Cold Junction adjustment | Omega Speaker Systems DPS3301 instruction

Cold Junction adjustment:

After setting Heat/Cool mode, the next parameter is the cold junction reference temperature adjustment. The display will first show 'COLd JN' , and then the cold junction temperature will be indicated. Use ‘^DIGv’ key to adjust until the display reads the proper temperature. Once the correct temperature is displayed, push ‘SETUP’ key to enter that setting and go to temperature Calibration mode.

NOTE 1: The unit comes pre-calibrated from the factory. However, the above procedure can be used if any adjustment is required to the Cold-junction reading.

NOTE 2: Cold-junction temperture is the temperature of the connector that connects the thermocouple to the unit. This temperature is usually higher than ambient temperature, particularly after the unit has been powered for some time. This is due to the heat generated by internal electronics of the unit. For precise calibration, measure the temperature at thermocouple connector and then adjust Cold-junction reading.

NOTE 3: No cold-junction calibration is required for RTD or thermistor units. Therefore, this step is omitted in RTD or Thermistor units.

Thermocouple Calibration:

For base-metal thermocouples (type J, K, T and E), calibrating one type of thermocouple calibrates all. While calibration can also be performed outside of setup procedure (in main Process display mode), doing this in ‘SETUP’ eliminates flashing ‘PROCESS’ message from interupting the procedure. Also, raw A/D input can be viewed in this mode by pushing ‘SETPT’ key. This allows for adjusting any offset errors and thus allows for more precise calibration.

Thermocouple Calibration Procedure

Note: Make sure the unit is reading correct cold-junction temperature before calibrating.

If incorrect, adjust as described in the " Cold Junction adjustment" section.

For thermocouple calibration (type J T/C), following steps should be performed. Note that only one type of thermocouple need to be calibrated (i.e. J,K,T or E). For example, if the calibration is done for a type K thermocouple, types J, T, and E are automatically calibrated.

1.Connect a thermocouple calibration source to the signal input connector.

2.Dial in 725 degrees centigrade (Note: unit must be programmed for displaying in centigrade).

3.Adjust gain pot on the back of the instrument (ref. Fig. 7, Pg. 21) until the display reads '725'.

4.Short the input connector with a wire or shorting bar (make sure the source is removed so as not to damage it --- shorting the input connector will short the output of the source).

5. Push ‘SETPT’ key. The display will read 'U 00002' --- or some other value.

6.Adjust offset pot on back of instrument (ref. Fig. 7, Pg. 21) until the display reads '0000'.

7.Push SETUP key once -- the display should read close to Cold Junction temperature.

8.Remove the shorting bar from the input and connect the thermocouple calibrator again.

9.Repeat steps 2 through 7 till the unit reads proper temperature.

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