Tenma 72-7740 User manual

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Unpacking Inspection
Rules For Safe Operation
Title Page
Table of Contents
1
D. Continuity Test
International Electrical Symbols
AC Voltage Measurement
Capacitance Measurement
The Use of Relative Value Mode
The Meter Structure
Turning on the Display Backlight
General Specifications
Resistance
Overview
Safety Information
Rotary Switch
Functional Buttons
Display Symbols
Measurement Ranges
A.
B.
Measurement Operation
A.
B.
C.
D. Testing for Continuity
E.
F.
G.
H.
I. Temperature Measurement
J.
Operation of Hold Mode
ThePOWER Button
TheBLUE Button
Sleep Mode (Model 72-7740 only)
Accuracy Specifications
A. DC Voltage
B. AC Voltage
C.
Selecting a Measurement Range
Manual Ranging and Autoranging
DC Voltage Measurement
Measuring Resistance
Frequency Measurement
DC or AC Current Measurement
Testing Diodes
Measuring Duty Cycle
Model 72-7740/72-7745: OPERATING MANUAL

Capacitance
Frequency & Duty Cycle
DC Current
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Page
2
J. AC Current
Maintenance
A. General Service
B. Testing the Fuses
C. Replacing the Battery
D. Replacing the Fuses
RS232C Serial Port (Model 72-7745)
A. RS232C Port Cable
B. Setting of RS232C Serial Ports
C. System Requirements for
Installing the serial Interface Program
Diode Test
I.
E.
F.
G.
H. Temperature
Model 72-7740/72-7745: OPERATING MANUAL

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Overview
This Operating Manual covers information on safety and
cautions. Please read the relevant information carefully
and observe all the Warnings and Notes strictly.
Warning
To avoid electric shock or personal injury, read the
“Safety Information” and “Rules for Safe Operation”
carefully before using the Meter.
Digital Multimeter Model 72-7740 (hereafter referred to
as “the Meter”) have autorange and manual range options
with maximum reading 3999. The enclosure structure
design adopted advanced “co-injection” technique in
order to provide sufficient insulation.
Model 72-7740/72-7745: OPERATING MANUAL

Qty
1 piece
1 pair
1 pair
1 piece
1 piece
Item
1
2
3
4
5
Description
Operating Manual
Test Lead
Test Clip
CAT IV: Primary supply level, overhead lines, cable
systems etc.
4
Unpacking Inspection
Open the package case and take out the Meter. Check the
following items carefully to see any missing or damaged part:
In the event you find any items missing or damaged,
please contact your dealer immediately.
Safety Information
This Meter complies with the standards IEC61010: in
pollution degree 2, overvoltage category (CAT. III 1000V,
CAT. IV 600V;)and double insulation.
CAT. III: Distribution level, fixed installation, with smaller
transient overvoltages than CAT. IV
Use the Meter only as specified in this operating manual,
otherwise the protection provided by the Meter may be
impaired.
In this manual, a Warning identifies conditions and
actions that pose hazards to the user, or may damage
the Meter or the equipment under test.
A Note identifies the information that user should pay
attention to.
International electrical symbols used on the Meter and
in this Operating Manual are explained on page 6.
Point Contact Temperature Probe
9V Battery (NEDA1604, 6F22 or 006P)
(installed)
Model 72-7740/72-7745: OPERATING MANUAL

Rules For Safe Operation
To avoid possible electric shock or personal injury, and to
avoid possible damage to the Meter or to the equipment
under test, adhere to the following rules:
lBefore using the Meter inspect the case. Do not use the
Meter if it is damaged or the case (or part of the case) is
removed. Look for cracks or missing plastic. Pay
attention to the insulation around the connectors.
lInspect the test leads for damaged insulation or exposed
metal. Check the test leads for continuity. Replace
damaged test leads with identical model number or
electrical specifications before using the Meter.
lDo not apply more than the rated voltage, as marked on
the Meter, between the terminals or between any
terminal and ground.
lThe rotary switch should be placed in the correct
position and no change of range made during
measurement , to prevent damage of the Meter.
lWhen working at an effective voltage over 60V
DC or 30V rms AC, special care should be taken
there is danger of electric shock.
lUse the proper terminals, function, and range for your
measurements.
lDo not use or store the Meter in an environment of high
temperature, humidity, explosive, flammable and
strong magnetic field. The performance of the Meter
may deteriorate after dampened.
lWhen using the test leads, keep your fingers behind the
finger guards.
lDisconnect circuit power and discharge all high-voltage
capacitors before testing resistance, continuity, diodes,
current, or capacitance.
lBefore measuring current, check the Meter’s fuses and
turn off power to the circuit before connecting the Meter
to the circuit.
lReplace the battery as soon as the battery indicator " "
appears. With a low battery, the Meter might produce
false readings that can lead to electric shock and
personal injury.
lRemove test lead, temperature probe, RS232C interface
Warning
5
Model 72-7740/72-7745: OPERATING MANUAL

