Infrared Non-Contact Measurement Digital Display photoelectric Tachometer, Digital Tachometer, Motor Tachometer, Automobile Motor Tachometer Measuring Range 2.5PRM-99999RPM

First, I like this unit, it's compact, light, and gets the job done. This photoelectric tachometer works well.It is good for my RC hobby and for use in engine work as well as electronics (checking fan speeds)I know it says it is infrared but it is not, it is a visible red laser tachometer, which frankly I prefer because you can see where the beam is pointing which is important in getting a good reading.it has all the basic functions you would want, on/off, auto or manual speed range, and a hold function. The backlight works well. the accuracy was dead on. it also comes with a cover for the optics (the laser and receiver end) and a soft case to store it in.I like that it also has an analog-type reading as well as digital, which makes it easier to recognize varying speeds. it also has an ambient temperature sensorthe instructions are very clear and easy to understand.it does not have built-in functions to compensate for multiple blades that might trigger it, so for example if your read off a 3-blade propeller the rpm will report 3x faster than it is. this is not a problem, it is just something to be aware of if you never used one before. Some fancy-schmancy ones have a setting to do the math for you ... this one does not and I prefer that anyway.it does come with a strip of reflective tape that is good for putting a reflective mark on something solid. to get a measurement.there is no physical on-off switch, just a soft switch, which means there is always going to be a small parasitic power drain. so for long-term storage, I will remove the batteries.oh, speaking of batteries it takes 3 aaa cells. i tested it with rechargeables and they worked well also. the batteries that come with it seem to be inexpensive carbon zinc, i swapped those out for alkalines.so summary, it is an effective tool that works as you would expect.