Future Design MCT-MC 4.3, User Manual

Page: 115 / 186

MCT-MC
4.3
Offline Setup - 115 - FDC MCT-MC
10.5.1 Loop Calibration Offset
The calibration offset provides a two point offset; a low point offset and a high point offset. The two point offset
constructs a straight line (linear calibration) between the two points. To insure greatest accuracy, it is best to
calibrate with the two points at the minimum and maximum operating ranges for the system.
To begin calibration, send the low signal input to the loop control. If the process value does not match the
reference signal, adjust the low point offset so that the process value matches the reference input signal. Press
the button to switch to the high point offset and then apply the high signal input to the loop control. Adjust the
high point offset if necessary in order to make the process value match the reference signal.
Once the high point offset has been adjusted, press the button to switch to the low point offset and again apply
the low signal input to the loop control input. If the process value does not match the reference signal, adjust
the low point offset again so that the process value matches the reference input signal. Again press the button
to return to the high point offset and apply the high signal input to the loop control. Adjust the high point offset
if necessary in order to get the process value to match the high reference signal. This process may have to be
repeated several times depending upon the amount of offset applied. Each time the low or high offset is
adjusted, it can affect the opposite end of the calibration curve.
If the known calibration error of the loop input is the same at both the minimum and maximum operating range
of the system, i.e., a linear offset, you can simply enter the difference between the reference signal and process
value for both the low point offset value and high point offset value. If both the low and high point offsets match,
it shifts the calibration curve thus applying the value of the low/high point offset equally across the entire range.
For example, if the range of operation is -50.0 to 350.0 degrees and the error between the reference signal and
the process value is 0.7 at both the low and high range resulting in process values of -49.3 and 350.7, simply
enter the value of -0.7 for both the low and high point offset. This will shift the curve equally at both ends of the
curve so the resulting process values will be -50.0 and 350.0.