Analog Calibration - Overview
Analog Input Calibration
Analog input modules can accommodate five input types:
•RTD
•Thermocouple
•Ohms
•Volt and milliVolt
•
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 56 is an adaptation of the wiring diagram given in the installation section of this manual. This figure indicates how an 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 5 | HC900 Hybrid Controller Installation and User Guide | 141 |
9/03 |
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