Mastech M839b User manual

POCKET-SIZED

DIGITAL MULTIMETER

OPERATOR’S

INSTRUCTION MANUAL

F250mA250V

SAFETY INFORMATION

The meter has been designed according to IEC1010 concerning

electronic measuring instruments with an overvoltage category (CATII)

and pollution 2.

Follow all safety and operating instructions to ensure the meter is used

safely and is kept in good condition.

Full compliance with safety standards can be guaranteed only with test

leads supplied. If necessary, they must be replaced with the type specified

in this manual.

DURING USE

•

Never exceed the protection limit indicated in the specifications for

each range of measurement.

When the meter is linked to measurement circuit, be careful not to

touch unused terminals.

Never use the meter to measure voltages that might exceed 600V

above earth groud in category II installations.

Always be careful when working with voltages above 60V dc or

30V ac rms. Keep fingers behind the probe barriers while

measuring.

Before attempting to insert transistors for testing, always be sure

that test leads have been disconnected from any measurement

circuits.

Components should not be connected to the hFE socket when

making voltage measurements with test leads.

Do not perform resistance measurements on live circuits.

SAFETY SYMBOLS

Important safety information, refer to the instruction manual.

Dangerous voltage may be present.

Earth ground.

Indicates compliance with requirements for double insulation

Fuse must be replaced with ratings specified in the

manual.

MAINTENANCE

•

Before opening the case, always disconnect test leads from all

energized circuits.

For continuous protection against fire, replace fuse only with

ratings: F 250mA/250V (Quick Acting).

•

Never use the meter unless the back cover is in place and

fastened completely.

Do not use abrasives or solvents on the meter. To clean

it using only a damp cloth and mild detergent.

FRONT PANEL DESCRIPTION

1 Rotary Switch

This switch is used to select the function and desired ranges as

well as to turn on/off the meter.

2Display

3 1/2 digit, 7 segment, 0.5″high LCD.

3 “COM” Jack

Plug in connection for black (negative) test lead.

4 “VΩmA” Jack

Plug in connection for red (positive) test lead for voltage, resistance

and current (except 10A) measurements.

5 “10A” Jack

Plug in connection for red (positive) test lead for 10A

measurement.

SPECIFICATIONS

Accuracy is guaranteed for 1 year, 23℃±5℃, less than 75%relative

humidity.

AC VOLTAGE

Range Resolution Accuracy

200V 100mV ±1.2 % of rdg ±10 digits

600V 1V ±1.2 % of rdg ±10 digits

Overload protection: 600V dc or rms ac for all ranges.

Frequency range: 45Hz to 450Hz

Response: Average responding, calibrated in rms of a sine wave.

DC VOLTAGE

Range Resolution Accuracy

200mV 0.1mV ±0.5% of rdg ±2 digits

2000mV 1mV ±0.5% of rdg ±2 digits

20V 10mV ±0.5% of rdg ±2 digits

200V 100mV ±0.5% of rdg ±2 digits

600V 1V ±0.8% of rdg ±2 digits

Overload protection: 250V rms. ac for 200mV range and 600V dc or rms

ac for other ranges.

DC CURRENT

Range Resolution Accuracy

200μA 0.1μA ±1.0% of rdg ±2 digits

2000μA 1μA ±1.0% of rdg ±2 digits

20mA 0.01mA ±1.0% of rdg ±2 digits

200mA 0.1mA ±1.5% of rdg ±2 digits

10A 10mA ±3.0% of rdg ±2 digits

Overload protection: F250mA 250V fuse (10A range unfused).

RESISTANCE

Range Resolution Accuracy

200Ω0.1Ω±0.8% of rdg ±3 digits

2000Ω1Ω±0.8% of rdg ±2 digits

20kΩ10Ω±0.8% of rdg ±2 digits

200kΩ100Ω±0.8% of rdg ±2 digits

2000kΩ1kΩ±1.0% of rdg ±2 digits

Maximum open circuit voltage: 3.2V

Overload protection:250V rms. ac on all ranges.

DIODE TEST

Range Description

Show the approx. forward voltage drop of the diode.