cable and test clip from the Meter and turn the Meter
power off before opening the case.
lWhen servicing the Meter, use only the same model
number or identical electrical specifications replacement
parts.
lThe internal circuit of the Meter shall not be altered at
will to avoid damage of the Meter and any accident.
lSoft cloth and mild detergent should be used to clean the
surface of the Meter when servicing. No abrasive and
solvent should be used to prevent the surface of the Meter
from corrosion, damage and accident.
l
l
l
l
The Meter is suitable for indoor use.
Under the environment with high (+/-4kV) electrostatic
discharge, the Meter may not be operated as normal
condition. The user may require resetting the Meter.
Remove the battery when not used for a prolonged
period to avoid damage to the Meter.
Please constantly check the battery as it may leak
when it has been using for some time, replace the
battery as soon as leaking appears. A leaking battery
will damage the Meter.
6
International Electrical Symbols
AC (Alternating
Current) Deficiency of Built-In Battery
DC (Direct Current) Continuity Test
AC or DC Diode
Grounding Capacitance Test
Double Insulated Fuse
Warning. Refer to the
Operating Manual Conforms to Standards of European Union
Model 72-7740/72-7745: OPERATING MANUAL
lPeriodically check the battery as it may leak after
some time. If leakage is apparent,the battery should
be immediately replaced to prevent damage.

The Meter Structure(see figure 1)
(figure 1)
1 LCD Display
2 Functional Buttons
3 Rotary Switch
4HzV Input Terminal:
Input for voltage, frequency/duty cycle, resistance, diode,
continuity and capacitance measurements.
5COM Input Terminal:
Return terminal for all measurements.
Input Terminal:
Input for 0.1 A to 400.0mA current measurements and
temperature testing.
710A Input Terminal:
Input for 0.01A to 10.00A current measurements.
7
Model 72-7740/72-7745: OPERATING MANUAL

8
Rotary Switch
The table below provides information about rotary switch
positions.
Rotary
Switch
Position Function
VDC voltage measurement range from 400.0mV to
1000V or
AC voltage measurement range from 4.000V to
750.0V.
Continuity test.
Diode test.
Resistance measurement range from 400.0
Temperature in celsius
Hz Frequency measurement range from 10.00Hz to
10.00MHz.
AC or DC current measurement range from
A.
mA AC or DC current measurement range from
40.00mA to 400.0mA.
AAC or DC current measurement range from
4.000A to 10.00A.
to 40.00M .
Model 72-7740/72-7745: OPERATING MANUAL

Functional Buttons (1)
9
The table below provides information about functional
button operation.
Button Measuring
Function Operation Performed
POWER Any rotary
switch
position
Turn the power on and off.
VSwitches between AC and DC
voltage; the Meter beeps. DC is
default.
Switches between continuity and
diode and resistance and
capacitance measurements; the
Meter beeps.
Resistance is default.
Switches between AC and DC
current range from 400.0 A to
4000 A; the Meter beeps. DC is
default.
mA Switches between AC and DC
current range from 40.00mA to
400.0mA; the Meter beeps. DC is
default.
ASwitches between AC and DC
current range from 4.000A to
10.00A; the Meter beeps. DC is
default.
Disable Sleep Mode feature.
(BLUE)
Model 72-7740/72-7745: OPERATING MANUAL

