Matrix MDM8145A User manual

USER MANUAL
Digital Multimeter
Model MDM8145A, MDM8146A, MDM8155A
© Copyright belongs to Matrix
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USER MANUAL

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Contents
1. Safety Notices............................................................................................................... 2
2. Introduction ................................................................................................................... 5
3. General indicators......................................................................................................... 7
4 Quick reference.............................................................................................................. 7
4.1 Check the accessories of the product.................................................................. 7
4.2 The front panel at a glance .................................................................................. 8
4.3 Introduction to keys.............................................................................................. 9
4.4 Introduction to the display.................................................................................. 14
4.5 Introduction to the back panel............................................................................ 15
4.6 Adjustment of handle ......................................................................................... 16
4.7 Turn on the multimeter....................................................................................... 17
5 Instruction on measurement......................................................................................... 17
5.1 Voltage measurement........................................................................................ 18
5.2 Current measurement........................................................................................ 20
5.3 Resistance measurement .................................................................................. 23
5.4 Capacitance measurement................................................................................ 25
5.5 Frequency measurement................................................................................... 26
5.6 Diode and on-off test.......................................................................................... 27
5.7 Duty cycle measurement.................................................................................... 29
5.8 Square wave output........................................................................................... 30
6 Technical indicators ..................................................................................................... 32
7 Calibration.................................................................................................................... 36
8 Communication interface ............................................................................................. 43
9. Installation and use of relevant software..................................................................... 44
10. Maintenance and upkeep.......................................................................................... 44

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1. Safety Notices
To avoid personal injury and prevent damage to the product, be sure to use this
product in accordance with the manual. Before fully understanding and meeting the
following warning, do not proceed to the next step.
Safety ground. The safety ground must be firmly connected to the ground pin at
the power outlet and insert the instrument plug into a grounded outlet.
Use proper fuses. To provide continuous fire protection, use only the specified
type and rating fuses.
Proper use of lead set. Do not use damaged or worn test lead set. It may result
in damage to the instrument or personal injury. When using probes, the finger
should be kept behind the finger protector of the probe. When wiring, should
connect the common line first and then connect the charged test lead. When
disconnecting, disconnect the charged test lead first.
If the product malfunctions, do not use. Its protection may be impaired, do not
install substitute parts or perform any unauthorized modification to the product.
Please return the product for repair or to be checked by a professional inspection
to ensure product’s safety features.
Do not use this product at high temperature, or environment with
explosives or strong electromagnetic field.
Do not change the internal wiring inside of instrument, so as not to damage
the instrument or cause other endanger the safety of things.
When measuring, the correct measurement function and range must be
selected.
Before the function range is switched, to prevent damage to the instrument,
the probe and the measured circuit should be disconnected to prevent
damage to the instrument.
Protection limits.
The Digital Multimeter provides protection circuitry to prevent damage to the
instrument and to protect against the danger of electric shock provided the Protection
Limits are not exceeded. To ensure the safe operation of the instrument, do not exceed
the Protection Limits shown on front and back panels, and defined as follows:

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Table 1 Different functions of input terminals
Measurement function
Input terminals Overload protection
DC voltage
INPUT
LO
1000V DC or 750V AC
AC voltage 1000V DC or 750V AC
Frequency 250V DC and AC peak
2W resistance 1000V DC or 750V AC
Capacitance 250V DC and AC peak
Diode and on-off 250V DC and AC peak
AC and DC current mA mA
Overload protection:
500mA/250V
fuse, 11A/250V fuse
AC and DC current A 10A
4W resistance SENSE HI
INPUT HI
SENSE LO
INPUT LO
250V DC and AC peak
Notes:
In order to avoid blown fuse or damage to the meter, be sure to follow these tips to
use the current input terminals.
1) 10 A and 200 mA input terminals are not allowed to simultaneously connect to the
current measurement circuit.
2) If the effective value of the measured current AC + DC is within the range from 200
mA to 10 A, only 10A and LO terminals are allowed to be used in the measurement.
3) When the measurement of current is conducted, before the multimeter is powered

