Electronics > Projects, Designs, and Technical Stuff
Rotary encoder accuracy - mine doesn't seem very good
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mikerj:
Looking at an Omron datasheet for a similar (but $$) encoder, it specifies a maximum phase variation between the quadrature outputs of +-1/8th of the period of one complete cycle.
Corporate666:

--- Quote from: IconicPCB on March 07, 2019, 07:36:12 am ---How will this cyclic error show up once the quadrature signals are decoded?

As for speed, use a tacho  these are used as positional sensors primarily.

If used to synthesise a tacho signal... apply a bit more averaging and you wont notice it.

--- End quote ---

As I mentioned in the first post, I am timing the pulses to determine speed.  This is necessary to accurately determine speed. 

Can't average it out when it's +15% on one side of the wheel and -15% on the other side of the wheel.  If the wheel was turning at sufficient RPM, that would work... but there are mechanical constraints I must work within on this project.

IconicPCB:
Sooo...whas the pulse rate you are seeing at the rotational speed in question... parts of an RPM?
few RPM?
tens of RPM
?













tecman:
Your machine rotating the encoder could have mechanical tolerances in the drive gearing that would give velocity variations within one turn.  If you can determine that the error is at the same rotary phase angle it could be the drive.   I have used many hundreds of encoders over my years (none chinese) and have never seen variations as you are seeing.  The disc which is typically photo lithographed could have reeors that you are seeing, but it would be a gross error in production, and would generally effect an entire batch of products.  I would be surprised by that.

paul
techman-001:

--- Quote from: tecman on March 08, 2019, 07:51:14 pm ---Your machine rotating the encoder could have mechanical tolerances in the drive gearing that would give velocity variations within one turn.  If you can determine that the error is at the same rotary phase angle it could be the drive.   I have used many hundreds of encoders over my years (none chinese) and have never seen variations as you are seeing.  The disc which is typically photo lithographed could have reeors that you are seeing, but it would be a gross error in production, and would generally effect an entire batch of products.  I would be surprised by that.

paul

--- End quote ---

Excellent point, my money is on this reason as the cause.  The OP needs to use a method of guaranteed rotational accuracy, perhaps on the cross slide of a lathe or milling machine etc.
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