(created 7/31/07)

If you suspect that the gauge is not properly calibrated, you may confirm your suspicion by measuring room temperature and the temperature of ice water.  To do this, however, all the thermocouples must be plugged into the yellow jacks.  If the gauge is, in fact, off, follow this procedure:

1.  Remove the four green adapters from the back of the gauge. 

2.  Remove the red and yellow wires from the green adapters. 

Now a small voltage must be applied across each positive-negative connection.  There are two blue and black splitters that were made just for this task.

3.  Attach the twelve wires from one splitter to all of the positive ports.

4.  Attach the twelve wires from the other slittler to the negative ports.

5.  Locate CNT's function generator (made by HP) and an op-amp with an output impedance of less than 10 ohms.

6.  Connect the + and - outputs of the function generator to the corresponding inputs of the op-amp.

7.  Connect the output of the op-amp to the negative inputs (making it a buffer).

8.  Connect the ouput of the op-ampt to the positive ports on the thermocouple gauge.

9.  Connect the negative ports on the gauge to ground.

10. Connect a millivolt meter (the multimeter works fine) between the positive and negative ports on the thermocouple gauge.

11.  Switch on the funtion generator and select an AC value of 0.

12.  Tune the DC value until the millivoltmeter reads somewhere between 28-32mV.

13.  Turn on the thermocouple gauge and select mode 9 (see the owner's manual).

14.  Using the two arrows on the front of the gauge, type in exactly what the millivoltmeter reads.

15.  Push the circle button on the gauge.

16.  Now it is calibrated.

A schematic of this circuit has been uploaded under the file name thermocalip.bmp

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