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MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)
18
4.4.2 Temperature / Flow Probe Connector
This indicator will light if the temperature probe is not correctly plugged in, or the
probe used is faulty. The humidifier tests for the following probe fault conditions:
• Temperature probe disconnected
• Chamber thermistor open or short circuit
• Airway thermistor open or short circuit
• Flow thermistor open or short circuit (shorted probe test)
• One thermistor shorted to another (shorted probe test)
• Flow calibration resistor open or short circuit (shorted probe test)
An alarm will be generated if any of the above faults are found, and the
humidifier will remove power from all heating systems.
NOTE: the shorted probe tests and flow thermistor tests are only performed on
start-up, or when temperature probe or heater wire alarms are cancelled.
4.4.3 Chamber Probe & Airway Probe
These indicators are used to show that either the chamber probe or airway
probe is not inserted into the breathing circuit correctly. On start-up, and during
rapid changes in temperature, the humidifier tests to see if a probe is in place by
cooling and then heating the probe. If the humidifier finds that either probe is
not inserted into the breathing circuit, an alarm will be generated and the
humidifier will enter stand-by. During this alarm the humidifier will initiate a
probe out test periodically, or a test will be initiated immediately after mute has
been pressed.
During periods of low or zero gas flow, the airway probe out alarm is disabled.
As soon as flow is detected however, an airway probe test is initiated.
NOTE: For software versions 7.22 and 7.23 in non-heater wire operation, the
airway probe out alarm does not function, instead the low temperature of the
disconnected probe will activate the temperature alarm (refer section 4.5).
4.4.4 Chamber or Airway Probe Alarm with Probe connector alarm
The humidifier checks to see if the temperature probe is faulty by testing for the
following conditions:
• Chamber temperature has been greater than 50 °C for 20 minutes
• Chamber temperature is greater than 80 °C
• Airway temperature has been greater than 50 °C for 5 minutes
• Airway temperature is greater than 80 °C
If an apparent fault is found, the humidifier will give a temperature / flow probe
connector alarm, and also indicate either the chamber or airway probe. The
humidifier will stay in stand-by until the chamber or airway temperature drops
below 50 °C. Once this occurs, a probe test will also be initiated.