RANGE
Any rotary
switch
position
exceptHz
and
lPressRANGE to enter the
manual ranging mode; the Meter
beeps.
Manually selecting a range causes
the Meter to exit the Hold and REL
modes.
lPressRANGE to step through
the ranges available for the
selected function; the Meter beeps.
lPress and hold RANGEfor 2
seconds to return to autoranging;
the Meter beeps.
Hz 1. Press to start the frequency
counter; the Meter beeps.
2. Press again to enter duty cycle
mode; the Meter beeps.
3. Press again to return to the
frequency counter mode; the Meter
beeps.
Hz %
V, ,
mA or
A
1. Press to start the frequency
counter; the Meter beeps.
2. Press again to enter duty cycle
mode; the Meter beeps.
3. Press again to return to the
previous measurement mode; the
Meter beeps.
REL
Any rotary
switch
position
except Hz
Press to enter
and exit the REL mode in any
measuring mode except in
frequency/duty cycle; the Meter
beeps.
Any rotary
switch
position
PressHOLD H to enter and exit
the Hold mode in any mode, the
Meter beeps.
REL
Functional Buttons (2)
HOLD H
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Model 72-7740/72-7745: OPERATING MANUAL

Display Symbols (1)
(see figure 2)
Number Symbol Meaning
1AC Indicator for AC voltage or current.
Model 72-7740:The displayed value is the
mean value.
Model 72-7745:The displayed value is
the true rms value.
2 TRMS Model 72-7745: Indicator for true rms
value.
3 The Meter is in the auto range mode in
which the Meter automatically selects the
range with the best resolution.
4 RS232CData output. It is always on the LCD, but
data output is only in progress when the
Meter is connected to the computer via the
included RS232C Interface Cable.
5% Percent: Used for duty cycle measurements.
6Data hold is active.
7The REL is on to display the present value
minus the stored value.
8The battery is low.
Warning To avoid false readings,
which could lead to possible electric shock
or personal injury, replace the battery as
soon as the battery indicator appears.
9 Centigrade. The unit of temperature.
10 Diode test.
11 The continuity buzzer is on.
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1
234567 8 9 10
11
12 ~ 16
17
(figure 2)
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Model 72-7740/72-7745: OPERATING MANUAL

, k ,
M: k:
M:
Ohm. The unit of resistance.
kilohm. 1 x 10 or 1000 ohms.
Megaohm. 1 x 10 or 1,000,000 ohms.
nF F:
nF:
Farad. The unit of capacitance.
Microfarad. 1 x 10or 0.000001
farads.
Nanofarad. 1 x 10 or 0.000000001
farads.
Hz,
kHz,
MHz
Hz:
kHz:
MHz:
Hertz. The unit of frequency in
cycles/second.
Kilohertz. 1 x 10or 1,000 hertz.
Megahertz. 1 x 10 or1,000,000
hertz.
V, mV V:
mV Volts. The unit of voltage. Millivolt. 1 x 10 or 0.001 volts.
12~16
A, mA, A:
mA: Amperes (amps). The unit of current.
Milliamp. 1 x 10 or 0.001 amperes.
Microamp. 1x 10 or 0.000001
amperes.
17 Indicates negative reading.
18 The input value is too large for the selected
range.
Measurement Ranges (1)
The Meter has both manual range and autorange options:
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Display Symbols (1) (see figure 2)
A measurement range determines the highest value the Meter
can measure. Most Meter functions have more than one range.
See “Accuracy Specifications.”
A.Selecting a Measurement Range
Choosing the correct measurement range is important:
lIf the range is too low for the input, the Meter displays to
indicate an overload.
lIf the range is too high, the Meter will not display the most
accurate measurement.
B. Manual Ranging and Autoranging
Model 72-7740/72-7745: OPERATING MANUAL

lIn the autorange mode, the Meter selects the best range for
input signals.
This allows you to switch test points without having to reset
the range.
lIn the manual range mode, you may select the range.
This allows you to override autorange and lock the Meter in a
specific range.
The Meter defaults to the autorange mode in measurement
functions that have more than one range. When the Meter is in
the autorange mode,
To enter and exit the manual range mode:
1. Press RANGE.
The Meter enters the manual range mode and turns off.
Pressing RANGE increments the range. When the highest
range is reached, the Meter wraps to the lowest range.
Measurement Ranges (2)
Note
lIf you manually change the measurement range after entering
the REL or Hold recording modes, the Meter exits these
modes.
lUnder frequency/duty cycle and capacitance measurement,
only autorange mode is available.
2. To exit the manual range mode, press and hold RANGE for
two seconds.
The Meter returns to the autorange mode and is displayed.
is displayed.
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Model 72-7740/72-7745: OPERATING MANUAL

