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MODEL TCL SECTION 11
TROUBLESHOOTING
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.
11.4.4 Sensor 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.
11.4 TROUBLESHOOTING WHEN A WARNING MESSAGE IS SHOWING