American Magnetics 187 Self-Compensating Liquid Level Controller - Manual (Page 66)

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Service
Troubleshooting Hints
5.2.6 The liquid level unexpectedly rises rapidly as the tank level
approaches 0%.
1. The liquid reference plate sensor is most likely becoming exposed to
vapor. Verify that the zero offset does not fall below the highest
point of the liquid reference plate sensor (see “Configuring the
Length Settings” on page 14.).
5.2.7 The USER and FACTORY calibrations do not yield the same
liquid level.
1. It is possible that the USER calibration was not performed
properly. Review paragraph 3.3.11 on page 24 for the proper
procedure for a USER calibration.
2. If the installed length of cable from the Model 187 instrument to
the AMI sensor significantly exceeds 6 feet, an error of up to 5.0% is
within expected tolerances. In this case, the USER calibration is
more accurate than the FACTORY calibration. Please contact an
AMI Technical Support Representative for further information
regarding recommendations for a USER calibration.
5.2.8 The Model 187 is not responding to remote communications
commands.
1. Verify your communications cable integrity and wiring. See the
Appendix for RS-232/422 connector pinouts.
2. Check to make sure you are sending the correct termination to the
instrument. If you are using RS-232 or the RS-422 option, make
sure the baud rate, number of stop bits, and data bits/parity
settings match the setting of the host device. If you are using the
IEEE-488 option, check the primary address setting and make sure
the controller software is set to query the instrument at the
primary address selected.
3. Check your host communications software and make sure it is
recognizing the return termination characters from the instrument.
For RS-232 communication, the return termination characters are
. For IEEE-488, the return message termination
characters are with EOI.
4. If the instrument is responding repeatedly with errors, try a device
clear command (DCL) or powering the instrument off and then
back on. Be sure you are sending valid commands.
If you experience continued trouble with the IEEE-488 interface, you may
have an incompatible IEEE-488 card in your host computer. In the past,
AMI has found subtle differences between manufacturers of IEEE-488