Lo Gain; Check Linearity; Cold Junction Calibration - Altek 222A Quick Start Manual

LO GAIN:

Adjust the millivolt source to +77.600mV. The 222A should read 77.600mV ±0.009mV.
NOTE: The least significant digit may be bouncy.
If the 222A does not read 77.600mV ±0.009mV, adjust the Lo Gain pot #3, figure 1, so that the
222A reads within ±0.009mV of 77.600mV.
Flip dsw4 down for 2 or more seconds, then return dsw4 to the up position.
Readjust the Lo Gain pot #3 if the 222A does not display 77.600mV ±0.009mV.
NOTE: dsw4 must be placed down for 2 or more seconds every time the Lo Gain pot #3 is adjusted.

CHECK LINEARITY:

Adjust the millivolt source to the following voltages and check to make sure the 222A is in tolerance
at each voltage point.
VOLTAGE
-77.600mV
-60.000mV
-40.000mV
-10.000mV
Slide the Model 222A power switch to off and disconnect the mV source.

Cold Junction Calibration

Connect the leads of the Model 222A to the N.I.S.T. traceable thermocouple probe.
Place the thermocouple into the ice bath as described in note 1 (or ice point reference cell).
Place all dip switches down (dsw1-dsw4) and slide the Model 222A power switch to READ.
Wait approximately 10 minutes for temperature differences to settle.
Adjust the cold junction calibration pot #1 so the Model 222A displays a temperature of 32.0°F (or a
value that compensates correctly for any known inaccuracies of the thermocouple probe). Please
wait 10 seconds between adjustments to allow the 322 time to recalculate the cold junction
compensation.
Slide the Model 222A power switch to off.
TOLERANCE
±0.018mV
±0.015mV
±0.012mV
±0.007mV
VOLTAGE TOLERANCE
0.000mV
10.000mV
40.000mV
60.000mV
±0.006mV
±0.007mV
±0.012mV
±0.015mV