Encoder Wiring


Thread Starter


I need to connect an encoder signal to 2 different sets of PLC inputs (2 Separate PLCs). Can this be accomplished without losing the integrity of the signal.

Steve Bailey


Make sure both PLCs are grounded to the same point. Make sure the DC common for both PLCs are connected together and the DC common for the encoder's power supply is connected to the same point.

After that, it's just ohm's law for two loads in parallel. Assuming the impedance for both PLC inputs is the same, the current through the encoder will be twice as high as when it's connected to a single PLC. Make sure it's within spec.

Bob Peterson

The anser is a conditional yes. Look at the signal characteristics of your encoder and make sure it can drive both inputs. If it can, you should have no problems as long as you make sure you have a common "common".

If not, or you need isolation, there are products available for this purpose. A Dynapar PM28 would work. You will need two if you require quadrature inputs to your PLC. There are other brands available, but I have used this one a fair number of times and found it reliable.

Donald Pittendrigh

Hi All

I have seen this done several times as a temporary
setup when upgrading PLC's, we have never had any
problems but grounding to a common 0V is important.

D Pittendrigh
Usually. A long as the combined load impedance is not too low for the current sourcing ability of the encoder. Do the math using Ohm's law.

Bill Sturm