM «.-sssressssseesseeseen
1% of Reading and
+0.5% of Full Scale
+1 in Last Digit
QO MOB on ssccssesssssessesessee .. £ 1.5% of Reading. and
+ 1.0% of Full Scale
+2 in Last Digit
2000 MOh .....scsscssssssssessseseeee .. + 5.5% of Reading and
+ 5.0% of Full Scale
+5 in Last Digit
FREQUENCY
QHZ = ZO MZ ansscssssssseesensinennosesessseteon + 2.5% of Reading and
+ 2.0% of Full Scale
+3 in Last Digit
DIODE CHECK FUNCTION ...................... For checking semiconductors for open, short, or normal
CONTINUITY TEST . Continuity buzzer sounds at less than 40 ohms
FE MEASUREMENT ........00.....cccesccssssseessns O-1000 HFE values for either PNP or NPN transistor.
Base DC Current about 10 yA
Vce about 3.0V
10

SNe EEE!
COMMUNICATION ........:cccccssssssseesnsenneeeneen .... Transmission Rate: 1200 baud
Character Coding: 7-Bit ASCII
Parity Bit: None
Stop Bit: 2
RS-232 Serial Interface
INPUT IMPEDANCE ............:cscsssscsssssssseesunsnimssennsaeesuseseiusstouseenaneeenneeeennee 10 Mohm (DCV/ACV all ranges)
RANGE SELECTION ................ inctnantoty 1 oe sss Manual (rotary-type switch)
POWER SOURCE ou... sussussses 9 V battery (such as Radio Shack Cat. No. 23-553,
not supplied)
POWER CONSUMPTION .........::cccccsssssssssssssssessesensesseeeeeenennee .. 70 mW typical
LOW BATTERY INDICATION ..........00000:00.A battery symbol on the right of the display indicates
when battery voltage drops below 6.5V-7.5V
POLARITY sssceesssssessesseenseesetneeene ...... Automatic polarity selection
OVERRANGE INDICATION ............... OL appears, and the bargraph flashes
"1

a
OPERATING TEMPERATURE ...... 32 to 104°F (0 to 40°C)
STORAGE TEMPERATURE ..... swe 14 to 122°F(—10 to 50°C)
WEIGHT ........ . 12.35 0z (350 grams)
SIZE ...... vue TUX BUX 1%6 Inches (187 X87 X34 mm) (HWD)
ACCESSORIES (included) ... Fuse 2A/250V (Fast-Acting Type)
Shrouded Banana-Type Probes
RS-232C Cable, 3'/-Inch Disk

SPECIAL PANEL MARKINGS
We have placed the following special markings
‘on the panel to remind you of the measurement
limitations and safety.
20A MAX The maximum current that you can
FUSED measure at this terminal is 20 amps
DC/AC. This terminal.is fuse protec-
ted. For your safety during continuous
measurements, keep the duty cycle
as 30 seconds in use and 15 minutes
in rest.
200mA The maximum current that you can
MAX measure at this terminal is 200 mA
FUSED DC/AC. This terminal is limited to 2
amps by a fuse.
500V MAX To avoid electrical shock or instru-
4. ment damage, do not connect the
‘= common input terminal (COM) to
any source of more than 500 V with
respect to earth/ground.
MAX
The maximum voltage this meter can
750V AC measure is 1000V DC or 750V
1000V DC ac.
4
A
Be extra careful when making high-
voltage measurements. DO NOT
TOUCH THE TERMINALS OR
PROBE ENDS.
Refer to the complete operating in-
structions.
13

PREPARATION
INSTALLING/REPLACING THE
BATTERY
Your meter requires a 9V battery (not supplied)
for power. For reliable operation, we recommend
an alkaline battery, such as Radio Shack Cat.
No. 23-553.
Warning: TO AVOID ELECTRIC SHOCK, DIS-
CONNECT BOTH LEADS FROM ANY EQUIP-
MENT BEFORE YOU REMOVE OR INSTALL
THE BATTERY.
Follow these steps to install the battery:
1. Tum off power and disconnect the two test
probes.
2. Loosen the battery compartment cover screw
and slide off the cover. Remove the old battery,
if necessary.
Qe
)
3. Place the battery into the supplied insulation
capsule and snap it onto the contacts.
S=
(4
———
Warning: Do not discard .the provided bat-
tery insulation capsule. If you do not use
this insulation capsule properly, damage or
injury might result.
4. Replace the battery compartment cover and
secure it with the screw.

