Routine Operation and Maintenance Guidelines for Digital Multimeters
First, turn on the digital multimeter. Then select the quantity to be measured: voltage, current, resistance, or other parameters. Next, choose the appropriate range. If the parameter value is unknown, start with the highest range and gradually lower it. Before measurement, check that the test leads are inserted into the correct terminals. When turning the range selector, apply moderate force to avoid damaging the internal metal contacts. After use, always set the function and range selector to a high-voltage range.
2. Notes on Digital Multimeter Measurements
(1) It is normal for resistance measurements on high-resistance ranges to differ from those obtained with an analog multimeter, mainly due to slightly different test conditions.
(2) When measuring polarized quantities, the displayed polarity corresponds to the probe connections. When no polarity is shown, the red probe is at the higher potential or is the current input terminal. When a "-" polarity is displayed, the red probe is at the lower potential or is the current output terminal.
(3) Resistance and diode test modes differ from those of analog multimeters.On an analog multimeter, the polarities of the red and black probes are reversed relative to the internal battery: the black probe is positive, and the red probe is negative.On a digital multimeter, the probe polarities match the internal source: the red probe is positive, and the black probe is negative, consistent with voltage and current measurement modes. This design avoids confusion and is superior to analog multimeters.
(4) For transistors with unknown polarity or pin arrangement, use the hFE transistor test socket and repeat measurements with different pin combinations to identify the emitter, base, and collector.
(5) CalibrationDigital multimeters should be calibrated periodically. Use a similar or higher-precision digital meter for calibration, following the sequence:first DC ranges, then AC ranges, and finally capacitance ranges.
Digital multimeters typically use a 9V battery, which usually needs replacement after several months. It is recommended to use a rechargeable 9V battery instead, such as the NiCd model GP‑15F8K, which is fully compatible with standard 9V batteries.
