BPC303 Closedloop switching in Python

[TM0809]

Hi,
I have been trying to control the BPC303 piezo controller via a python script in closed loop and am having some challenges. Here are the issues:

1. Manual recommends setting the position sensor value to Zero by pressing the 'Zero' button in the GUI. Is the method for this operation channel.SetZero()? I noticed that the LED flashes on the display indicating that the sensor is zeroing when I run this script. Is there a command/method that can help me with figuring out whether the zeroing process is complete or not? This way I can write a wait function till this is complete
2. I notice that on the display after zeroing, the position mode LED switches to 'close loop'. However, when I output the mode from the script (channel.GetPositionControlMode()), it indicates open loop. Is there a reason for this?
3. Following the zeroing, when I try to change the position control mode to close loop and output the mode after a few seconds, it still shows open loop. Can you please let me know the reason for this?

At this point, I am unable to determine from the code whether the stage is in closed loop or open loop, which is not ideal. Can you please help me with these issues? I am attaching an image of my notebook output. Than you

[TrumanMetz]

Hello,
Thank you for reaching out. SetZero is the correct method for zeroing the position yes, and the boolean equivalent to determine if this is complete or not would be IsZeroed() or IsZeroing(). The latter returns true if the move is still taking place the former if the move is complete. There is a small message on the bottom of page 12 of the BPC manual that states the controller will go into closed loop mode, at least when zeroed through the GUI, but the GUI LED's aren't always 100% reliable so the LED on the controller might be a better indication if the mode has changed or not. There should be a small wait after setting the control mode so the system has enough time to update the status before the query, so as your script is written now it might be printing out the control mode before it actually gets a chance to change the status.

I hope this helps but if you continue to have issues, I highly recommend reaching to us at techsupport@thorlabs.com so we could better help with troubleshooting.

Best regards,
Truman Metz

[TM0809]

Hi @TrumanMetz , thanks for the response. I realized the problem maybe the SDK version and reinstalled Kinesis software and associated dlls. It seems like the issue is only partially fixed. The booleans channel.IsZeroed() and channel.IsZeroing() are not available options with the latest SDK. Are these methods related to the channel object or a different object? Thank you.

[TrumanMetz]

Hi TM,
Those properties are inherited from the PiezoStatus object but there doesn't seem to be a way to assign the call to a specific channel. This means for the most part IsZeroed is going to return true and IsZeroing is going to return false. So, my apologies for the confusion but with this being the case you'll want to just use getOutputVoltage() if you are in closed loop and getPosition() if you are in closed loop. For either of these they should return 0 if the piezo is homed.

I hope this helps,

Bets,
Truman Metz