Cj Calibration; Cancel Calibration; Restore Cj Factory Calibration - Honeywell 900 User Manual

CJ Calibration

Each analog input card has two Cold Junction (CJ) sensors that are used in making thermocouple
measurements. These sensors may be re-calibrated in the field if desired to optimize thermocouple
measurement accuracy using the following procedure.
ATTENTION
An inaccurate CJ calibration will affect the accuracy of your thermocouple measurements. If
you are going to perform CJ calibration, you must use a very accurate temperature-measuring
device. It is also important that you allow the temperature around the controller's terminal
block to stabilize for 10 minutes or more before you take the CJ temperature reading.
Perform the steps in the order shown in the following table.
Item
Instrument Status And
Instructions
Reference
Rack Number
Module Number
Channel Number
Select CJ Input
User Measured CJ
Temperature (Deg C)
Calibrate CJ
Save Cal
After calibration, return the Controller to Run mode. Use IO Calibration display (page 159) or Controller
Mode button (page 10).

Cancel Calibration

You can stop the calibration process at any time by pressing the Cancel Calibration button. The status goes
to "ready" and the previous calibration is restored.

Restore CJ factory calibration

This restores the selected cold junction sensor to its factory calibration settings. Enter the rack, module and
channel, then press Restore Factory Calibration. Status will show "Restore CJ Input", then green "Done" or
red "Restore CJ Failed." After calibration, return the Controller to Run mode. Use IO Calibration display
(page 159) or Controller Mode button (page 10).
Revision 9
May 2014
This displays the status at each step of calibration. In order of appearance:
Ready
Measure CJ Temperature & Enter
CJ Cal Input
CJ Cal Failed (red) or Done (green)
Save CJ Calibration
Indicates CJ temperature reading in Degrees C. Also indicates an invalid module or
channel.
Enter the rack number, module number, and channel number of the CJ sensor to be
calibrated. Channel 1 is the top CJ sensor, Channel 2 is the bottom sensor.
Select this to verify that the displayed module and channel are correct.
Place your temperature-measuring device at the terminal that is closest to the selected
CJ sensor. Allow the environment around the terminal block to stabilize for at least 10
minutes before taking the temperature reading. Enter the measured temperature here,
in Degrees C.
Select this to start calibration. Calibration takes 30 seconds. Status will indicate when
calibration is complete.
Select this to save the calibration.
900 Control Station User Guide
Description
I/O Calibration
CJ Calibration
163