What Is Involved in Multimeter Calibration?

Basic electronic circuit measurement tool. Can be used for multiple electrical applications.

Analog multimeter

Analog multimeter is an instrument used to measure DC current, DC voltage and AC current, AC voltage, and resistance. It is mainly composed of three parts: indicating part, measuring circuit and conversion device. Compared with digital multimeter, it is convenient and intuitive.

The analog multimeter is composed of a meter head, a measuring circuit and a transfer switch.

There are generally four tick marks on the head of an analog multimeter, which represent resistance, voltage / current, and level readings.

The calibration of each file of the ohmmeter is based on the central resistance value. Therefore, when measuring the resistance, the pointer should be shown as close to the center of the scale as possible to reduce the error. The calibration of each file of the ammeter and voltmeter is performed according to their respective full-scale values. Therefore, the pointer should be displayed as close to the full-scale value as possible to reduce the error.

Level measurement is actually achieved by AC voltage measurement. Therefore, although the level is defined by taking the logarithm of the power ratio, it can be converted into a voltage measurement. Since the zero power level is the level when lmW power is obtained on a 600W load, then the voltage at the load at zero power level, this voltage value is the zero level voltage, so the voltage (absolute) level: where Vx is The voltage value at a point in V.

The decibel scale on the dial corresponds to the lowest range of the AC voltage (10V range).

The basic working principle of the electromagnetic meter head is to first convert the measured analog power into a current signal through a certain measuring mechanism, and then the current signal is used to drive the pointer of the electromagnetic meter head to deflect. Measured size.

I. Preparation

The multimeter should be placed horizontally; adjust the "mechanical zero" screw so that the pointer indicates the zero position; insert the red test lead into the "+" jack and the black test lead into the "-" jack.

Second, the measurement of resistance

1. Select W file correctly.

2. Ohm zeroing: Before the resistance measurement, first short-circuit the two test leads, the pointer will deflect towards the full scale; then adjust the ohmic zeroing potentiometer so that the pointer is on the 0W scale.

3. Measure the resistance value: Connect the two test leads to the two ends of the resistance to be measured respectively. The resistance value = W-fold magnification × the reading of the pointer on the scale.

Third, the measurement of DC current

1. Select the DC current range of the transfer switch.

2. Connect the measurement circuit: The multimeter is connected in series to the circuit under test. The red test lead is connected to the current inflow direction, and the black test lead is connected to the current outflow direction.

3. Reading: The DC current value is equal to the pointer value of the corresponding scale line of the DC current range.

Fourth, the measurement of DC voltage

1. Select the DC voltage range of the transfer switch.

2. Connect the measurement circuit: the red test lead is connected to the positive end of the measured DC voltage, and the black test lead is connected to the negative end of the measured voltage.

3. Reading: The DC voltage value is equal to the pointer value of the corresponding scale line of the DC voltage file.

V. Measurement of AC voltage

1. Select the AC voltage range of the transfer switch.

2. Two test pens are connected at both ends of the AC voltage to be measured, regardless of polarity.

3. Reading: The AC voltage value is equal to the pointer value of the corresponding scale line of the AC voltage range.

Measurement of AC current

1. Select the AC current range of the transfer switch.

2. Connect the multimeter in series to the circuit under test. The polarity of the two test leads need not be considered.

3. Reading: The AC current value is equal to the pointer value of the corresponding scale line of the AC current range.