Key points for using pointer multimeter
The pointer type (also known as analog type) multimeter has a development history of nearly a hundred years. Due to its complete functions, simple operation, easy portability, low price, and easy maintenance, it has long been a necessary instrument for electronic measurement and maintenance work. Below are several key points for using a pointer multimeter.
Before using a multimeter, one should be familiar with the functions of each conversion switch knob, dedicated socket, measuring socket, and instrument accessory, and understand the corresponding measurement of each scale line. Every time you pick up the probe to prepare for measurement, be sure to check if the measurement type and range selection switch are in the correct position.
1) A pointer multimeter should generally be placed horizontally when in use, otherwise it may cause tilt errors. It is found that the pointer does not point to the mechanical zero point. The screw under the meter head needs to be adjusted to return the pointer to zero and eliminate the zero point error.
2) The multimeter should be used and stored in a dry, vibration free, strong magnetic field free, and suitable temperature environment. A humid environment can reduce the insulation strength of instruments and damage the components inside the instrument due to moisture. Mechanical vibration and impact can demagnetize the magnetic steel of the meter head, resulting in a decrease in sensitivity. When used near strong magnetic fields, measurement errors will increase. If the ambient temperature is too high or too low, it can cause changes in the forward and reverse resistance of the rectifier component, alter the rectification coefficient, affect the sensitivity of the meter head, and the resistance values of the shunt resistor and voltage divider resistor, leading to temperature errors.
3) After the measurement is completed, the range selection switch should be set to the highest voltage level to prevent accidental burning of the meter next time. Some multimeters (500 type) have a neutral position, or after using the "OFF" gear, the switch knob should be turned to the appropriate position to short-circuit the measuring mechanism internally.
4) If the DC voltage range is mistakenly used to measure AC voltage, the meter needle will not move or shake slightly; If the AC voltage range is mistakenly used to measure the DC voltage, the reading may be twice as high or zero, depending on the specific connection of the multimeter.
5) The basic error of the voltage range is expressed as a percentage of the full scale, so the closer the measured value is to the full scale value, the smaller the error. Generally speaking, the selected range should be able to deflect the pointer by more than 1/3 to 1/2.
6) When measuring the voltage of the internal resistance power supply, it is advisable to choose a higher voltage range as much as possible to increase the internal resistance of the voltage range. This reduces the deflection angle of the pointer, but the measurement results obtained can better reflect the real situation. Nevertheless, significant measurement errors may still occur.
7) Due to the nonlinearity of rectifier components, the error of measuring AC voltage below 1V with a multimeter will also increase. Therefore, many multimeters no longer scale AC voltage below 1V.
8) A multimeter cannot directly measure non sinusoidal voltages such as square waves, rectangular waves, triangular waves, sawtooth waves, trapezoidal waves, etc. Because the AC voltage range of the multimeter actually measures the average value of the rectified AC voltage, while the scale is calibrated based on the effective value of the sinusoidal AC voltage. If the measured voltage is not a sine wave, the relationship between its average value and effective value will change, so it cannot be directly read.
