Mastech MS850B User Manual

MS850B Digital Multimeter User Manual
This product is a small handheld digital multimeter offering stable
performance, high reliability, and anti-drop capabilities. The instrument features an
LCD screen with 31.5 mm character height for clear readings. The circuit design
centers around a large-scale dual-slope integrating A/D converter with overload
protection, making this a superior and compact measurement tool.
The instrument can measure AC/DC voltage, AC/DC current, resistance,
diodes, and circuit continuity. It also functions as a battery tester, live wire detector,
and non-contact voltage (NCV) tester. The device is equipped with a backlight and
a flashlight feature, allowing users to read measurements in low light and
illuminate dark environments.
Safety Information
This series of digital multimeters has been designed in accordance with
IEC1010 600V (CAT III) and Pollution Degree 2 standards. Please read this user
manual thoroughly to ensure safe instrument use and measurement accuracy.
Safety Symbols
Important safety symbol
High voltage symbol
Operating Precautions
⚫ To comply with safety standards, the instrument must be used with the provided
test leads only. If the test leads are damaged, they must be replaced with the
same model or with leads that have the same electrical specifications.
⚫ Do not exceed the input limit specified for each range.
⚫ Avoid touching unused input terminals during measurement.
⚫ When the range of the value to be measured is unknown, set the function/range
dial to the highest range.
⚫ Before adjusting the function/range dial, ensure that the test leads are
disconnected from the circuit being tested.
⚫ Before measuring resistance in a live circuit, ensure that all power sources are
turned off and all capacitors are fully discharged.
⚫ Be cautious when measuring voltages above 60V DC or 30V AC. Do not touch
the parts of the test leads beyond the finger guards.
⚫ When measuring televisions or switch-mode power supplies, be aware that
pulses in the circuit may damage the instrument.
⚫ Before testing transistors, ensure that the test leads are not connected to any
circuit.
⚫ Before using the test leads to measure voltage, ensure that no electronic
components are connected to the transistor test socket.
Maintenance
⚫ Disconnect the test leads from the circuit before opening the back cover.
⚫ To protect the instrument's internal circuitry, always replace the fuse with one of
the same specifications.
⚫ Do not use the instrument if the back cover is not securely closed or if the
screws are not tightened.
⚫ Clean the instrument with a damp cloth and a small amount of detergent only.
Do not use chemical solvents on the casing.
⚫ If any abnormalities are observed, immediately discontinue use and send the
instrument for repairs.
Technical Specifications
Accuracy: ±(percent of reading + number of counts), valid for 1 year
Environmental temperature: 18°C to 28°C. Environmental humidity: ≤80%
Panel Diagram
1．NCV Sensing Area
2．Display: LCD screen with
character height
3．NCV Indicator Light
4． Button: Press to switch between MAX
and MIN values, hold down to exit MAX/MIN
value retention or relative
measurement; : Flashlight button;
to lock data, hold down to turn on the backlight.
5. Function/Range Selector Dial
6. Input Jacks
Grounding symbol
Double insulation symbol
General Specifications:
 Maximum Voltage between Input and Ground: CAT III 600V
 Fuse: F200mA/250V, F10A/250V
 Power Supply: 1.5V AAA ×2
Auto Power Off: The instrument will automatically power off after
approximately 15 minutes.
 Maximum Display Value: 1999
 Overload Indicator: "OL"
 Polarity Display: Negative polarity is displayed as "-"
 Working Temperature: 0°C to 40°C
 Storage Temperature: -10°C to 50°C
 Low Battery Indicator: The display shows
 Dimensions: 150 mm × 75 mm × 47 mm
31.5 mm
 Weight: Approximately 300 g (including batteries)
DC Voltage & AC Voltage
Range
20mV
value (REL)
200mV
: press
2V
20V
200V
600V
Input impedance: 10MΩ
Overload protection: 200mV range: 250V DC or AC RMS; all other ranges:
600V DC or AC RMS
AC voltage frequency range: 40Hz to 1000Hz Display: True RMS
DC Current & AC Current
Range
200uA
2000uA
20mA
200mA
2A
10A
Overload protection: F200mA/250V fuse; F10A/250V fuse
Frequency range: 40Hz to 1000Hz
Resistance
Range
200Ω
2KΩ
20KΩ
200KΩ
2MΩ
20MΩ
Overload protection: 250V DC or AC RMS
Diode and Continuity Test
Range
Buzzer
Diode
Overload protection: 250V DC or AC RMS
Temperature Measurement
Function
℃
Resolution DC Voltage
Accuracy
10uV ±1.0%±5
100uV ±0.5%±3
1mV ±0.5%±3
10mV ±0.8%±3
100mV ±0.8%±3
1V ±0.8%±5
Resolution DC Current
Accuracy
0.1uA ±1.0%±5
1uA ±1.0%±5
10uA ±1.0%±5
100uA ±2.0%±5
1mA ±2.5%±5
10mA ±2.5%±5
Display: True RMS
Resolution Accuracy
0.1Ω
±1.0%±5
1Ω
±1.0%±5
10Ω
±1.0%±5
100Ω
±1.0%±5
1KΩ
±1.0%±5
10KΩ
±1.2%±8
Description
If resistance is less than 50Ω ± 30Ω, the buzzer will sound.
The approximate forward voltage drop is displayed.
Range Resolution
-20℃ to 0℃
1℃
AC Voltage
Accuracy
±1.0%±10
±1.0%±10
±1.0%±10
±1.0%±10
±1.0%±10
±1.0%±10
AC Current
Accuracy
±1.8%±5
±1.8%±5
±1.8%±5
±2.5%±5
±2.5%±10
±2.5%±10
Accuracy
±4℃