My device is in constant alarm, I am certain there is no risk of carbon dioxide. What should I do?
It sounds as though the device may have suffered from sensor drift. This is not common but it is possible for devices kept in storage for extended periods of time.
I would, therefore, suggest you attempt an auto-zero calibration adjustment and then test the alarms of the device.
The auto-zero calibration adjustment can be done as follows:
Note. This involves the use of zero gas.
For instruments with no oxygen sensor fitted, zero gas must have no carbon dioxide (pure nitrogen is suitable)
For instruments with an oxygen sensor fitted, the zero gas must have 20.9% oxygen and 0% carbon dioxide. The balance gas will usually be nitrogen
- Whilst the A50 is switched on, press the 'Mode' button three times. The buzzer will bleep on each press. (Each press must be within 1 second of the previous press)
- If this is done successfully, the instrument will enter 'Technician Mode'. This is signified by the green indicator, which instead of flashing off for a brief period every few seconds will now flash on for a brief period every few seconds. If the instrument is left in this mode, it will return to 'normal operation' after a short period. If 'Technician Mode' is inadvertently selected, press the 'Mode' button once to return to 'normal operation' mode
- From 'Technician Mode', press the 'Mode' button four times. The buzzer will bleep on each press. (Each press must be within 1 second of the previous press)
- If this is done successfully, the instrument will show both the 'Alarm 1' and 'Alarm 2' indicators, indicating that 'Auto Zero' mode has been selected. If this is done inadvertently, or if another mode is selected, press the 'Mode' button once to return to 'Technician Mode' and then repeat this selection
- Pass zero gas over the sensor(s) for 2 minutes - for CO2 only units, a flow adaptor is fitted to the CO2 sensor, for CO2/O2 units a second flow adaptor is fitted to the O2 sensor
- To proceed with the 'Auto Zero' operation, press the 'Mode' button twice. (Each press must be within 1 second of the previous press)
- The instrument will then perform its 'Auto Zero' operation for a period of 1 to 2 minutes. It will bleep once on completing the test, after which the green indicator will stop flashing
- During the 'Auto Zero' period, the ‘Alarm 1' and 'Alarm 2' indicators show whether the sensor signal is within acceptable bounds. When the signal is acceptable, neither indicator will be on. If either indicator remains on, ensure that the sensor(s) is/are exposed to zero gas and the adapter(s) is/are seated correctly
- On completion of the test, you may accept the new setting by pressing the 'Mode' button twice, or alternatively, ignore the new setting by pressing the 'Mode' button once
- This will return to the 'Technician Mode'. The reading can only be accepted provided the 'Alarm 1' and 'Alarm 2' indicators are not illuminated
- To exit from 'Technician Mode', press the 'Mode' button once
- The A50 then restarts by performing the normal power-on sequence (4 flashes)
- If the 'Auto Zero' calibration adjustment procedure failed to work correctly, the procedure should be performed again, and if still faulty please contact the supplier or manufacturer for further support