HomeInstallationInstall filter to lower encoder noise

Install filter to lower encoder noise

The fundamental is that the compliment channels that any modern encoder product has available are there for a reason, using them will effectively double your signal to noise radio. Additionally, a shielded cable is highly recommended anytime you are running low voltage signals next to a power wire, especially a wire carrying a PWM signal. Though different grounding configurations may help or hinder the resulting signal quality depending on the frequency and amplitude of ambient noise, a good rule of thumb is to try to keep the shielded cable at least 2 inches away from the power wire, in separate conduits, and when the two must cross do so with a 90 degree angle between them.

I've rarely seen noise on 24vdc encoders, typically single ended 5vdc encoders, though if the encoder cable isn't shielded then it's an antenna picking up the noise. One item that hasn't been mentioned is the motor brake. Check to see if it has a flyback diode across it. If it doesn't, you have a high powered inductor who's generating noise. Is the cable going straight back or through an interconnect? If it's going through a bulkhead, is the shield being passed through, 360 degrees? Is it making contact to the control panel (potential ground loops)? Or is it going through one of the pins (high impedance path will cause the noise on the shield not go back to the drive but somewhere else, such as the encoder wires)?

From aspects of installation you need to choose a well shielded cable segregating from HV cables additionally if it's an incremental encoder the configuration of bipolar is a good noise-immunized, which means you need 4 wires A/A-,B/B- at least from the encoder. If it's extreme circumstance you can choose a fibre as media.

Of course installing a reactor /dv/dt filter to the output of a VFD will reduce common noise and a shielded power cable is highly recommended to use.

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