Honeywell HC900 User And Installation Manual page 207

Analog Input Calibration
Analog input modules can accommodate five input types:

RTD*

Thermocouple*

Ohms*

Volt

millivolt*

4-20 mA
*Not available on high level analog input modules.
Calibration values for each channel are stored in the module as numeric values paired with A/D conversion
counts corresponding to those numeric values. The numeric values are those identified as 'REFERENCE'
on the OI or HCD calibration displays; apply these values to the input terminals during the calibration
procedure.
For AI channels configured as thermocouple inputs, the stored calibration values are compensated by the
measured temperature of the terminals. Because of this observe the following rules:

If you plan on calibrating the 2 cold junction compensation devices, perform this operation first before
performing any thermocouple calibrations. However, because cold junction measurement inaccuracies
will be compensated in each individual thermocouple calibration, cold junction calibration may be
skipped.

After connecting the thermocouple extension wire to the terminals, you must wait for the terminal
temperature to stabilize.

If using a compensated calibrator, input the equivalent simulated temperature values corresponding to
the REFERENCE mV values. These will be the hi and low range values for the particular thermocouple
configured.
Figure 92 is an adaptation of the wiring diagram given in the installation section of this manual. This
figure indicates how a calibration device can be connected to the appropriate terminals of an analog input
module. The calibration device(s) must have the following precision characteristics:

TC, mVolts, Volts inputs: 1 microvolt resolution

Ohms, RTD inputs: .01 ohm resolution

4-20mA inputs: 4 microamp resolution
Revision 6
21 April 2017
HC900 Process & Safety Controller User and Installation Manual 193