Data Translation DT9828, User Manual

Page: 85 / 116

Calibration
85
Calibrating the CJC
If you are using thermocouples, you must calibrate the CJC for each analog input channel
using an accurate temperature input. For this purpose, it is recommended that you use a
stirred calibration bath, such as the Hart Scientific 7320 or equivalent. The calibration bath that
you select should have an accuracy of at least ±0.01
°
C. In addition, you must have a known,
calibrated thermocouple (a type K thermocouple is recommended).
To calibrate the CJC, perform the following procedure:
1. Immerse one end of the thermocouple into the calibration bath.
2. Connect the other end of the thermocouple to the analog input channel that you want to
use.
3. From the CJC Offset Calibration section of the dialog box, enter the following values:
−
Temp Target – The exact temperature of the calibration bath.
−
Thermocouple Type – The type of thermocouple that is connected to the analog input
channel (Type B, Type E, Type J, Type K, Type N, Type R, Type S, or Type T).
−
Channel – The analog input channel (0 to 7) to which the thermocouple is connected.
−
Unit – The temperature unit of the CJC measurement (C, F, or K).
4. Click Run .
5. Ensure that you have connected your thermocouple to the appropriate channel, and set
up the parameters properly, and then click
OK .
The temperature reading is returned along with the calibrated CJC offset value.
6. Repeat steps 2 through 4 for each of the remaining analog input channels.
7. When finished, click Done to close the DT9828 Series Calibration Utility.
Note: If you are not satisfied with the CJC calibration, you can load the factory default
settings stored in the EEPROM by clicking Restore Factory Settings .