ATI
Q45C2 2E Conductivity System
Part 5 – Calibration
O & M Manual
Revision K (01/07)
- 49 -
5.6
TC Factor Calibration
This function is intended to give the user direct control of the temperature
calibration offset value without having to proceed through the temperature
calibration procedure. Sensor TC offset is a number that indicates the sensor
RTD output at 0 ºC. Ideally, the sensor temperature output will be 0 ºC (1000
Ohms) under these conditions. Sensor offset is primarily the result of sensor
RTD tolerance and connecting cable resistance. Large offsets are typically the
result of large sensor cable lengths. A sensor reading of +1 ºC indicates that the
sensor will output an uncalibrated reading of +1 ºC when placed in a theoretically
perfect 0 ºC temperature bath. In other words, the offset shifts the entire sensor
response curve up or down. Since the slope of an RTD is fixed and highly
repeatable, the slope is not adjusted in this calibration.
Certain Q25 series sensors are labeled with a specific TC factor. Entering this
factor directly allows the user to quickly calibrate the transmitter for the sensor
being used without performing a time consuming full temperature calibration.
However, if the sensor cable length is modified or a new sensor is used, a new
TC factor must be entered or the user must perform a full temperature
calibration. The default value for the TC factor is 7.50. Increasing this value
increases the temperature reading and decreasing the value decreases the
temperature reading. A change of approxi0.1 is equivalent to +0.1 ºC.
This function is directly related to the full temperature calibration function in that a
new offset number is produced if a full temperature calibration has already been
performed. If the TC factor is modified, it overrides any previous full temperature
calibration data.
Procedure
Press ENTER to initiate user entry mode and the first digit will flash. Use arrow
keys to modify value; range is 00.00 to 15.00. Press ENTER to save the new
value.