Measurement Operation (1)
A.DC Voltage Measurement
(see figure 3)
(figure 3)
To avoid harm to you or damage to the Meter from
electric shock, please do not attempt to measure voltages
higher than 1000VDC / 750VAC rms although readings
may be obtained.
The DC Voltage ranges are: 400.0mV, 4.000V, 40.00V, 400.0V
and 1000V. To measure DC voltage, connect the Meter as
follows:
1. Insert the red test lead into the terminal and the black
test lead into theCOMterminal.
2. Set the rotary switch to ; DC measurement is default or
press BLUE button to select DC measurement mode.
3. Connect the test leads across with the object being measured.
The measured value shows on the display.
Note
lIn each range, the Meter has an input impedance of 10M.
This loading effect can cause measurement errors in high
impedance circuits. If the circuit impedance is less than or
equal to 10k , the error is negligible (0.1% or less).
lWhen DC voltage measurement has been completed,
disconnect the connection between the test leads and the
circuit under test, and move the test leads away from the
input terminals of the Meter.
Warning
HzV
V
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Model 72-7740/72-7745: OPERATING MANUAL

Measurement Operation (2)
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B. AC Voltage Measurement
(see figure 4)
(figure 4)
the true root mean square value converter needs a longer
time to stabilize.
To avoid harm to you or damage to the Meter from
electric shock, please do not attempt to measure voltages
higher than 1000VDC / 750VAC rms although readings
may be obtained.
Warning
The AC voltage ranges are: 4.000V, 40.00V, 400.0V and
750.0V. To measure AC Voltage, connect the Meter as follows:
1. Insert the red test lead into the terminal and the black
test lead into the COM terminal.
2. Set the rotary switch to and press BLUEbutton to select
AC measurement.
3. Connect the test leads across with the object being measured.
The measured value shows on the display.
Note
lIn each range, the Meter has an input impedance of 10M.
This loading effect can cause measurement errors in high
impedance circuits. If the circuit impedance is less than or
equal to 10k , the error is negligible (0.1% or less).
lWhen AC voltage measurement has been completed,
disconnect the connection between the testing leads and the
circuit under test, and remove the testing leads away from the
input terminals of the Meter.
lTrue root mean square (TRMS)value stability period(Model
72-7745): When the reading obtained is less than 100 digits,
When there is no input voltage, the maximum reading
displayed is 10 digits.
HzV
V
Model 72-7740/72-7745: OPERATING MANUAL

To avoid damage to the Meter or to the devices under test,
disconnect circuit power and discharge all the high-voltage
Warning
C.Measuring Resistance
(see figure 5)
Measurement Operation (3)
(figure 5)
from the reading.
The resistance ranges are: 400.0 , 4.000k , 40.00k,
400.0k , 4.000M and 40.00M . To measure resistance,
connect the Meter as follows:
1. Insert the red test lead into theHzV terminal and the black
test lead into theCOM terminal.
2. Set the rotary switch to ;
resistance measurement
( ) is default or pressBLUE button to select measurement
mode.
3. Connect the test leads across with the object being measured.
The measured value shows on the display.
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capacitors before measuring resistance.
Note
lThe test leads can add 0.1 to 0.2 of error to resistance
measurement. To obtain precision readings in low-resistance
measurement, that is the range of 400.0 , short-circuit the
input terminals beforehand, using the relative measurement
function buttonREL to
measured when the testing leads are short-circuited
automatically subtract the value
Model 72-7740/72-7745: OPERATING MANUAL

lIf reading with shorted test leads is not 0.5 , check for
loose test leads, incorrect function selection, or enabled Data
Hold function.
lFor high-resistance measurement ( ), it is normal to
take several seconds to obtain a stable reading.
lThe LCD displays indicating open-circuit for the tested
resistor or the resistor value is higher than the maximum
range of the Meter.
lWhen resistance measurement has been completed,
disconnect the connection between the test leads and the
circuit under test, and remove the test leadsfrom the
input terminals of the Meter.
D.Testing for Continuity
(see figure 6)
Measurement Operation (4)
(figure 6)
To avoid damage to the Meter or to the device under test,
disconnect circuit power and discharge all the high-voltage
capacitors before testing for continuity.
To test for continuity, connect the Meter as below:
1. Insert the red test lead into theHzV terminal and the black
test lead into the COMterminal.
2. Set the rotary switch to
measurement mode.
3. The buzzer sounds if the resistance of a circuit under test is
less than around 70
Warning
and press BLUE button
to select
Note
lThe LCD displays indicating the circuit being tested is
open.
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Model 72-7740/72-7745: OPERATING MANUAL

