The number of times I modify or design a machine and guess at the rotational speed is ridiculous, then I saw the Fitnate Digital Tachometer and for ~£16 I thought it was worth a go.
This is the DT-2234A and is a non-contact optical tacho.
This comes in a neat zipped pouch. It works really easily, place a piece of reflective tape on the rotating part. Best if there is a good contrast between reflective tape and dull/dark background. Point the handheld meter at the reflective spot from around 50 to 500mm away and hold down the test button.
- Instant readings from 2.5 to 99,999 RPM. Accurate to +/- 0.05
- Memory function, minimum, and maximum reading; features auto-zero adjustment
- Includes 4 pack of 24-inches (that is actually 24 inches in total) reflective tape
- 3 AA batteries.
- Measures at a distance from 2-20 inches
- Dimension: approx. 131 (L) x 70 (W) x 29 (D) mm (5.16 x 2.76 x 1.14inch)
The numbers can jump around at first, but you will rapidly get used to selecting a good location for a reading.
I checked out the Hobbymat MD65 with the spindle setup on the belts to give 1000rpm and I got a stable reading of 1010rpm.
The Fitnate Digital Tachometer is cheap, easy to work and on first inspection appears to give accurate results.