User's Guide to Calibration of Analog Electronic Controllers in HVAC Systems,

The calibration of analog electronic proportional controllers requires the knowledge of at least three characteristics of the controller the action, the setpoint, and the throttling range. The calibration procedure follows these steps Measure the controller inputs Calculate the predicted controller output Measure the actual controller output, and Adjust the controller as required. Using this procedure, controller performance is evaluated at the control point, or actual condition, rather than the setpoint, which is the idealized, desirable condition. This means that only those controllers which are actually out of calibraton need to be adjusted - controllers that are in calibration need not have any settings or adjustments changed. If a controller cannot be calibrated or will not remain calibrated for a responsible period of time, it is defective and should be repaired or replaced.