One stepper motor using encoder for closed loop. Can I connect another encoder without using a motor and dual loop control?

[dg_lbe]

One stepper motor using encoder for closed loop.  Can I connect another encoder without using a motor? 

Using LabVIEW along with a PCI-7332 and an UMI7774 interface to drive a stepper motor with encoder feedback.  System is setup in closed loop mode for control.  Need to add another encoder to the system without attaching a motor.  I'm validating encoders one to the other.  Can this be done?  What kind of latency should I expect?  I've attached a simple vi.  Need an answer prior to purchase.

Thanks

[Wee-Bey · Accepted solution]

You can just hook up the second encoder to the second slot without having a motor there. Then you can use Read Encoder Position.flx to read its position or do what you want with it. As for latency, how much are you trying to get under?

[dg_lbe]

So any changes in MAX????

I know pc can represent +\- 15ms. But i think with the card a RTO the readings of both encoders at same time should be less than 1ms. Please provide your thoughts.
Thanks

[Wee-Bey]

There might be some latency from the LabVIEW calls, but if the connections from the motor to each encoder are similar, than that data shouldn't be separated in time too by more than a ms.

As for configuring in MAX, all you'd have to do is configure the second encoder like normal as if it had "no motor." In MAX, you might not be able to see both encoder counts at the same time, but you could in LabVIEW.

[dg_lbe]

Thanks for your support. Was able to confirm and works with an encoder simulator. So if both encoder reads are in the same while loop they both should be in sync +\-1ms? Or less???

[Wee-Bey]

If in the same while loop, I'd stay on the safe side and say less than 1ms, but you shouldn't get much latency at all. 🙂