The piezo stages supported by the E-712 can be operated in servo or open-loop mode. When spec makes a connection to the controller, spec queries the current setting of each stage. If in open-loop mode, spec uses the SVA command to move the motor and the VOL? command to read the position. In servo mode, the commands MOV and POS? are used. The mode can be changed using the "servo_mode" option to motor_par(). The "servo_mode" parameter can be also added to the hardware config file as a nonstandard optional parameter, as described below.

When in open-loop mode, there is no status available from the controller as to whether the move has completed or if the stage is on target, so moves are considered complete virtually immediately after sending the move command. Configure the settle time and dead band parameters, described below, if delays are needed.

On the Motor screen of the configuration editor, choose the controller type as PI_E712. An appropriate value for the steps-per-degree parameter is 1e6. The slew rate, base rate and acceleration time are not used by spec for this controller. However, some of the standard optional motor parameters, reached by typing a lower case m from the main motor configuration screen, are recognized and may be useful.

To configure a settling time at the end of each move, set the optional parameters DC dead band ("dc_dead_band") and DC settle time ("dc_settle_time"). If those parameters are configured, after the controller reports the move is complete, spec will continue to wait an additional time given by the settle time before reporting the move complete. In addition, spec will also wait for the difference between the target position and the actual position to be within the dead band. If the motor doesn't settle within five seconds, spec reports an error. Note, the dead band and settling time parameters set here are not associated with the controller's internal on-target tolerance parameter (0x07000900) and settling time parameter (0x07000901).

Additionally, the read-back slop parameter ("slop") and/or the hardware read-mode parameter ("read_mode") can be used as needed to suppress position discrepancy messages. If the slop parameter is set to some number of steps, spec will not report position discrepancies smaller than that value and will instead silently accept the reported hardware value as the position. The read-mode parameter controls how often the position is read from the hardware and can also tell spec to always accept the reported hardware value, no matter how large. spec normally assumes a motor is at its last position. If the PREMOVE read-mode option is set, spec will always read the hardware before moving the motor. If the ALWAYS option is set, spec will read the hardware whenever the get_angles command is run from user level. If the NO QUERY option is set, spec will always assume the hardware is correct and not query the user as to how to resolve the discrepancy if the returned hardware position differs from the current software position. If the NO QUERY option is set, the "slop" parameter is not used.

PARAMETER CLASSES

The E-712 has hundreds of parameters which are described in more detail in the Physik Instrumente user manual for the controller. Physik Instrumente assigns the parameters to nine classes, each associated with a particular function, as follows:

 Servo - logical axis
 Input - input channel
 Output - output channel
 System - whole system
 DDL - Dynamic Digital Linearization
 StdIF - standard interfaces
 WaveGen - wave generator
 Recorder - data recorder
 FW_Update - firmware

For any given class, there are values for a varying number of channel or index identifiers. For example, there are as many Servo indices as there are logical axes. The number of Input, Output and FW_Update indices depends on the hardware model. Some System parameters have only one index while the number of indices for other System parameters depends on the hardware model. There is only one index for DDL, StdIF, WaveGen and Recorder parameters for all hardware models.

Each parameter is associated with a unique hexadecimal number code, an axis (or index) identifier number from 1 to the maximum number of indices, a class as listed above, an attribute that indicates what privileges are need to modify the parameter and a description of the parameter. spec only allows modification to unprotected parameters. For other parameters, the controller requires a password to make changes.

PARAMETER DISPLAY

Various parameter attributes can be displayed with options to the motor_par() function, as described below. For example the following displays non-zero parameters associated with axis 1 of the controller: