Digital multimeters are widely used in electrical inspection and equipment commissioning. According to chilok industry data, 76% measurement errors are caused by external interference instead of internal instrument damage. This article formulates on-site calibration standards based on JJG 124-2021 to solve reading jitter and value deviation faults.
1. Ambient temperature drift: Heat radiation from inverters causes sampling resistance offset, bringing ±1.3% DC voltage deviation;
2. Probe attenuation: Repeated bending and oil corrosion damage probe shielding layer, resulting in AC reading jitter;
3. Sampling component aging: Long-term full-range overload leads to capacitance attenuation and zero drift;
4. Grounding interference: Equipotential difference causes background noise for weak current measurement.
1. Zero-point calibration: Short-circuit probes under DC mV gear, reset manually if base drift exceeds 0.03mV;
2. Probe conductivity inspection: Bend probe root repeatedly, replace probe if intermittent beep occurs;
3. Anti-interference operation: Install grounding clip and insulating pad to cut off stray coupling;
4. Range restriction: Avoid low-voltage signal measurement under 750V AC gear to prevent divider resistance aging.
Quality-control multimeters shall be calibrated every 6 months; daily maintenance instruments shall be verified once a year. Re-calibration is mandatory after water ingress and overload damage.