Daily Maintenance of Digital Multimeter Calibrator
The digital multimeter calibrator is used to verify multimeters and various meter heads of Class 1 and below.
Improper operation may damage the meter under test and the internal circuits of the instrument. Therefore, careful testing is required during use to extend the service life of the instrument.
① This instrument operates in an ambient temperature range of 0°C to 40°C with relative humidity below 80%. The input power supply should preferably be stabilized. Otherwise, fluctuations, overvoltage or undervoltage of the external power supply, even near the upper and lower operating limits, may damage the instrument's power circuit.
② Switch on the power supply and warm up the instrument for 30 minutes. Turn the two output adjustment knobs counterclockwise to the minimum position first. Set the function selector switch, range switch and frequency switch (400 Hz for DC ranges) to required positions according to the type and range of the meter under test. Press the "Output" button; the red indicator lamp lights up. Slowly turn the "Coarse Adjustment" knob clockwise to carry out output verification.
③ After completing the verification of each range or item, turn the "Coarse Adjustment" and "Fine Adjustment" knobs counterclockwise to the minimum position before switching to another range or item. This prevents damage to the meter under test or the instrument's output circuit caused by excessive output voltage or current.
④ Never short the output wires in any voltage range, and never leave the output wires open-circuited in any current range, otherwise the instrument will be damaged.
⑤ Do not operate beyond the instrument's rated range. For example, do not apply 5.5 V on the 5 V range.
⑥ During verification, if the current range circuit of the meter under test is open-circuited, adjusting the current "Coarse Adjustment" will produce no response on both the meter under test and the instrument display. Do not turn the knob further to avoid damaging the instrument. Under heavy load conditions, if slowly increasing the "Coarse Adjustment" results in little change in readings on both meters, stop the verification immediately.
⑦ Avoid full-scale output for the 7.5 A and 10 A ranges. Do not keep output near the upper limit for a long time, as this may easily damage the instrument.