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on, be sure to select the proper current input terminals based on the estimation.
4) The current input to the terminal 10 Amust not exceed 11A; otherwise, the internal
fuse inside the multimeter will blow; and the current input to 200 mA terminal must not
exceed 500 mA; otherwise, the current input fuse on the back panel will blow.
IEC Measurement Category II Overload Protection
To protect against the danger of electric shock, this product provides overload
protection for line-voltage mains connections meeting both of the following conditions:
1 . The HI and LO input terminals are connected to the mains under the Measurement
Category II (as described below) conditions.
2 . The mains are limited to a maximum line voltage of 300 VAC.
Warning: IEC Measurement Category II includes electrical devices connected to
mains at outlet on a branch circuit. Such devices include most small appliances, test
equipment, and other devices that plug into a branch outlet socket.
This product can be used for such measurements: HI and LO inputs are connected to
mains of such devices (up to 300 VAC), or to the branch outlet. However, this product may
not used with its HI and LO inputs connected to the mains in permanently installed
electrical devices, such as the main circuit-breaker panel, sub-panel disconnected boxes,
or permanently wired motors. Such devices and circuits are subject to over voltages that
may exceed the protection limits of this product.
Notes: Voltages above 300 VAC can be measured only in circuits that are isolated
from mains. However, transient over voltages are also present on circuits that are isolated
from mains. This product is designed to safely withstand occasional transient can over
voltages up to 2500Vpk. Do not use this equipment to measure circuits where transient
overvoltages could exceed this level.
Environment related notes
This product complies with the WEEE Directive (2002/96 / EC) marking requirement.
The affixed product label (see below) indicates that you must not discard this electrical /
electronic product in domestic household waste.
Product category: With reference to the equipment types in the WEEE directive
Annex 1, this product is classified as a "Monitoring and Control instrumentation" product.
This product may contain substances that might be harmful to the environment or

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human health; in order to avoid the release of hazardous substances into the environment
or harm to human health, we recommend the use of appropriate methods to recycle this
product in order to ensure that most of the materials are reused or recycled. For disposal
or recycling related information, please contact the local authorities.
Safety Symbols
The following signs might be seen on the product:
Earth ground Chassis ground Risk of electric shock Refer to manual for
additional safety information
2. Introduction
MDM8145A / MDM8146A / MDM8155A is a full-featured, 19999 counting 4½ digit (MDM8145A /
MDM8146A) / 199999 counting 5½ digits (MDM8155A) desk-type true-RMS digital multimeter with
stable performance. The STM32 chip and external integration AD chip used by the meter offer strong
overall functionality, excellent performance, and good experience for users; its 3.5-inch large-screen
has clear displays of reading, rich content, and a good result of display. It is mains-powered driving
which makes it highly reliable. Its comprehensive features, full-range overload protection and unique
design make it the first choice for electricians and university laboratories.
In addition, MDM8145A / MDM8146A / MDM8155A are equipped with the calibration function
which allows the user to calibrate according to actual needs and is simple and convenient.
Basic features
5½-digit resolution ratio (MDM8155A) / 4½-digit resolution ratio (MDM8145A / MDM8146A).
3.5-inch large-screen display with rich content, clear display of reading, and a good result of display.
Dual parameter display: it can display two parameters of the same input signal (for example, with the AC
voltage measurements, it can display simultaneously AC voltage and AC frequency value).

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Measurement speed points: FAST (6 times / second) → MID (4 times / sec) → SLOW (1 times / sec).
Duty cycle measurement function
Square wave output function (MDM8145A and MDM8146A optional)
Manual / automatic range setting function
Communication interfaces: USB Device, RS232 (MDM8145A and MDM8146A optional).
Support SCPI protocol and provide programming file
AC and DC voltage, DC current, two-wire / four-wire resistance measurement.
Cycle and frequency measurement, frequency of up to 20MHz.
Capacitance measurement.
Provide automatic trigger, external trigger, and single trigger measurements. (External trigger optional for the
MDM8145A and MDM8146A models).
Measurement capabilities for current up to 10A and voltage up to 1000V DC.
Keypad lock function and system setup; languages, buzzer, screen brightness and so on can be configured
according to various needs.
Simple external calibration function
Variety of mathematical functions: statistics (maximum, minimum), relative measurement, dB, dBm.
On-off, diodes, reading hold, data hold / reading, key tone, trigger measurement and so on.

