Installation manual

Series C Controller Configuration and Operation Manual
18-2  Athena Controls, Inc. 900M050U00
18.2 Determining the Simulated Input to be Used During Low
and High Calibration
18.2.1 Introduction
When calibrating the controller, you will remove the output wiring. You will remove the
input wiring and substitute an appropriate simulated input to the controller’s input
terminals.
• When calibrating for an RTD input, you will apply an appropriate resistance value
across the input terminals using a “decade box” or precision resistors as described in
18.2.2.
• When calibrating for an thermocouple input, you will use a thermocouple simulator to
provide input during calibration as described in 18.2.3.
• When calibrating for a linear input, you will use a milliamp, millivolt, or voltage input
device as described in 18.2.4.
18.2.2 Simulating RTD Input for Calibration
When calibrating the controller for use with an RTD input, you will remove the output
wiring. You will remove the input wiring and substitute an appropriate resistance across
the controller’s input terminals. For this purpose, good results can be achieved using a
“decade box” type of calibrator or using precision resistors. Use of an “active resistance”
calibrator (that simulates resistance with its circuitry instead of actually providing the
resistance) may not produce satisfactory results.
Before calibrating the controller, you must determine the correct resistance to apply. Two
resistance values are used, one for low calibration and one for high calibration. For RTD
inputs, each of these resistances corresponds to a calibration low and calibration high
temperature. The calibration temperatures depend on the specific type of input. The
values can be read from the CALoCALo (cal low) and CAHiCAHi (cal high) parameters in the CALCAL
(calibration) menu as described in Section 13.
For example, if the InPInP (input) menu tYPEtYPE (type) parameter is set to rtdrtd and the UnitUnit
(unit of measure) parameter in the dSPLdSPL menu is set to FF (Fahrenheit), then the
calibration low value displayed will be 32 and the calibration high value displayed will be
1414.
The table below shows the resistance that represents the RTD calibration low and
calibration high temperatures. Use this table to determine what resistance to apply
across the input terminals when performing the calibration procedure described in this
section.
Low Calibration High Calibration
Input
Resistance
Setting
in ohms
Temperature
Equivalent
in °°F (°°C) [°°K]
Resistance
Setting
in ohms
Temperature Equivalent
in °°F (°°C) [°°K]
RTD 100 ohms
32 °F (0 °C) [273 °K]
365.94 ohms
1414 °F (768 °C) [1041 °K]
RTD with
decimal
support
100 ohms
32 °F (0 °C) [273 °K]
221.95 ohms
622.4 °F (328 °C) [601.2 °K]