Temperature Calibration

TEMPERATURE CALIBRATION

Gaston County controllers require input from a number of temperature sensing devices. The devices used are typically 100 ohm, platinum-type RTD's (resistance temperature devices). The sensors found on most machines are:

	RUN RTD - This senses the current running temperature of the machine. It is typically installed in the system piping near the heat exchanger outlet.
	FILL RTD - This senses the temperature of the fill water entering the machine. It is located in the fill water line between the blend valve and the main fill valve.
	BACKUP RTD - This is a safety device and is usually located in the lower part of the vessel or system piping.

CAUTIONS

These calibration procedures should only be performed by qualified electrical technicians who are familiar with Gaston County equipment and controllers. Adjusting temperature circuits on operating equipment can be hazardous. Never adjust backup safety temperature switches beyond safe operating temperatures of the machine as shown on the ASME nameplate of the vessel.

APPLIES TO

MP6000 and MM3000 controllers.

PREREQUISITES

Supply valves to the machine should be shut, locked-out, and tagged per OSHA regulations. Main pump starter disconnect should be turned off.

EQUIPMENT REQUIRED

	RTD Simulator
	Multimeter
	Optional - Shake-down thermometer or other verification device

PROCEDURE

1. RUN RTD Calibration

1.1. Remove power from controller. Disconnect wire from "-" terminal on RUN RTD transmitter. Attach "+" lead from multimeter. Attach "-" lead from multimeter to wire removed from "-" terminal on transmitter. Set multimeter to measure DC current in milliamps. This will show the output from the transmitter to the controller.

1.2. Disconnect wires from the RUN RTD. Attach an RTD calibrator to the wires from the controller. Leave the wires from the RUN RTD unattached. Re-apply power to the controller.

1.3. Set the calibrator to 0 degrees Fahrenheit. Observe the milliamp reading on multimeter. Adjust ZERO trimpot on RTD transmitter to achieve 4 milliamp output as observed on multimeter. Indicated temperature on controller screen should be 0 degrees.

1.4. Set RTD calibrator for 300 degrees. View indicated temperature on controller screen (or supervisor screen on MM3000 controllers) Adjust SPAN trimpot on RTD transmitter to achieve a 300 degree indicated temperature. Observe the milliamp reading on multimeter. The expected output from the transmitter is 20 milliamps (+/- .2 ma).

1.5. Repeat steps 1.3 - 1.4 until no further adjustments are necessary.

1.6. Remove power from the controller. Remove multimeter. Reattach wire to "-" terminal on transmitter. Remove RTD calibrator and reattach RTD.

NOTES: RTD's can be checked with a multimeter set to ohms