WARNING: DO NOT OPERATE THE METER
UNTIL YOU REPLACE THE BATTERY AND
CLOSE THE BATTERY COMPARTMENT
COVER.
Notes:
¢ When the battery indicator appears, replace
the battery.
* Never leave a weak or dead battery in your
meter. Even a leakproof battery can leak
damaging chemicals. When you are not
going to use your meter for a week or more,
remove the battery.
USING THE TEST PROBES
Use only the type of test probes supplied with
your meter. These test probes are rated for 1200
volts. You can purchase replacement probes
from your local Radio Shack store.
Cautions:
* Although the test probes are rated for 1200
volts, the maximum rating of your meter is
1000 volts DC and 750 volts AC. If you try
to measure DC voltages above 1000 volts
or AC voltages above 750 volts, you might
damage your meter and expose yourself to
a serious shock hazard. Use extreme care
when you measure high voltages.
* Never connect the probe you plug into the
COM terminal to a source of voltage greater
than’ 500 volts with respect to earth ground.
This creates a serious shock hazard.

USING THE STAND
Use your meter s stand to prop up or hang the
meter.
Propping Up the Meter
If you prop up your meter on a benchtop, the
stand helps provide a better viewing angle. To
use the stand as a prop, just open it away from
the meter and set it on a flat surface.
16
Hanging the Meter
To hang the meter, remove the stand by
pressing the lower parts of the stand together.
Then insert the stand into the top two holes as

PRE-OPERATION CHECK
To ensure correct operation and familiarize your-
self with the meter, follow these steps before you
use it.
1. Press POWER to turn on the meter. The meter
beeps once.
2. Plug the black probe into the meter’s COM
terminal and the red probe into the meter’s
V/Q. terminal.
3. Rotate the function selector to 4. Your meter
displays OL and the analog bargraph flashes.
4. Touch the probe tips together. Your meter
sounds a tone.
5. Rotate the function selector to one of the other
OHM positions. Your meter displays a value
of less than 1 ohm when you touch the probe
tips together.

MAKING MEASUREMENTS
UNDERSTANDING
PHANTOM READINGS
In some DC and AC voltage ranges, when the
probes are not connected to any circuit, the
display might show a phantom reading. This is
normal. The meter’s high input sensitivity pro-
duces a wandering effect. When you connect the
probes to a circuit, accurate readings appear.
MEASURING
HIGH-VOLTAGE CIRCUITS
When you use the meter to check a high-voltage
Circuit, do not try to position both probes at once.
Instead, clamp one’probe to the neutral or ground
lead of the circuit (usually a bare, green, or white
wire in AC wiring circuits) using insulated Slip-
On Alligator Clips (Cat. No. 270-354). Then probe
for voltages with the other probe. This helps pre-
vent you from accidentally touching a hot wire
because you need to concentrate on only one
test probe.
18
Warning: Never clamp onto a hot wire, (usually
red, black, or blue in AC wiring circuits.) If you
clamp onto a hot wire and touch the other probe,
you could receive a shock.

AC/DC VOLTAGE MEASUREMENT
WARNING: DO NOT TRY TO MEASURE A
VOLTAGE GREATER THAN 1000 VOLTS DC
OR 750 VOLTS AC. YOU MIGHT DAMAGE
YOUR METER AND EXPOSE YOURSELF TO
A SEVERE SHOCK HAZARD.
Note: All the figures on the display blink when
more than the maximum voltage (DC 1000/AC
750 VOLTS) is supplied. If this happens,
DISCONNECT THE PROBES IMMEDIATELY.
Follow these steps to measure AC/DC voltage.
1. Rotate the function selector to the desired po-
sition.
Select the range 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 voltage position and reduce the
setting as needed to get a reading.
. Press DC/AC to toggle between DC and AC
voltage. AC appears for AC measurements.
. Plug the black probe into the meter's COM
terminal and the red probe into the V/N. termi-
nal.
. Connect the probes to the AC/DC voltage
source you want to measure.

© If polarity is negative, — appears on the left
of display.
¢ For the most accurate measurement, select
the lowest possible voltage range without
getting an overload reading.
Measuring an AC Voltage
on a DC Bias
To measure an AC voltage superimposed on a
DC voltage source bias, follow the steps for mea-
suring AC voltage.
Caution: Never try to measure an AC voltage
that is riding on a DC voltage level where the
peak AC voltage exceeds 1000V with respect
to earth ground.
MEASURING 3-PHASE AC
VOLTAGES
We designed this meter to measure household
AC voltage. It is not intended for commercial or
industrial use. If you want to measure 3-phase,
line-to-line voltages, please note the following.
‘Waming: Because of the dangers inherent in
measuring three-phase circuits, we strongly re-
commend that you do not use this meter for such
applications.