Review on 🔎 HDE Optimal Digital Infrared Tachometer for Professionals by James Broome

I bought these (and a new 9 volt battery) to test the speed of a 110 volt 1/4 inch die grinder that I use recently bought. The grinder does not have a low speed specification and I wanted to know which attachment I can safely use at low speeds. In doing so, I encountered two problems. Initially, small reflective strips flew away at high speeds. This device can be accurate to over 20,000 RPM, but another way must be found to determine the point to be measured on the rotating device. Second, you REALLY need a dark background for the rest of the rotating area. After some searching I used a 2" Roloc pad holder. Eureka: low speed = 13.2k, high speed = 19.3k (slightly under the advertised spec of 20k). I also have a cordless drill from Milwaukee tested. Also those readings were slightly below spec. So someone is a bit optimistic about their specs. I don't know if it will be a rotary tool maker or a tool maker. However, the results are close enough for everyday use. Am it just me or the fine print gets even smaller.I had to scan the supplied manual onto my computer so I could read it.I've attached said scans to this review.Update: Tachometer off: about 10% lower.Two star rating .It's digital.You should be able to get closer.