Pointer type MF47 type multimeter instruction manual

First, the basic function of MF47 multimeter

MF47 is a novel design of magnetoelectric rectification portable multi-range universal meter. It can be used for side current DC current, AC and DC voltage, DC resistance, etc. It has 26 basic ranges and levels, capacitance, inductance, and transistor DC parameters. Wait for 7 additional reference ranges.

Second, the dial and the gear plate

The dial and the gear plate are printed in red, green and black. The color of the dial is AC red, the transistor is green, and the rest is made of black. The reading is convenient. The dial has six scales. The first one is for testing. For the resistance; the second is for measuring AC and DC voltage, DC current; the third is for measuring transistor amplification; the fourth is for measuring capacitance; the fifth is for measuring inductance; Audio level. A mirror is mounted on the dial to eliminate parallax.

Except that the AC 2500V and DC 5A have separate sockets, the other files only need to rotate one selector switch, which is convenient to use.

Third, the method of use

Before use, check whether the pointer refers to the mechanical zero position. If it does not mean that it is at the zero position, the zero adjuster that can rotate the cover makes the pointer indicate the zero position.

Insert the red and black plugs of the test rod into the "+" "-" socket. For example, when measuring AC 2500V or DC 5A, the red plug should be plugged into the socket labeled 2500 or "5A".

1, DC current measurement

When measuring 0.05~500mA, turn the switch to the required current level. When measuring 5A, the rotary switch can be placed on the 500mA DC current limit and then the test rod is connected in series to the circuit under test.

2, AC and DC voltage measurement

When measuring AC 10~1000V or DC 0.25~1000V, turn the switch to the required voltage level. When measuring AC/DC 2500V, the switch should be rotated to the AC 1000V or DC 1000V position respectively, and then the test rod is connected to the circuit under test. end.

3, DC resistance measurement

Install the battery (R14 type 2#1.5V and 6F22 type 9V each). Turn the switch to the required resistance file, short the test rod ends, adjust the zero ohm adjustment knob to make the pointer align with ohm "0 "In position, (if the ohmic zero is not indicated, the battery voltage is insufficient, the battery should be replaced), and then the test rod is connected across the two ends of the circuit under test for measurement.

When measuring the resistance accurately, you should select the appropriate resistance gear position so that the pointer can point to the middle third of the table dial as much as possible.

When measuring the resistance in the circuit, the circuit power should be cut off first. If there is a capacitor in the circuit, it should be discharged first.

When checking the leakage resistance of the electrolytic capacitor, the switch can be turned to R × 1K, the red rod of the test rod must be connected to the negative pole of the capacitor, and the black rod is connected to the positive pole of the capacitor.

4, audio level measurement

In a certain load impedance, used to measure the gain of the amplifier and the loss of line transmission. The unit of measurement is expressed in decibels.

The relationship between audio level and power voltage is:

NdB=10log10P2/P1 =20log10V2/V1

The scale factor of the audio level is designed according to the 0dB=1mW600Ω conveyor line standard.

That is, V1=(PZ)1/2=(0.001*600)1/2=0.775V

P2V2 is the measured power or measured voltage

The audio level is based on AC 10V. If the indication value is greater than +22 dB, it can be measured at various limits above 50V. The indication value can be corrected by the value shown in the table below.

Measure limit

Increase value by level scale

Level measurement range

10V

-10~+22 dB

50V

14 dB

+4~+36 dB

250V

28 dB

+18~+50 dB

500V

34 dB

+24~+56 dB

The measurement method is basically similar to the AC voltage. Rotate the switch to the corresponding AC voltage file and make the pointer have a large deflection. If the DC voltage component is included in the circuit under test, a 0.1μf can be connected in series in the "+" socket. Isolation capacitors.

5, capacitance measurement

Turn the switch to the AC 10V position, the measured capacitor is connected in series to any test rod, and then connected to the 10V AC voltage circuit for measurement.

6, inductance measurement

Same as the capacitance measurement method.

7, transistor DC parameter measurement

(1) Measurement of DC amplification factor hFE

First turn the switch to the transistor to adjust the ADJ position, short the red and black test bars, adjust the ohmic potentiometer, align the pointer with the 300hFE mark line, then turn the switch to the hFE position, and insert the transistor pins to be tested into the transistor test socket. In the ebc socket, the value indicated by the pointer deflection is approximately the DC amplification value of the transistor. The N-type transistor should be inserted into the N-type tube hole, and the P-type transistor should be inserted into the P-type tube hole.

