ATI
Model Q45CT Portable Transmitter
Part 5
– Calibration
32
O&M Manual
Rev-G (7/15)
temperature. Adjustments up to ± 5 °C from the factory calibrated temperature
are allowed. Press ENTER.
5. The calibration data gathering process will begin. The message
Wait
will flash
as data is accumulated and analyzed. The
°C
or
°F
symbol may flash
periodically if the reading is too unstable.
6. Once completed, the display will indicate
PASS
or
FAIL
. If the unit fails, the
temperature adjustment may be out of range, the sensor may not have achieved
complete temperature equilibrium, or there may be a problem with the
temperature element. In the event of calibration failure, it is recommended to
attempt the calibration again immediately.
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.
The toroidal sensor is 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.