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3. General indicators
1-1 Mode of display: 3.5-inch LCD display;
1-2 Maximum display: 220 000 (5 1/2) automatic polarity display and unit digit
display;
1-3 Range selection: automatic / manual;
1-4 Note to over-range: the screen displays "-OL-";
1-5 Measuring rate: fast (6 times / sec), medium (4 times / sec), slow (1 times /
sec);
1-6 Power supply voltage: AC 220V ± 10%, 50Hz;
1-7 Working environment: (0 ~ 40) ℃, relative humidity <80%;
1-8 Storage environment: -10 ~ 50 ℃, relative humidity <80%;
1-9 Dimensions: 265mm x 105mm x 330mm (width X height X depth);
10 Weight: 2.3kg;
4 Quick reference
4.1 Check the accessories of the product
Confirm the following accessories of the multimeter, among which the optional
accessories are delivered if only ordered. If any items are missing, please contact the
nearest sales office.
4½ digits standard accessories:
a pair of probes
a double end three-wire power line
two backup power fuses
MDM81 user’s manual
5½ digits standard accessories:
a pair of probes
a double end three-wire power line
a CD-ROM

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two backup power fuses
MDM81 user’s manual
Optional accessories:
RS232 serial line
USB cable
Standard and optional function / information of communication interface
Function/communication interface Four and a half digits Five and a half digits
USB Device Standard Standard
RS232 Optional Standard
Square wave output Optional Standard
External trigger Optional Standard
4.2 The front panel at a glance
The front panel of the table-type multimeter is shown in Figure 1.1.1.
Figure 1.1.1 Sketch map of front panel
Table 1.1.1 Description of each module of front panel
No. Description
1 measurement terminal of multimeter
2 displayscreen
3 basic measurement function keys
4 parameter selection Enter keys
5 mathematical function keys
6 additional function keys
7 powerkey

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4.3 Introduction to keys
See Figure 1.2.1 for keys:
RELdBmdBMINMAX
Enter
Freq
Period
AC V
DC V
-|(-AC I
DC I
SHIFT
TRIG
EXT
CAL
AUTO
LO
MEM
HI
SAVE
EXIT
SYS
Cont
2W 4W
Ω
HOLD
DUTY
AD+DC
Figure 1.2.1 Keys
Switch of multimeter
Press the key to turn on or off the meter.
The basic measurement function keys
DC V
Press the key to enter the DC voltage measurement interface;
AC V
Press the key to enter the AC voltage measurement interface;
DC I
Press the key to enter the DC current measurement interface;
AC I
Press the key to enter the AC current measurement interface;
2W 4W
Ω
Press the key to enter 2W resistance measurement interface, and press this
key again to enter 4W resistance measurement interface;
-|(-
Press the key to enter capacitance measurement interface;
Freq
Period
Press the key to enter frequency measurement interface, and press this key
again to enter the cycle measurement interface;
Cont
Press the key to enter the diode measurement interface, and press this key
again to enter the on-off measurement interface;
Parameter selection keys
、

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Function:
1. Press the key to switch from automatic range to manual range and switch the range;
2. Adjust the frequency of the square wave output;
3. Browse the stored data;
4. Adjust the upper and lower limits;
、
Function:
1. Change the measurement speed;
2. Select the position where the square wave needs adjustment;
3. Select the position where the upper and lower limits need adjustment;
Enter
Function:
1. Enter key.
2. Proceed to set the frequency of the square-wave
3. Proceed to set the limits
Additional function keys
HOLD
DUTY
Press the key to start duty cycle measurement;
TRIG
EXT
Single-trigger key, each time it is pressed, it measures and displays for
one time;

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CAL
AUTO
1. When the range is in manual mode, press the key to switch to the
automatic range;
2. When the trigger mode is not automatic, press this key to switch to the automatic
trigger;
AC+DC
Square wave output key, press the key to output a square wave signal
with fixed amplitude and tunable frequency. Press the Enter key to enter the frequency
adjustment, control the arrow keys to adjust, and then press the Enter key after the
adjustment is done. (five and a half digits standard, four and a half digits optional, and
peripheral circuit is required)
HI
SAVE
Press the key to enter the data storage mode, and press the key again
to exit the data storage mode. When it is in data storage mode, every time the
measurement is done, the measured data and the current measurement configuration will
be written into the cache, and the storage number will be displayed. In the meantime, you
can switch to a different measurement function (storage is not supported for some
functions, such as diodes, duty cycle, on-off measurement, etc.); for each measurement
function the measurement data will be saved. When the key is pressed to exit the storage
mode, the system automatically writes the data in the cache into FLASH. There can be up
to 600 storage data, when there are more than 600 data, it will save the 600 data from the
latest one. However, the counting starts again from 1 because there are more than 600
data displayed.
LO
MEM
Data reading key, press the key to enter the data reading mode, and
press the other keys (DCV, DCI and the like) or Exit (SHIFT + EXIT) to exit. When entering
the data reading mode, the first display is the last number of the last saved data. In
addition to the data on the main display, the serial number of the last saved data and
some measurement configuration (measurement function, range, measurement rate,
trigger mode and additional functions) will be displayed on the secondary display. Press
the arrow keys to browse the saved data. The latest saved is seen first in the reading

