Despatch Protocol Controller - Manual (Page 29)

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WARNING: Calibration
equipment without internal
ambient compensation provisions
requires subtracting the ambient
mV signal from the calibration
temperature mV signal to
calibrate Protocol properly.
Figure 6. Top View of J Type Thermocouple Inputs on Protocol
Calibration Mode
Protocol has been tested and calibrated at the factory. Under normal operating
conditions recalibration should not be necessary. However, if the instrument does not
comply with known standards recalibration may be necessary.
Calibration Instructions
We recommend using a certified analog
thermocouple simulator/calibration source with less
than ±1
E F noise. We have experienced signal
stability problems with some microprocessor based
thermocouple simulator/calibrators which induce an
error during the calibration procedure. This error
generally results in a non-linear shift in the
controller's indicated temperature.
1. Disconnect AC power to the oven.
2. Remove Protocol controller to expose thermocouple input terminals.
3. Disconnect control and Hi-Limit thermocouples from controller thermocouple input
terminals (Control T/C, and Hi-Limit T/C).
4. Mark thermocouple leads if not labeled.
5. Connect a 6 foot piece of type J thermocouple lead wire to each of the Control T/C
and Hi-Limit T/C terminals.
6. Twist together or jumper the lead wire end not connected to the Control T/C and
Hi-Limit T/C terminals. This creates a junction and prevents a control sensor error
[S-T/C ERR] and Hi-Limit sensor error [H-T/C ERR] caused by an open
thermocouple.