When the Picomotor is biased at 120 V is there any extraneous movement, when you are changing channels or directions, as the 120-V offset in the driver waveform is discharged?
With the Model 8732 multi-axis driver, there is no movement either when changing channels or when changing directions. However, with the Model 8801 economical multi-axis driver and the Model 8701 single-axis driver, there will be minimal movement because the bleed off is slow and the piezo is decoupled from the screw. At most, you will see two steps worth, or about 50 nm. If you’re concerned about this, a simple solution is to approach the position from the “dir=low” direction so that the bias is at 0 V. Or, you can send two additional “compensating” steps to the driver when changing directions.