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mode; so there is no need to browse the following data. When the saved number exceeds
600, for example 65-, then the 650th data is shown when entering the reading mode, and
50 is shown on the secondary display. The number decreases on the second display
when browsing the previous data. When 1 is shown on the secondary display, then
browse the previous data and it will display 600. That is to say, saving and reading are
conducted in circular manner.
EXIT
SYS
System information checking setting key, press the key to view the
current model, serial number, software version, and language, buzzer, screen brightness
and so on can be set. Use the arrows keys to select and change.
SHIFT
Second function enable key
SHIFT
+
HOLD
DUTY
Reading hold function, press the key combination, the reading on
the meter remains; and press the key combination again to exit the reading hold function.
SHIFT
+
AC+DC
AC + DC measurement function, press the key combination to
start AC + DC signal measurement; press the key combination again to exit the reading
hold function. (The function cannot be applied currently)
SHIFT
+
TRIG
EXT
External trigger function, press the key combination to enter the
external trigger measurement mode; when a low pulse flows through the external trigger
terminal, the system measures one time; press the key combination again to exit the
external trigger function. (MDM8155A standard function, MDM8145A / MDM8146A
optional function)
SHIFT
+
CAL
AUTO
Calibration function, press the key combination to enter the
calibration mode. However, the calibration function is related to what the measurement
function is when entering the calibration mode. For example, when the current
measurement function is DCV, then press the key combination and it will enter the
calibration mode of DCV. The measurement functions which support calibration function
are: DC/AC voltage, DC/AC current, two- and four-wire resistance, capacitance.

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SHIFT
+
HI
SAVE
Upper limit comparison function, which is only effective in case of
AC and DC voltage. When it is switched to the AC and DC voltage measurement function,
press the key combination to enter the upper limit comparison function and the default
comparison value is 1V; press the Enter key to set the comparison value, press the arrow
keys to change the comparison value, and then press Enter to complete the setting. When
the displayed value is larger than the comparison value, the buzzer will ring out; otherwise,
it will not.
SHIFT
+
LO
MEM
Lower limit comparison function, which is only valid in case of AC
and DC voltage. In the AC and DC voltage measurement function, press the key
combination to enter the lower limit comparison function and the default value is 1V; press
Enter to set the comparison value, and press the arrow keys to change the comparison
value, then press Enter to complete the setting. When the displayed value is larger than
the comparison value, the buzzer will ring out; otherwise, it will not.
SHIFT
+
EXIT
SYS
Exit key, press the key combination to exit from all additional
functions and return to DC voltage measurement interface in any state or in case of any
function.
Mathematical function key
dB
Press the key and dB value will be shown on the secondary display; it is only
valid in case of the AC and DC voltage measurement function. dB value = dBm value
of the reading - dBm value of the relative value;
dBm
Press the key and dBm value will be shown on the secondary display; it is
only valid in case of the AC and DC voltage measurement function. dBm = 10 x log10
(reading 2/ reference resistor / 1mW);
REL
Relative measurement key, press the key, and it will record the current value,
and the displayed value afterward= actual measured value - current recorded value;

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MAX
Maximum measurement key; press the key, and the system will determine
according to the measured values, and the maximum value is displayed on the
secondary display
MIN
Minimum measurement key; press the key, and the system will determine
according to the measured values, and the minimum value is displayed on the
secondary display
4.4 Introduction to the display
DCV
1.99999
AUTO
V
100
%
AUTO 2V
AUTO TRI
Slow Local
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3
4
5
6
Figure 1.3.1 Interface of the display
Table 1.3.1 Interface Module Description
No. Note
1 displays the function currently under operation
2 displays the mode of trigger: automatic trigger, single trigger,
external trigger
3 only di
splays when it is in the automatic range and hint at the
currently corresponding range
4 maindisplay
5 secondary display
6 measurement configuration column
Details of measurement configuration column
The first pane displays the range: take the DC voltage for example, there are modes

