American Magnetics 286 Multi-Sensor Liquid Level Instrument (CE-Marked) - Manual (Page 104)

90
Service
Troubleshooting Hints
sensor will again approach the correct reading of 0%. This condition
can also be corrected immediately if liquid nitrogen is added to the
cold trap freezing the residual moisture. This is a physical
phenomenon and does not indicate any problem with your AMI
level equipment.
6. Verify the sensor is free of contaminants and is not subject to any
physical distortion. Disconnect the BNC connector at the top of the
sensor and measure the sensor resistance by placing an ohmmeter
across the center pin and the outer barrel of the connector. The
resistance of the sensor should typically be >10 M
Ω
.
6.2.3 One of the Model 286 channels reads instead of
displaying the level
1. Confirm that the input for the channel displaying is
properly connected to a sensor and oscillator, and that the correct
end of the oscillator is connected to the sensor (see markings on
oscillator).
2. Check the cable between the oscillator and the instrument to be
sure that it has no breaks or cuts.
3. There is a possibility of moisture in the connector at the top of the
sensor associated with the channel displaying .
Disconnect the BNC connection and remove any moisture. Moisture
or contaminants in any of the BNC coaxial connectors can short out
the sensor and cause a false
reading or other erroneous
readings. A pack of non-conductive electrical connection lubricant
(ECL or “Dielectric Tune-up Grease”) has been included with the
liquid level sensor packaging to reduce the possibility of this
occurring. Apply a small amount of ECL to any of the BNC
connectors that may be exposed to moisture. Mate the ECL-coated
connectors then remove any excess ECL from the outside of the
connector. Added protection can be achieved by covering the ECL-
coated connections with a short section of heat-shrink tubing.
Note
MSDS sheets for the ECL are available upon request.
6.2.4 One of the Model 286 channels reads instead of
displaying the level
The display indicates that the input which has been
assigned to the channel has not been calibrated. Check to make
sure that the intended input (A, B, C or D) is assigned to the
channel. If it is, then the input must be calibrated — see the
Calibration section beginning on page 17.