Encoder lines vs. encoder counts

Yu Zou

Expert 1190 points

Other Parts Discussed in Thread: LVSERVOMTR

Chris,

Another quick question,

To update USER_MOTOR ENCODER_LINES in User.h, I checked my motor encoder which shows 4000 counts/revolution.

Then, what is the number of lines then? I'm confusing the relationship bet. these two terms.

over 12 years ago

0 ChrisClearman over 12 years ago

TI__Guru** 119680 points

Let me verify, but I'm pretty sure USER_MOTOR_ENCODER_LINES = counts/revolution / USER_MOTOR_NUM_POLE_PAIRS

so you would set (1000).

This is the same as the Teknic LVSERVOMTR we use.

0 Adam D. Reynolds over 12 years ago in reply to ChrisClearman

Guru 12800 points

The way this is defined is that lines = counts / 4. Lines refers to the number of lines on the encoder disc and counts refers to the resultant quadrature count seen by the QEP module.

0 Yu Zou over 12 years ago in reply to Adam D. Reynolds

Expert 1190 points

So, you mean 4 is fixed constant, which has nothing to do with # of poles, right?

0 Adam D. Reynolds over 12 years ago in reply to Yu Zou

Guru 12800 points

Correct. The 4 is based on how many counts there are per a line. For quadrature encoders, it it always 4.

0 ChrisClearman over 12 years ago in reply to Yu Zou

TI__Guru** 119680 points

Yes, my guess with POLES was incorrect.

It is fixed to /4

0 Yu Zou over 12 years ago in reply to Adam D. Reynolds

Expert 1190 points

This makes me wonder another term then:

What is the relationship bet. PPR and cnts/rev ?

0 Adam D. Reynolds over 12 years ago in reply to Yu Zou

Guru 12800 points

Pulses are the same as lines. So PPR = (cnts/rev) / 4.

0 Yu Zou over 12 years ago in reply to Adam D. Reynolds

Expert 1190 points

Thanks a lot, Adam.

0 Tran Binh Duong over 10 years ago in reply to Adam D. Reynolds

Expert 2550 points

Thanks a lot, Adam too!

Because I am having the same question.

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Encoder lines vs. encoder counts