It took me a while to figure out how to use this device. I was especially confused with the requirement that I enter in the "number of magnet pairs". This is because my test motor has six magnets but 9 poles. But, after experimenting with my laser tachometer, I was able to figure out that the magnet count is what matters and the value that I need to enter is the total number of magnets divided by 2, hence the term "pairs".
So, after "playing around" with this device using my test setup and my tachometer, I've discovered that this device is extremely accurate. As an example, this device gave 30,848 max rpm and my laser tach gave 30,867. That's a deviation of around 0.06 percent. Note that I didn't write "6.0" percent, I wrote "0.06" percent. I found the same kind of accuracy for KVM as well. This device has now become a very valuable addition to my hobby toolbox!Apologies to AEO for earlier review - seems it pays to READ THE INSTRUCTIONS!!
I had not set the requisite number of magnet pairs for the motors so the default setting of 6 pairs (12 magnets) accounts for the error in RPM and researching on the rc forums revealed that correct Kv is determined only at 100pcnt throttle.
Having set the correct magnet pair counts for each motor - the RPM is spot on with the laser and whether I use a 3S, 4S or 6S I get the same Kv value at 100pcnt throttle and guess what - they correlate with the motor specs..
Again, my apologies but i limit to 4 stars for the short cable and wandering pot..
Enjoy, it does the job and remember the hold feature which is handy for keeping post-experiment notes.
Oh, and another tip from the forums you can also use the potentiometer to check servo operation by plugging a servo into the esc port :)