The RTD transmitter is usually factory calibrated to the temperature range shown on the device name plate. When the performance deteriorate and the transmitter needs recalibration, the transmitter is normally calibrated by using a resistance decade box.
Materials Required for Calibration
To calibrate the RTD transmitter, the following equipment will be required:
1. Voltmeters (digital) of suitable accuracy and very high resolution – 1mv
2. A 24VDC power source
3. A 5 dial Resistance Decade Box with high precision providing 100Ω steps
|How to Calibrate RTD Transmitter|
- Locate the RTD transmitter terminal by removing the housing cover
- If an RTD is already connected, remove all the RTD lead connections
- Determine the RTD resistance at the desired base(0°C) and full scale temperatures
- Turn the power supply on
- Set resistance decade box to the resistance that corresponds to the desired base temperature. Adjust the zero pot (potentiometer) of transmitter until the output is 4mA
- Set resistance decade box to the resistance that corresponds to the desired full scale temperature. Adjust the span pot (potentiometer) of transmitter until the output is 20mA
- Repeat the above steps until both 4 and 20mA readings are obtained without readjusting span and zero potentiometers.