How to remove noise pick up from missing pulses of encoder ?

Question

Due to noise pick up of VFD near by, few pulses are missing or added in a PID controller from Encoder /Proximity switch out put. How to get exact pulse reading with out missing/ added by keeping VFD (Variable Frequency Drive) near by place. Encoder/Proxy is not connected to VFD. It is connected to Programme controller installed near the VFD Panel.Condensor,resistance etc., already tried but failed. What do you suggest inorder not to miss the pulse?

Answer 1

Sounds like either your shielding on the cable is not connected right, should only be connected one side, or you are not using shielded cable (very important). Another possibility is a grounding loop on the VFD or encoder cable. This is basically a iron sleeve, grounded to earth ground with your cable looped through it a close to the device as possible to reduce interference.
Other things to check are your encoder resolution, calculations your plc does to read the encoder, maximum RPM of encoder. I assume it is an incremental encoder, but would an absolute encoder work better?

I hope some of this helps.

Answer 2

The solution really depends on exactly what is picking up the noise. The encoder itself? Cable? Controller? Or even the raised ground potential?

Simple solution may be to relocate the sensor or the VFD. Or - if it is in extremely noisy environment and ground potential issue can not be resolved, use an optical isolation.

Answer 3

The best i have found is a metal oxide varistor, three for 3ph 2 for singlephase. In an amp range sutable for you system . the r/c network in side will surely help . Also the MOV can be used on the line side at service entrance to reduce spurious harmaonic events. Which have freqency implication and motor speed responses..and recuce conduit inductive heating. Good luck on your VFD. If your using your Vfd to get 3ph from single ph and frequency offsets are plaguing you Gang up the MOV's .....Read about Rc/networks and how to size them...also rotary converters..Good luck From The E!

Answer 4

I'm sorry you're feeling that way; while I would never do that to you, there are some who do, sad to say. The only advice seems to be what some of the atheists told me when I complained of feeling picked on by atheists, which is to grow a thicker skin. The only thing is, when you're forced to keep growing ever-thicker skin, you reach the point that you're ugly and you can't feel anything! :) How 'bout a hug from a Christian? (((darkfires angel))) Add--Yes, some people just come on here to be mean. Yesterday someone answered my question with a threat to kill all Christians--they're just nutters.