American Magnetics 286 Multi-Sensor Liquid Level Instrument (CE-Marked) - Manual (Page 56)

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Operation
Sensor contamination
The instrument is typically shipped from the factory with a zero
setting for the fill timeouts.
4.2 Sensor Contamination
To ensure proper instrument calibration and operation, care must be
taken to ensure the sensor is kept free of contaminants and not subjected
to any force which would physically distort the sensor. Water or other
electrically conducting substances in the sensor will disturb the measured
capacitance and the instrument’s response. Physically distorting the
sensor in any way will also cause abnormal instrument operation by
introducing variations in the sensor capacitance not due to liquid level.
The absolute calibration of the instrument can be inaccurate if care is not
taken to ensure the sensor is in the proper environment.
Cold sensors exposed to humidified air can show erroneous high level
readings because the air contains moisture that can condense between the
cold sensing tubes. A minute film of water can cause a shorted or partially
shorted condition, which results in false level readings. As the sensor
warms, the moisture may evaporate and the sensor will again read
correctly. This is a physical phenomenon and does not indicate any
problem with your AMI level equipment. Limit or eliminate exposure of
cold sensors to humidified air to avoid this condition.
If a sensor should require cleaning and the sensor is for use with liquids
other than liquid oxygen, flushing with pure alcohol is recommended. The
sensor cannot be used again until all the alcohol has been evaporated.
Under no circumstances should the sensor be disassembled.
For sensors to be used with liquid oxygen (LOX), although measures are
taken to minimize oils and greases during manufacture, no special
cleaning required for LOX service is provided by AMI. Certified LOX
cleaning is the responsibility of the customer.