Measuring RPMs – Monarch PT-99 Digital Non-Contact Optical Tachometer – MADE IN USA

One thing that we continually focus on are facts — and sadly manufacturer specs rarely seem to line up with real-world testing. So in order to provide you with the best information, we have invested in yet another piece of high-quality test equipment — the Monarch PT-99 Digital Tachometer.

The PT-99 is a very easy-to-use device that utilizes an optical LED beam (up to 36″ from an object). It reflects the LED off of a small piece of reflective tape & converts the data instantly onto the screen to show you what the “real-time” RPMs really are. In addition to this, it also has a memory setting which can report the min/max RPM readings also during testing.


Here are the specs on the PT-99:

  • Battery Powered (2 AA – Included)
  • 60 Hour Battery Life
  • Real Time, Min, & Max RPM Readings
  • Trigger Lock/Unlock Modes
  • Lightweight = 7oz
  • Dimensions = 7″ L x 2.5″ W x 2″ D
  • RPM Range = 5-99,999
  • Accuracy Range = +/- 0.01%
  • Max Distance = 36″ From Object
  • 1/4″-20 Tripod Mount

Since the PT-99 can easily take measurements from basically any spinning object — this means that we will be able to include testing with cordless power tools, corded power tools, pneumatic tools, power equipment, & gas engines!  As with most specs, we expect to see some big discrepancies between our results & those posted on the side of the box/tool.

For some quick tests in this initial video, we tested the following (with results) :

Milwaukee M12 Drill

  • Advertised RPMs = Mode 1 @ 400 rpm / Mode 2 @ 1,500 rpm
  • Actual RPMs = Mode 1 @ 383 rpm / Mode 2 @ 1,421 rpm

Husky Pneumatic Die Grinder

  • Advertised RPMs = 22,000
  • Actual RPMs = 21,062

RIDGID 15″ Floor Model Drill Press

  • Advertised RPMs = 450
  • Actual RPMs = 441

As you can see from results above, actual specs dont align with advertised ratings.  Keep in mind that there are factors which can/will cause false results — and the testing environment needs to be verified (each time we test a tool).  Having a fully charged battery is essential for cordless tools & having the correct “working PSI” is essential for pneumatic testing.

The Monarch PT-99 is very easy to use.  We decided to buy it (even though it is more expensive than entry-level units) because it is Made in the USA, has a 1-yr warranty, has a VERY low margin of error, & came highly recommended from multiple tool design engineers.  For the casual DIYer, this may be overkill…..but to get the most accurate results for you — it is the one we chose.

Check out the video to see it for yourself!