Offset Calibration

Offset Calibration is the act of placing a sensor into a state where the output condition is known to be a certain value and then changing the measurement’s offset variable so that the sensor output reads as exactly that value. It is similar to a zeroing calibration, except that the known value is a non-zero value. By measuring the output of the sensor in this specialized condition (the known offset condition), the offset variable will be changed to ensure that this condition results in a measurement value that matches it. Note that this process only changes the offset variable that is shared between the measurement instruction and the FieldCal() instruction. The multiplier variable is unaffected.

A simple example of offset calibration would be placing an object of known weight (such as 10 lbs.) on a scale designed to measure the mass of objects. With a known weight on the scale, this is the condition in which the scale should give a known reading for its output. First the calibration is triggered, then the user informs the datalogger about the value of the known weight, and finally the offset is adjusted to ensure that the scale gives a properly matched reading for that condition.

To perform an offset calibration, use an argument of 1 (the number one) for the calibration type in the FieldCal() instruction of your CRBasic program. The Calibration Wizard can be used to calculate and apply the proper offset while the program is running in the datalogger, or code can be configured within the CRBasic program to trigger the offset event based on flags or other user-defined conditions that occur while the program runs.