EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: Circlotron on December 11, 2018, 01:14:55 pm
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Got one of these today:
https://www.ebay.com.au/itm/UNI-T-1-set-Red-Gray-UT372-Digital-Display-Speed-Tester-18-4-5-6-3-4CM-N1U9-/283142056140?nordt=true&orig_cvip=true&rt=nc&_trksid=p2047675.m43663.l10137 (https://www.ebay.com.au/itm/UNI-T-1-set-Red-Gray-UT372-Digital-Display-Speed-Tester-18-4-5-6-3-4CM-N1U9-/283142056140?nordt=true&orig_cvip=true&rt=nc&_trksid=p2047675.m43663.l10137)
Didn't seem to work very well at all initially. Then I discovered that if you angled the beam 45 deg to the reflective surface it ran quite well. Question is - why wouldn't it work when the laser is pointing directly at (perpendicular to) the reflective surface? It showed a reading 20 or 30 times higher than actual rpm and very unsteady.
As far as accuracy is concerned it's pretty good. Connected a red LED to a function generator and aimed it at the receiver phototransistor. At 90,000 rpm equivalent (5-digit display) there was way less than 1 rpm error, judging by how long it spent on 90,000 vs 89,999.