Attention: If the reference air flow rate exceeds 60 l/h, it may cause a decrease in the temperature of the O ₂ sensor, triggering the "O ₂ probe temperature too low" error.

Sensor replacement and troubleshooting
4.1 Replacing the O ₂ sensor
Turn off the system power and remove the probe core.
Unscrew the filter head and remove the test gas distributor.
Loosen the 4 hexagon socket screws on the measuring unit flange and remove the old sensor.
Clean the flange surface and install a new sensor (pay attention to using new gaskets and screws).
Reinsert the inner core to ensure even spring pressure.
After installing the probe, perform 2-point calibration after running for 24 hours under process conditions.
4.2 Replace COe sensor
Warning: Before replacement, the COe measurement must be set to OFF through software, otherwise the new sensor may be immediately damaged.
Disconnect the COe sensor wiring (terminals 11-14).
Loosen the locking nut and remove the clamping ring, O-ring, and retaining ring in sequence.
Remove the old sensor (note possible high temperature).
Prepare a new sensor: Insert the clamping ring, O-ring, retaining ring, and locking nut, paying attention to the inclined surface facing the O-ring.
Insert the new sensor and tighten the locking nut. The system needs to be tightened again after running for 2 hours.
Reconnect the wiring, power on, enable COe measurement through software, and input the parameters on the sensor test certificate (RH ₀, Offset, Alpha, Beta, Gamma, Delta, SO ₂ correction values).
Be sure to confirm that the RH ₀ value is correct, as incorrect values can immediately damage the sensor.
4.3 Common faults and solutions
Possible causes and solutions for the fault phenomenon
The measurement value of O ₂ fluctuates greatly, and the wiring is loose, the internal contact of the probe is poor, and the filter element is damaged. Check the wiring and replace the filter head
If the O ₂ display exceeds the range or is too high, the probe or sensor flange may leak, or the flange may not be airtight welded. Check the seal and replace the O ₂ sensor or gasket
O ₂ shows 0% but the expected process is high. Heater failure, thermocouple failure, fuse blown, cable short circuit. Check the heater resistance (about 37.5-47.5 Ω), thermocouple resistance (2-80 Ω), and replace the fuse
No measurement value for COe, arrow displayed beyond physical range, COe sensor malfunction. Perform O ₂+COe sensor inspection and check electrical connections
Refer to low/high air flow rate, incorrect flow setting, insufficient air source, pump failure, and readjust the flow rate. Check the air source and pump
Electronic unit temperature alarm: If the ambient temperature exceeds the range of -20 ° C to+55 ° C, improve ventilation or ambient temperature
4.4 Error codes and relay outputs
The system error relay (terminal 19A/B) operates in the event of hardware failure, thermocouple disconnection, heating failure, calibration failure, etc., and the O ₂ signal output drops to 2.00mA (unless otherwise set). COe related errors output 20.80mA. Users can view specific error information through the system menu and attempt to reset. If the error persists, please contact ENOTEC service.
Long term discontinuation and storage recommendations
ENOTEC emphasizes that heating sensors must operate continuously. Frequent switching of heating power can cause thermal stress and shorten the lifespan of heaters, thermocouples, and sensors. If it must be stopped, ensure that the probe temperature drops below 200 ° C before opening the casing and wait for at least 1 hour. The storage environment shall be dry and ventilated to avoid paint smoke and silicon spray.
