Sampling the same encoder data from two different hardwares

[profx1288]

Hi, 

My system composed of 6 7358 motion control cards, 4 7654 servo motor drives, 4 7774 UMIs, and 25 brushed and brushless DC motors. These motors have quadrate encoder and the encoder signals are connected to motor drivers and UMIs. The system works well. Now, I want to sample the about 100 encoder signals of these motor to another sampling device while the system works. I am planning to use compact RIO hardwares.

My question is that does connecting the same encoder signals to two different sinks causes any problem for the encoder signal shape (amplitude etc.) ?

Thanks 

[Buechsenschuetz]

It depends... I am afraid you have to dig somewhat deeper into the hardware specs of your encoder and your NI boards/devices.

In case the encoders have differential outputs you should use only one termination resistor and remove (or switch off) all other termination resistors. The termination resistor usually is placed at the farmost end of the data line. Using multiple termination resistors may cause too much current of the encoder output stage.

In case of TTL outputs, check the encoder data sheet how many TTL inputs can be driven by one encoder. Usually TTL devices have an output driving capability of 10 inputs or so.