E. Testing Diodes
(see figure 7)
To avoid possible damage to the Meter and to the device
under test, disconnect circuit power and discharge all high-
voltage capacitors before testing diodes.
Use the diode test to check diodes, transistors, and other
semiconductor devices. The diode test sends a current through
the semiconductor junction, and then measures the voltage drop
across the junction. A good silicon junction drops between
0.5V and 0.8V.
Warning
lWhen continuity testing has been completed, disconnect the
connection between the test leads and the circuit under
test, and remove the test leads from the input terminals
of the Meter.
3. For forward voltage drop readings on any semiconductor
component, place the red test lead on the component’s anode
and place the black test lead on the component’s cathode.
The measured value shows on the display.
Note
lIn a circuit, a good diode should still produce a forward
To test a diode out of a circuit, connect the Meter as follows:
Insert the red test lead into theHzV terminal and the black
testlead into theCOM terminal.
2. Set the rotary switch to
measurement mode.
and press BLUE button
to select
Measurement Operation (5)
(figure 7)
1.
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Model 72-7740/72-7745: OPERATING MANUAL

Measurement Operation (6)
F.Capacitance Measurement
(see figure 8)
voltage drop reading of 0.5V to 0.8V; however, the reverse
voltage drop reading can vary depending on the resistance of
other pathways between the probe tips.
lConnect the test leads to the proper terminals as said above to
avoid error display. The LCD will display indicating
diode being tested is open or polarity is reversed.The unit of
diode is Volt (V), displaying the forward voltage drop
readings.
lWhen diode testing has been completed, disconnect the
connection between the testing leads and the circuit under
test, and remove the testing leads away from the input
terminals of the Meter.
(figure 8)
Warning
Insert the red test lead into theHzV terminaland the
black test lead into the COM terminal.
2.Set the rotary switch to
measurement mode.
and press BLUE
button to selectnF
3. Connect the test leads across with the object being
measured. The measured value shows on the display.
Note
lFor testing polarited capacitors, connect the red clip to
To avoid damage to the Meter or to the equipment under
test, disconnect circuit power and discharge all high-voltage
capacitors before measuring capacitance. Use the DC
Voltage function to confirm that the capacitor is discharged.
1.
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Model 72-7740/72-7745: OPERATING MANUAL

input terminals of the Meter.
input terminals of the Meter.
Measurement Operation (7)
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anode & black clip to cathode instead of using test leads as
mentioned above.
lTo minimize the effect of capacitance stored in the test leads,
the test lead should be as short as possible. To measure a
small value of capacitance, use REL mode to remove the
leads capacitance. Remaining voltage, insulated impedance,
& dielectric absorption from the capacitor may cause slight
measurement error.
lHigher value capacitors will require additional time for
measurement.The 100 F range requires up to 15 seconds.
lThe LCD displays indicating the tested capacitor is
shorted or it exceeds the maximum range.
lWhen capacitance measurement has been completed,
disconnect the connection between the test leads and the
circuit under test and remove the test leads from the
The measured value shows on the display.
The measurement range is from 10Hz to 10MHz. To measure
frequency, connect the Meter as follows:
1. Insert the red test lead into theHzV terminal and the black
test lead into the COM terminal.
2. Set the rotary switch toHz; frequency measurement (Hz) is
default or press Hz % to select Hz measurement mode.
3. Connect the test leads across with the object being measured.
G. Frequency Measurement
(see figure 9)
Note
lWhen frequency measurement has been completed,
disconnect the connection between the test leads and the
circuit under test, and remove the test leads from the
(figure 9)
Model 72-7740/72-7745: OPERATING MANUAL