Time Relay Accuracy Measurement Method
Accurate time relay measurement requires systematic steps to ensure reliable results. Before measurement, confirm the relay model, rated parameters, and operating environment, maintaining ambient temperature at 20±5°C and humidity below 85%RH. Prepare a high-precision timer (resolution 0.001s), regulated power supply (±1% fluctuation), standard load (matching contact rating), and digital multimeter.
Calibrate the timer and power supply, ensuring equipment error is within ±0.5%. Mount the relay on an insulated workbench and use a four-wire connection for control and measurement circuits to minimize contact resistance interference. Set target delay times—such as 5s, 30s, 60s—as test points. Apply rated voltage to the coil and use the timer to record the time difference between coil energization and contact closure or opening. Repeat each measurement at least five times.
A critical step is accurate contact state detection. Use an optocoupler isolation circuit to eliminate mechanical vibration interference. When the contact closes, the optocoupler’s output triggers the timer to start; when it opens, the signal drop stops timing. For solid-state relays, account for semiconductor turn-on voltage drop by adding a 0.5Ω sampling resistor in series to detect actual conduction timing.
Evaluate measurement error using both absolute and relative error. For example, if the set time is 10s and measurements are 10.12s, 10.09s, and 10.15s, the maximum absolute error is 0.15s and relative error is 1.5%. According to IEC 61812, industrial relays should have time error ≤±2%, and military-grade ≤±0.5%. If out-of-tolerance, check coil voltage stability, mechanical wear, or component aging.
Apply correction factors in special environments: compensate +0.3% per 10°C rise in temperature, and use double-shielded enclosures in strong electromagnetic fields. For digital relays with multi-range timing, verify switching accuracy across all ranges, especially carry-over errors during second-to-minute transitions. Reports must include environmental logs, raw waveform data, and correction calculations.
Calibration intervals depend on usage frequency: every three months for continuous-duty equipment, annually for intermittent use. Maintain historical data to create trend analysis and predict performance degradation. When systematic deviations occur, adjust variable resistors in the circuit or modify microcontroller timing code, then retest three times to verify correction. Final measurement data must be co-signed by a quality engineer and technician, and archived for five years.
