Overview:
Figure 1. 10Ω Cu RTD connection ("R" is the resistance leads from the RTD) |
Parameter sets of the Green Series controllers are loaded with factory input types including Thermocouples and 100Ω RTDs. Many industrial applications utilize a 10Ω Cu RTD as the temperature sensor of choice. This application note describes the setup and calibration for Green Series controllers for a 10Ω Cu RTD input.
A UM330 controller was used to demonstrate the procedure. The RTD measurement current, IRTD=0.13mA is standard for most Green Series controllers, so the calibration procedure example can be implemented on any green series controller. In this example, the desired PV meaurement range was 0-100°C.
A Temperature-vs.-Resistance table for a 10Ω Cu RTD was used to obtain the resistance values corresponding to the range high and low temperatures respectively. Two temperatures 300°F (= 148.9°C), -40°F (=-40°C), slightly above and below the PV range were selected from the T-vs.-R table. A voltmeter was then used to measure the corresponding voltages at the controller input terminals yielding Vlow = 1.04mV, and Vhi = 2.02mV. From this measurement, appropriate range values of RH=2.02, RL=1.04 were set. The scale high and low values SH, SL were set to the corresponding Celcius temperatures of SH=148.9, SL=-40.0. The controller was tested and found to be accurate for a 0-100°C measurement range with a 10Ω Cu RTD input. If a different PV measurement range is desired, e.g. 150-400°C, the parameters RH,RL,SH,SL must be set to values corresponding to these range endpoints.
Procedure for calibrating a Green Series controller for a measurement range of 0-100°C using a 10Ω Cu RTD
- Connect the 10Ω Cu RTD to the controller as shown in fig.1
- Set the parameter IN= 55 ( input type DC –10 to 20mV).
- Set the parameter SDP = 1.
- Set the parameters RH=2.02 and RL=1.04.
- Set the parameters SH=148.9 and SL=-40.0.
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