The Feedback tab of the jrk configuration utility controls the measurements of the output of the control system. If this section is properly configured, the value of scaled feedback will be 0 when the output is at the minimum position and 4095 when the output is at its maximum. There are three available feedback modes:
The scaling options in this tab determine how the raw feedback values map to scaled feedback values, which are intended to be a representation of the output of the system. The parameters Maximum and Minimum should be set to the maximum and minimum possible values of the output; these will be converted to scaled feedback values of 4095 and 0, respectively. If the feedback leaves the range specified by the Absolute Max and Absolute Min parameters, a Feedback disconnect error will occur. For convenience, the Invert feedback direction option is provided. Select this option if the direction of motion that you would like to call positive actually results in a decreasing feedback value.
Clicking the button labeled “Learn…” allows scaling values to be determined automatically: with the motor off, the program will request that the output be moved to its minimum and maximum, and the resulting values will be recorded.
Input analog to digital conversion
In analog mode, the analog to digital conversion panel lets you specify the number of analog samples to average together each PID cycle, which determines the precision and speed of the analog to digital conversions. The indicator labeled “PID period exceeded” at the top of the window is provided as a warning for when the analog sampling takes more time than the specified PID period.
Selecting the Detect disconnect with AUX option activates an extra feature that allows the jrk to detect if the FB pin becomes disconnected from the analog voltage input device or shorted to 5 V. This option is intended for use in analog voltage feedback mode with a potentiometer connected between AUX and ground. When the option is selected, the jrk will periodically drive the AUX pin low, verifying that this results in a 0 V signal at FB. If the line does not respond as expected the Feedback disconnect error will occur.