I am trying to communicate with a device via RS-485. point-to-point, only 2 nodes.
The bus media is 200m of shielded twisted pair 22AWG inside a multiconductor cable.
in the other conductors of the cable flows 8-20kHz high voltage PWM from a VFD.
There is an exceptional amount of noise in the cable.
I am not using any termination resistors currently.
I can communicate just fine with my remote device when the VFD is not running.
As soon as I start the VFD, communication is destroyed.
All that I have read about RS-485 termination resistors talks about transmission line impedance and the resistors are to correct propagation delay.
My question is, in addition to affecting propagation delay, do the resistors do anything to help with the EMI? Would I see any benefit of implementing them, considering my setup works just fine without them, in the absence of EMI?
The bus media is 200m of shielded twisted pair 22AWG inside a multiconductor cable.
in the other conductors of the cable flows 8-20kHz high voltage PWM from a VFD.
There is an exceptional amount of noise in the cable.
I am not using any termination resistors currently.
I can communicate just fine with my remote device when the VFD is not running.
As soon as I start the VFD, communication is destroyed.
All that I have read about RS-485 termination resistors talks about transmission line impedance and the resistors are to correct propagation delay.
My question is, in addition to affecting propagation delay, do the resistors do anything to help with the EMI? Would I see any benefit of implementing them, considering my setup works just fine without them, in the absence of EMI?