Mastech MS850A User Manual

MS850A 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, transistors, 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.
Panel Diagram
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%
General Specifications:
 Maximum Voltage between Input and Ground: CAT III 600V
 Fuse: F200mA/250V, F10A/250V
 Power Supply: 1.5V AAA ×2
1. NCV Sensing Area
2. Display: LCD screen with 31.5 mm character
height
3. NCV Indicator Light
4. Three Buttons (SEL button: function
selection; : flashlight; : press to lock data,
hold down to turn on the backlight).
5. Function/Range Selector Dial
6. Input Jacks
Grounding symbol
Double insulation symbol
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
 Weight: Approximately 300 g (including batteries)
DC Voltage & AC Voltage
Range Resolution
200mV 100uV
2V 1mV
20V 10mV
200V 100mV
600V 1V
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 Resolution
2mA 1uA
20mA 10uA
200mA 100uA
10A 10mA
Overload protection: F200mA/250V fuse; F10A/250V fuse
Frequency range: 40Hz to 1000Hz
Resistance
Range Resolution
200Ω 0.1Ω
2KΩ 1Ω
20KΩ 10Ω
200KΩ 100Ω
2MΩ 1KΩ
200MΩ 100KΩ
Overload protection: 250V DC or AC RMS
Diode and Continuity Test
Range Description
If resistance is less than 50Ω ± 30Ω, the buzzer will sound.
Buzzer
Diode The approximate forward voltage drop is displayed.
Overload protection: 250V DC or AC RMS
Battery Test
Range Display
Value
1.5V 1.5V
3V 3V
9V 9V
Overload protection: 36V DC or AC RMS
Transistor hFE Parameter Test
Range Description
Measures hFE parameter of
hFE
NPN or PNP transistors
DC Voltage AC Voltage
Accuracy Accuracy
±0.5%±3 ±1.0%±10
±0.5%±3 ±1.0%±10
±0.8%±3 ±1.0%±10
±0.8%±3 ±1.0%±10
±0.8%±5 ±1.0%±10
DC Current AC Current
Accuracy Accuracy
±1.0%±5 ±1.8%±5
±1.0%±5 ±1.8%±5
±2.0%±5 ±2.5%±5
±2.5%±5 ±2.5%±10
Display: True RMS
Accuracy
±1.0%±5
±1.0%±5
±1.0%±5
±1.0%±5
±1.0%±5
±5.0%±10
Resolution
0.01V
0.01V
0.01V
Test Condition
Base current approximately
10uA, Vce approximately