Overload protection: 250V rms. ac.

GENERAL

Maximum voltage between

terminals and earth ground : CAT II 600V

Fuse protection : F 250mA/250V, 10A range

unfuse.

Power supply : 1 ×9V , 6F22 or NEDA 1604

Display : LCD, 1999 counts,

updates 2-3/ sec.

Measuring method : Dual-slope integration A / D

converter

Overrange Indication : Only figure “1” on the display

Polarity indication : “-”displayed for negative polarity

Operating Environment : 0 to 40℃(32°F to 104°F)

Storage temperature : −10℃to 50℃(10°F to 122°F).

Low battery indication : “BAT” appear on the display

Size : 126×70×25mm

Weight : Approx. 170g

OPERATING INSTRUCTIONS

AC VOLTAGE MEASUREMENT

1. Connect the red test lead to “VΩmA” jack and the black lead to the

“COM” jack.

2. Set the rotary switch at desired V~ position.

3. Connect test leads across the source or load being measured and read

voltage value on the LCD display.

DC VOLTAGE MEASUREMENT

1. Connect red test lead to “VΩmA” jack and the black test lead to the

“COM” jack.

2. Set rotary switch at desired V position. If the voltage to

be measured is not known beforehand, set range switch at the highest

range position and then reduce it until satisfactory

resolution is obtained.

3. Connect test lead across the source or load being measured. Read

voltage value on the LCD display along with the polarity of the red lead

connection.

DC CURRENT MEASUREMENT

1. Connect the red test lead to the “VΩmA” jack and the black lead to

“COM” jack. (For measuring current between 200mA and 10A, remove

red lead to “10A” jack.)

2. Set the rotary switch at desired A position.

3. Open the circuit in which the current is to be measured, and connect

test leads in series with the circuit.

4. Read current value on the LCD display along with the polarity of red

lead connection.

RESISTANCE MEASUREMENT

1. Connect the red test lead to “VΩmA” jack and the black lead to “COM”

jack. (The polarity of red lead is positive “+”)

2. Set the rotary switch at desired Ωrange position.

3. Connect test leads across the resistance to be measured and read

LCD display.

4. If the resistor being measured is connected to a circuit, turn off power

and discharge all capacitors before applying test leads.

TRANSISTOR TEST

1. Set the rotary switch at “hFE” position.

2. Determine whether the transistor under testing is NPN or PNP type and

locate the emitter, base and collector leads. Insert the leads into proper

holes of the hFE socket on the front panel.

3. The meter will show the approximate hFE value at the condition of base

current 10μA and Vce 3V.

NOTE:

Before attempting to insert transistors for testing, always be sure that test

leads have been disconnected from any measurement circuits.

Components should not be connected to the hFE socket when making

voltage measurements with test leads.

DIODE TEST

1. Connect the red test lead to “VΩmA” jack and the black lead to “COM”

jack. (The polarity of red lead is positive “+”).

2. Set the rotary switch at position.

3. Connect the red lead to the anode of the diode to be tested and the

black lead to the cathode of the diode.

4. The approx. forward voltage drop of the diode will be display in mV. If

the connection is reversed, only figure “1” will be shown.

BATTERY & FUSE REPLACEMENT

If the sign “BAT” appears on the LCD display, it indicates that the battery

should be replaced. Loosen screws on the back cover and open the case.

Replace the exhausted with a new one of the same type.

Fuse really need replacement and blow almost always as a result of

operator’s error. Open the case and replace the blown fuse with the

ratings specified: F250mA/250V.

WARNING

Before attempting to open the case, always be sure that test leads have

been disconnected from measurement circuits. Close case and tighten

screws completely before using the meter to avoid electrical shock

hazard.

ACCESSORIES

•Operator’s instruction manual

•Set of test leads

•Battery: 1 ×9V 6F22 or NEDA 1604 type

CAUTION:

Using this appliance in an environment with a strong radiated

radio-frequency electromagnetic field (approximately 3V/m), may

influence its measuring accuracy. The measuring result can be strongly

deviating from the actual value.

HYS004369

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