# How to use a mechanical multimeter?

Last Update Time: 2019-01-27 14:43:12

1. Before using the mechanical multimeter, you should pay attention to whether the needle refers to the position of “∞ (infinity)”. If the needle is not in this position, apply the screw driver to adjust the mechanical zero button, so that the needle is in the infinite position. Note: This zero adjustment button can only be adjusted half a circle, otherwise it may be damaged, so that it cannot be adjusted.

2. Before measuring, first determine the physical quantity of the test, and set the transfer switch to the corresponding gear, and also consider the connection of the test leads. Then test again to avoid damage to the multimeter due to misuse.

3. For general measurement, insert the red test pen (positive) into the "+" hole and the black test pen (negative) into the "-" or "*" hole. To measure high current and high voltage, you can insert the red test pen into the 2500V or 5A jacks.

4. Measuring resistance: Before using different ranges of resistance, the positive and negative test leads should be docked first, adjust the “zeroing potentiometer Ω”, let the hands just point to the zero position, and then measure again, otherwise the measured resistance value The error is too large.

Note: Every time you change the gear, you must perform a zero adjustment, and then connect the test leads to the two ends of the measured object to measure the resistance value.

The reading of the resistance value: multiplying the number indicated by the switch by the reading on the dial is the resistance of the measured resistance. For example: measure a resistor with R × 100, the pin refers to the position of “10”, then the resistance of this resistor is 10×100Ω =1kΩ; if the needle refers to the position of “1”, its resistance value is 100Ω. If it is at "100", it is 10kΩ, and so on.

5. Measure voltage: When measuring voltage, the multimeter should be adjusted to the voltage block, and the two test leads should be connected in parallel in the circuit for measurement. When measuring AC voltage, the test pen can be divided into positive and negative poles; when measuring DC voltage, the red test lead is connected to the power supply. The positive pole, the black test lead is connected to the negative pole of the power supply. If it is reversed, the needle will swing in the opposite direction. If the voltage of the circuit under test cannot be estimated before measurement, apply a larger range to test. If the needle swing is small, then switch the switch to a smaller range; if the needle is quickly placed at zero, it should be Immediately remove the test leads from the circuit, add a large amount of time and then measure.

Note: When measuring the voltage, observe the swing of the hands while trying to measure with the test leads to prevent the voltage from being too high to bend the needle or burn the multimeter.

6. Measure DC current: measure the test leads in the circuit (disconnect the circuit). The red pen is connected to the positive pole of the circuit, and the test pen is connected to the negative pole in the circuit. When measuring, you should use the high gear first. If the needle swings very little, then change the low gear. To measure large currents, an extension should be used.

Note: The current block of the multimeter is the most easily burned, so be careful when measuring.

7. Transistor amplification factor (hFE) measurement: first turn the transfer switch to ADJ block (the multimeter without ADJ gear can use R × 1k block), adjust the zero position, and then transfer the transfer switch to hFE for measurement. Insert the b/c/e three poles of the transistor into the three jacks of b/c/e on the multimeter, insert the PNP transistor into the PNP position, and read the value of the NPN transistor on the fourth scale line into the NPN position , read the value of the 5th tick mark. Both are read by real numbers.

8. Measurement of penetration current. According to the "Measurement of Transistor Magnification (hFE)" method, the transistor is inserted into the corresponding hole, but the "b" pole of the transistor is not inserted. At this time, the needle will have a small swing, which is estimated according to the size of the needle swing. The size of the penetration current, the greater the amplitude of the needle swing, the greater the punch-through current, and vice versa.

Since the multimeter CUF, LUH scale line are rarely applied, they are not described here. See the instructions for use.

The mechanical multimeter structure can refer to the following article:

What is the structure of a common mechanical multimeter?