Emerson TCL Troubleshooting When a Warning Message is Showing, Explanation Section

MODEL TCL		SECTION 11
		TROUBLESHOOTING
11.4 TROUBLESHOOTING WHEN A WARNING MESSAGE IS SHOWING
Warning message	Explanation	Section
Sensor Need Factory Cal	The sensor board was not calibrated at the factory.	11.4.1
Sensor Negative Reading	The chlorine reading is less than -0.5 ppm.	11.4.2
Sensor RTD Sense Open	RTD sensor line is broken or not connected	11.4.3
Sensor Temperature High	Temperature is greater than 155ºC (311ºF)	11.4.4
Sensor Temperature Low	Temperature is less than -20ºC (-4ºF)	11.4.5

11.4.1 Sensor Need Factory Cal

The sensor board was improperly calibrated at the factory. Call the factory for assistance.

11.4.2 Sensor Negative Reading

The analyzer converts the raw current from the sensor to ppm chlorine by subtracting the zero current from the raw current and multiplying the result by a conversion factor. If the zero current is larger than the raw current, the result will be negative.

1.Check the zero current. It should be less than about 50 nA. If it is greater than 50 nA, repeat the zero step.

2.If the zero current is in the correct range, the negative reading might be the result of the raw current or the

sensitivity being too low. A properly operating sensor should generate about 1000 nA for every 1 ppm of total chlorine. Recalibrate the sensor. If necessary, clean or replace the membrane and check the fill solution.

3.Replace the sensor.

11.4.3 Sensor RTD Sense Open

The analyzer measures temperature using a three-wire RTD. See Figure 11.3. The in and return leads are used to measure the resistance of the RTD. The third lead, called the sense line, is connected to the return lead at the sensor. The sense line allows the analyzer to correct for the resistance of the in and return leads and to compen- sate for changes in wire resistance caused by changes in ambient temperature.

1.Check wiring. See Figure 4.4 or 4.5.

2.Disconnect the sense and return wires and check the resistance between them. It should be less than 1Ω. See Figure 4.4 or 4.5.

3.Even though the sense line is open, the sensor is still usable. Use a wire jumper to connect the sense and return terminals on the sensor terminal strip. The temperature reading will no longer be corrected for the lead resistance, nor will the analyzer be able to compensate for changes in ambient temperature. The error could be several ºC or more.

4.Replace the sensor.

11.4.4Sensor Temperature High or Low The sensor RTD is most likely miswired.

1.Check wiring connections.

2.Disconnect the RTD in and return leads and check the resistance between them. See Figure 4.4 or 4.5. The resistance should be close to the values given in Section 11.5.

3.Replace sensor.

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