5.11 Model 330-4X (Thermocouple) Calibration; 5.12 Model 330-4X (Thermocouple) Internal Offset Adjustment - Lakeshore 330 User Manual

Lake Shore Model 330 Autotuning Temperature Controller User's Manual

5.11 MODEL 330-4X (THERMOCOUPLE) CALIBRATION

1. Follow the REMOVE TOP procedure in Paragraph 5.6.
2. A/D Calibration: Connect V+ lead of voltmeter to TP2 of the main board, and the V– lead to TP1. Adjust
this voltage with R10 until it reaches 2.5000 volts.
3. Zero Calibration: Disable room temperature calibration over the front panel. Short the two TC input
terminals with a very short piece of wire. Change the display to mV units and adjust R6 for Channel A or
R8 for Channel B. Adjust until the display shows 0.0000 mV.
4. Compensation Calibration: Enable room temperature calibration over the front panel. Select Celsius for
display units. Keep the two TC input terminals shorted. Adjust R28 (TP COMP) until display shows current
room temperature (20 to 30 °C range).
5. Verify linearity with a voltage standard connected to TC input terminals. Check at both +10 mV and –10 mV.
6. Follow the REPLACE TOP procedure in Paragraph 5.6.
Once the actual thermocouple is attached to the input, it may be necessary to adjust R28 to correct for any
unusual junction effects at the input terminals.

5.12 MODEL 330-4X (THERMOCOUPLE) INTERNAL OFFSET ADJUSTMENT

When attaching a new or different thermocouple to the controller, adjust the offset to compensate for
discrepancies in thermocouple material, leads and connections. The Model 330 provides offset adjustment
trimpots to allow offset calibration of the thermocouple.
NOTE: The offset adjustment compensates for the thermocouple used in the calibration. If another
thermocouple is attached, or the thermocouple has aged, or the configuration of the system is changed, then
repeat the offset adjustment.
1. Follow the REMOVE TOP procedure in Paragraph 5.6.
2. Place the thermocouple in a reference bath of known temperature (liquid nitrogen, ice, etc.). Allow the
system to stabilize to the reference temperature.
3. On the Model 330 front panel, select the thermocouple input and the desired temperature units.
4. Turn on thermocouple compensation.
5. Adjust the offset adjustment trimpot (R6 for Channel A and R8 for Channel B) so the displays read the
reference temperature.
6. Follow the REPLACE TOP procedure in Paragraph 5.6.
Service & Calibration 5-9