You are here

Tachometer VS RPM

3 posts / 0 new
Last post
Davideo
Offline
Last seen: 2 years 3 months ago
Joined: 2017-09-19 15:38
Posts: 21
Tachometer VS RPM

For my project I'm doing some acceleration calculations wit a VESC connected over UART where I make use of distance and speed. To make sure my units make sense, I've been using the VESC-tool to look at the tacho and the rpm. when i manually turn my sensored motor around I get about 42 tachometer units per rotation. Surprisingly, when I use the VESC-tool to rotate the motor with 1000 rpm (rotations per minute right?) for just about exactly 1 minute my tachometer shows an increase of only 6000 units. In my logic this should be : 1000 rotations *  42 tachometer units = 42000 ( a neat factor of 7 off).

What exactly am I not quite understanding or doing wrong?

 

Thanks!

ThierryGTLTS
Offline
Last seen: 6 years 1 month ago
Joined: 2017-09-06 14:18
Posts: 116

Mechanical rpm or electrical rpm?!

Erpm = Mrpm x PP, PP= pole pair number of the motor.

If you have 14 magnets, it's right.

Have a Nice Day.

Thierry

Davideo
Offline
Last seen: 2 years 3 months ago
Joined: 2017-09-19 15:38
Posts: 21

Maybe it confused me because the interface of the VESC tool says RPM (though it has that strange 'w' icon there also). I am also using UART with an arduino (with rollinggecko's library) and asking for the RPM values out of the struct of data from the VESC. Seems like these both refer to the ERPM rather than the MRPM. Will act accordingly, thanks!