Choosing a Tachometer - Optical, Contact or Stroboscope?
Tachometers measure revolutions per minute on motors, shafts, fans and machine tools. This guide compares optical, contact (mechanical) and stroboscopic instruments by measuring range, accuracy and contact method, and shows which principle suits your workshop.
View tachometersWhat measuring principles exist?
Tachometers work on three principles. The optical tachometer counts the reflections from a marker without touching the part, the contact (mechanical) tachometer is pressed against the rotating shaft with a tip or measuring wheel, and the stroboscope makes the rotating part appear to stand still using a flash frequency.
Optical and stroboscopic methods are non-contact and therefore reaction-free, adding no load to the machine. Mechanical meters need direct contact and an accessible shaft end, but they deliver stable readings even at very low speeds.
Overview of measuring instruments for workshop and maintenance.
Read the guideHow do range and accuracy differ?
The measuring range spans roughly 0.5 to over 99,999 RPM depending on the device. Optical meters typically reach about ± 0.05 % of reading plus one digit, mechanical meters sit at ± 0.5 to 1 %, and the stroboscope depends on the resolution of its flash frequency.
- Optical: apply a reflective strip, aim from 5‑50 cm away, ideal for quick spot checks.
- Mechanical: fit an adapter (cone for the shaft centre, wheel for surface speed) onto the shaft.
- Stroboscope: set the flash frequency until the part appears still - also for vibration and motion analysis.
- Many combination meters unite optical and mechanical in one handheld unit.
Which device fits which task?
The choice depends on access, speed and environment. If the shaft is freely accessible and slow, a mechanical or combination meter is enough. For high speeds or hot and hazardous parts, non-contact measurement is essential.
- No access to the shaft end or high speed: optical tachometer with a reflective mark.
- Very low speed or surface speed (m/min): mechanical with a measuring wheel.
- Vibration and motion analysis, rotating patterns: stroboscope.
- General workshop use: combination meter, optical plus mechanical.
Frequently asked questions
Optical or mechanical - which is more accurate?
Optical tachometers are usually more accurate at around ± 0.05 % and measure without contact or reaction. Mechanical meters (± 0.5‑1 %) win at very low speeds and where no reflective mark can be applied.
What is a stroboscope used for?
A stroboscope makes rotating or vibrating parts appear to stand still. This measures speed without contact and lets you visually inspect belts, gears or vibration while the machine runs.
How do I apply the reflective mark?
Stick a piece of self-adhesive reflective tape onto a clean, grease-free spot on the shaft. The sensor counts one reflection per revolution; with several marks, enter their number in the device.
What is RPM versus m/min?
RPM measures rotational speed (revolutions), m/min measures surface or line speed. For m/min you use a measuring wheel of known circumference, for example on belts and wires.
Looking for the right tachometer?
We stock optical, mechanical, combination and stroboscopic tachometers for motors, fans and machine tools - including accessories such as reflective marks and measuring wheels.
Calibration ready
Instruments with a traceable calibration certificate on request.
Wide measuring range
From a few up to over 99,999 RPM covered.
Non-contact or contact
Optical, mechanical and stroboscope in our range.
Expert advice
Our measurement specialists help you choose.