Tachometers measure rotational speed (RPM) of motors, spindles, shafts, and rotating machinery. Calibration verifies the accuracy of both contact and non-contact (optical/laser) measurement modes using a reference speed source. Accurate RPM measurement is critical for machine setup, vibration analysis, and process speed control.
Inspect the tachometer for physical damage, lens cleanliness (optical types), and proper display function. For contact types, check the condition of the rubber tip and adapter cones. Verify battery condition.
Using a calibrated reference speed source, verify the tachometer reading at a low RPM point (e.g., 100-500 RPM). Record the tachometer reading and the reference value.
Test at a mid-range speed (e.g., 1000-3000 RPM). For optical tachometers, ensure the reflective tape target is properly applied and the sensing distance is within specification.
Test at a high-speed point near the tachometer's maximum range (e.g., 10,000-30,000 RPM). Record the reading and reference value. High-speed measurements are more susceptible to triggering errors with optical types.
For contact tachometers, verify accuracy using each adapter tip (surface speed wheel, cone adapters). Different adapters affect the measurement through the conversion factor.
Record all readings, reference speed values, measurement mode, and errors at each test point. Issue the calibration certificate and apply the calibration label.
RPM reading error must not exceed ±0.05% of reading for optical/laser tachometers, or ±0.5% for contact types, or per manufacturer specification. The instrument must reliably trigger at all test speeds without double-counting or missing pulses.
12 months
Contact tachometers use a rubber tip pressed against the rotating shaft to measure RPM mechanically. Non-contact types use a laser or LED beam reflected off a reflective tape target to count rotations optically. Non-contact types are safer for high-speed measurements and do not load the shaft.
Common causes include multiple reflective targets (giving double the actual RPM), dirty or misaligned reflective tape, ambient light interference with optical types, worn rubber tips on contact types, and low battery causing unstable triggering. Proper setup eliminates most error sources.
Yes, a calibrated stroboscope can serve as a reference speed standard. Set the strobe to the known speed source RPM and verify the image appears stationary. Then compare the tachometer reading to the strobe setting. Both instruments must have known accuracy.
CalibrationOS tracks due dates, stores certificates, and generates audit-ready reports.
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