(2) Reverse cutoff current Iceo, Icbo measurement

Iceo is the reverse cut-off current between the collector and the emitter (base open). Icbo is the reverse cut-off current between the collector and the base (open emitter). The rotary switch Ω×1K stops the test rod at both ends. Adjust the zero ohms (at this time, the full-scale current value is about 90uA). Separate the test rod, and then insert the transistor to be tested into the socket. At this time, the value of the pointer is about the reverse cut-off current value of the transistor. Multiplying the value by 1.2 is the actual value.

When the value of the Iceo current is greater than 90μA, it can be measured with Ω×100 steps (the full-scale current value is about 900μA).

The N-type transistor should be inserted into the N-type header, and the P-type transistor should be inserted into the P-type holder.

(3) Discrimination of the polarity of the triode pins (put the multimeter in Ω×1K)

1 Determine the base b. Since b to c - b to e are two PN junctions respectively, its reverse resistance is large, and the forward resistance is very small. The transistor can be arbitrarily taken as a base at the time of testing. Connect the red test bar to the "base" and the black test bar to the other two pins. When the measured values ​​are low resistance, the pin touched by the red test bar is the base b and is P. Type tube, (if measured by the above method, it is a high resistance value, then it is an N-type tube). If the resistance of the two pins is very different when measuring, another one can be selected as the assumed base until it is satisfied. Until the above conditions.

2 determine the collector c. For the PNP-type triode, when the collector is connected to a negative voltage, the emitter is connected to a positive voltage, the current amplification factor is relatively large, while the NPN-type tube is the opposite. The test assumes that the red test rod is connected to the collector c, The black test bar is connected to the emitter e, the resistance value is recorded, and then the red and black test bar exchange test, the measured resistance value is compared with the first resistance value, and the red test bar with small resistance value is connected to the collector c The black is the emitter e, and it can be judged to be a P-tube (the N-tube is the opposite).

(4) Diode polarity discrimination

When testing, R×10K file is selected, and one end of the black test bar is measured to have an extremely positive resistance.

The multimeter is in the ohmic circuit, the red test bar is the battery negative, and the black is the battery positive.

Note: The test methods described above generally use R×100, R×1K files. If R×10K files are used, the PN junction of the measured triode may be broken down due to the higher voltage supply of 15V. If measured with R × 1 file, the current will be damaged due to excessive current (about 90mA).

Fourth, technical specifications

Range of limits

Sensitivity and

Voltage drop

Precision

Error degree

DC

Current

0-0.05mA-0.5mA-5mA--50mA

-500 mA-5A

0.3V

2.5

Above the limit

Percentage calculation

DC

Voltage

0-0.25V-1V-2.5V-10V-50V

-250V-500V-1000V

-2500V

20KΩ/V

2.5

5

Above the limit

Percentage calculation

communicate with

Voltage

0-10V-50V-250V (45-65-500Hz)

-500V-1000V-2500V (45-65Hz)

4KΩ/V

5

Above the limit

Percentage calculation

DC

resistance

R × 1, R × 10, R × 100, R × 1K,

R×10K

R×1 center scale is 16.5Ω

2.5

Calculated as a percentage of the arc length of the scale

10

Indicating value

Percentage calculation

Audio

Level

-10d B~+22 d B

0dB=1mw 600Ω

hFE

0~300hFE

Transistor DC amplification

inductance

20~1000H

capacitance

0.001~0.3uf

Five, matters needing attention

1. Although the multimeter has dual protection devices, the following procedures should be followed to avoid accidental loss.

(1) When measuring high voltage or high current, in order to avoid burning out the switch, the quantity limit should be changed when the power is cut off.

(2) When measuring the unknown voltage or current, you should first select the highest number. After reading the value for the first time, you can gradually turn to the appropriate position to obtain the accurate reading and avoid burning the circuit.

(3) When the fuse is accidentally broken due to overload, the watch case can be opened and replaced with the same type of fuse (0.5A/250V).

2. When measuring high pressure, stand on the dry insulation board and operate with one hand to prevent accidents.

3. The dry batteries of various resistances should be inspected regularly and replaced to ensure the measurement accuracy. In general, the multi-meter should not be used to switch the gear plate to the AC 250V; if it is not used for a long time, the battery should be removed to prevent the electro-hydraulic corrosion and damage other parts.

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