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such as automatic (AUTO), 200mV, 2V, 20V, 200V, 1000V. When in automatic (AUTO)
mode, the information represented by the number 3 appears.
The second pane shows the measurement speed: There are three kinds of
measurement speeds to choose from—slow (SLOW), Medium (MIDDLE), fast (FAST).
The third and fourth panes are mainly used to display the operation function, when
running the functions such as save (SAVE), (read) MEM, compare (COMP), external
trigger (EXT), and DC + AC, the corresponding function information is shown on the third
and fourth panes.
The fifth pane displays whether the mode is local or remote.
4.5 Introduction to the back panel
Figure 1.5.1(1) Sketch map of five and a half digits back panel

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Figure 1.5.1(2) Sketch map of four and a half digits back panel
Table 1.5.1 Description of back panel
No. Description
1 supply hub: AC 220V/50Hz power supply input socket
2 power fuse: 0.5A/250V fuse
3 voltage selector: 110V/50Hz VAC or 220V/50Hz VAC
4 RS232 interface（MDM8145A/MDM8146A optional）
5 USB Device interface
6 square wave output terminal（MDM8145A/MDM8146A optional）
7 external trigger measurement port（MDM8145A/MDM8146A optional）
8 current input fuse: 0.5A/250V fuse
4.6 Adjustment of handle
To adjust the carrying handle of the digital multimeter, hold the handle by the sides
and pull it outward. Then rotate the handle to the required position. See the figure below
for the operation method
Adjust Handle
Working position Carrying
position

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4.7 Turn on the multimeter
1. Connect the AC power supply
1) The power supply of 110V or 220V for the multimeter can be selected, adjust the
voltage selector on the back panel of the multimeter according to the power supply.
2) Use the power line provided to connect the multimeter to AC power.
2. Start multimeter
Turn on the power switch below the power socket.
3. If the instrument does not start, check according to the following steps:
1) Check if the power line has a good contact.
2) Check if the back panel is turned on.
3) If there is no problem after the inspection, and the instrument still does not start,
check if the power fuse is blown; if necessary, replace the fuse.
4) If after the above checks, the instrument still does not start, please contact the
relevant department.
5 Instruction on measurement
Notes:
1. After the voltage up to 1000 VDC is measured, it is better to wait for about 2 minutes,
and then conduct the low voltage measurement with the resolution rate 1 to 10 μV.
2. After using the A input terminal for measuring high currents, it is better to wait for about
10 minutes, and then conduct the low-level DC measurements (volts, amps, or ohms) in
order to achieve accuracy. The reason is that measuring the thermal voltage generated by
the high current may cause errors in the low-level measurements.
3. After the completion of all measurements, disconnect the probe and the circuit under
test and remove the probe from the input end of the instrument.
4. When measuring the high voltage and high current, pay special attention to safety.
5. Because MDM8145A / MDM8146A / MDM8155A share the same measurement method,
the measurement will be explained by taking the operation of MDM8155A as an example.

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5.1 Voltage measurement
Notes: Make sure that before the measurements, the terminals are connected
correctly. To avoid damages to the multimeter, do not exceed the rating.
5.1.1 DC voltage measurement
Range: 200mV, 2V, 20V, 200V, 1000V
Input protection: the peak of 1000V for all ranges
Measurement method:
1. Press
DC V
to select DC voltage measurement function; it automatically enters
into DC voltage measurement function every time when the instrument is turned on.
The DC voltage measurement interface is shown in Figure 2.1.1:
DCV
1.99999
AUTO
V
100
%
AUTO 2V
AUTO TRI
Slow Local
Figure 2.1.1 DC Voltage Measurement
Notes: the measured voltage value is shown on the main display, and the value on
the secondary screen represents the ratio of the current measured value and the full
scale.
2. According to Figure 2.1.2, connect the red and black test leads respectively to the
proper input terminalss.
3. Probe the test points and read the display.

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Figure 2.1.2 DCV terminal connection
5.1.2 AC voltage measurement
Note: To ensure accuracy, the input value should be greater than 10% of the range.
Range: 200mV, 2V, 20V, 200V, 750V
AC technology: True RMS measurement
Input protection: RMS of 750V for all ranges.
Measurement method:
1. Press
AC V
to select AC voltage measurement function. The AC voltage
measurement interface is shown in Figure 2.1.3:
ACV
1.99966
AUTO
V
999.996H
z
AUTO 2V
AUTO TRI
Slow Local
Figure 2.1.3 AC Voltage Measurement
Note: the measured voltage value is shown on the main display, and the value on the
secondary screen represents the measured frequency of the current input signal.
2. According to Figure 2.1.4, connect the red and black test leads respectively to the
proper input terminals.
3. Probe the test points and read the display.