American Magnetics 187 Self-Compensating Liquid Level Controller - Manual (Page 65)

54
Service
Troubleshooting Hints
5.2.3 The Model 187 displays “Over/Under Flow”.
1. The vapor and liquid reference plate sensors are either both
submerged or exposed. The vapor reference plates should be
exposed at all times. The liquid reference plates should be
submerged at all times.
2. The dielectric between the vapor and liquid is not sufficiently
different to allow for operation of the Model 187. The dielectric
difference between the vapor and liquid must be greater than 1.0%.
Operation of the Model 187 near the critical point of cryogenics
(where the dielectric of the vapor
≈
dielectric of the liquid) is not
recommended.
5.2.4 The Model 187 displays “Max Diel Exceeded”.
1. The maximum dielectric has been exceeded for at least one sensing
element. The maximum allowable dielectric value is recorded on
the first page of this manual. If the dielectric of the media in which
any of the sensing elements is submerged exceeds the maximum
allowable value, the measurement section of the Model 187 may
become saturated and accurate measurements cannot be obtained.
2. If a sensing element is shorted, this can also result in the “Max Diel
Exceeded” error. Contact an AMI Technical Support
Representative for assistance in determining which sensing
element may be shorted. Moisture present on the sensing element
or in the BNC connectors can also cause a shorted condition.
A pack of non-conductive electrical connection lubricant (ECL) has
been included with the liquid level sensor to reduce the possibility
of moisture in the BNC connectors. Apply a small amount of ECL to
any of the BNC connectors that may be exposed to moisture. Mate
the doped connectors then remove any excess ECL from the outside
of the connector. Added protection can be achieved by covering the
doped connections with a short section of heat-shrink tubing.
Note: MSDS sheets for the ECL are available upon request.
5.2.5 The liquid level unexpectedly drops rapidly as the tank level
approaches 100%.
1. The vapor reference plate sensor is most likely becoming
submerged in liquid. Verify that the upper limit of the measured
span does not exceed the lowest point of the vapor reference plate
sensor (see “Configuring the Length Settings” on page 14.) and
lower the liquid level if necessary.