Tips for Choosing a Multimeter for Home Use

The multimeter for home use is mainly used for measuring and troubleshooting electrical circuits, electrical devices, electronic circuits, and electronic components. It should have suitable accuracy, stability, reliability, be economical and durable, easy to carry, and reasonably priced. Pocket-sized multimeters such as MF40, MF41, MF30, MF72 can be selected. These multimeters can also measure capacitance, inductance, and the gain β value of transistors. The MF30 model is a highly sensitive multimeter, while the MF72 model is particularly suitable for repairing televisions and tape recorders. Commonly used, highly sensitive multimeters include the 500 model, but it is larger and heavier with high precision. MF15, MF16 models also have relatively high sensitivity and are smaller, making them common multimeters for home use.

Digital multimeters are becoming increasingly popular among electricians due to their high sensitivity, comprehensive functions, intuitive display, good reliability, low power consumption, and compact size. Common models include DT-830. Its range switch can simultaneously complete testing functions and range selection.

When purchasing a multimeter, first observe the casing; it should be smooth and shiny, without scratches or cracks, and the scale on the dial should be clear and clean, without blemishes. Then rotate the range switch; it should be light and flexible, with no jamming or noise. Shake the multimeter horizontally a few times; the pointer should have good damping, and its swing should not be too large, with no knocking sounds inside the meter. Check the mechanical zero (the calibrator in the center position); see if the pointer can pass zero and accurately adjust to the zero point. Finally, check the battery on the multimeter in the ohm range: short the two probes, rotate the zeroing potentiometer in both directions, and the pointer should swing back and forth at “0” Ω, accurately adjusting to zero. If possible, check the product performance according to the manual to see if it meets the specified technical requirements.

Improper use of a multimeter can bend the pointer or even burn out the meter head. To prevent such accidents, pay attention to the following points when using a multimeter:

1) Before each measurement, estimate the size of the value to be measured and set the range switch to the appropriate range. If you are unsure about the size, first set the range to the maximum range, then approach the appropriate range. Measuring a large value with a small range may bend the pointer.

2) When measuring resistance, the circuit being measured must be disconnected from the power supply.

3) When testing high voltage or large current, do not rotate the range switch. Otherwise, it will cause arcing at the contacts, damaging the switch.

4) When measuring electrolytic capacitors, they must be short-circuited and discharged first before measurement.

5) To prevent the meter head from burning out during incorrect use, two silicon diodes can be connected in parallel across the meter head (one in forward parallel and one in reverse parallel). Since the conduction voltage of silicon diodes is generally greater than 0.5V, the forward resistance of the diodes is very high below 0.5V, having minimal impact on the original internal resistance of the meter head, which can be ignored. When an incorrect measurement occurs, the rising voltage will lower the forward resistance of the silicon diodes, diverting most of the current through the diodes, thus protecting the meter head.

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Excerpt from 350 Questions on Home Electrical Renovation

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