American Magnetics 187 Self-Compensating Liquid Level Controller - Manual (Page 13)

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Introduction
Model 187 Features
1.1.3 Convenient display and direct keypad entry
The instrument is equipped with a 16 x 2 backlit character-mode LCD
display which provides liquid level and setpoint indication in inches,
centimeters, or percent as selected by the user. A front panel keypad
interface allows the user to easily view and modify the instrument
settings. The default display indicates liquid level and fill/loss rate. The
current liquid level is updated and visible in many of the display modes
used in configuring various settings of the instrument.
The 4 x 4 keypad is provided for direct entry of values for setpoints, sensor
lengths, and other functions. The keypad also provides a convenient menu-
type interface for configuring various instrument settings that require
selection from a list of options.
1.1.4 Automatic level control
The Model 187 provides four level setpoints, two of which (A & B) are
control setpoints used to control liquid level through use of a solenoid-
operated fill valve. The remaining setpoints (HI & LO) are alarm setpoints
and can be set for other control or alarm functions.
The HI and LO setpoints operate relay contacts in addition to the front
panel LED indications. LED indication is also provided for the A setpoint,
B setpoint, and automatic controller (FILL) function of the instrument. All
setpoints are accessible via the keypad. The automatic controller (FILL)
function can also be manually overridden or disabled using the keypad.
A timeout feature is also provided with the automatic controller (FILL)
function. The timeout specifies the maximum amount of time necessary for
the Model 187 to fill the target vessel to the A setpoint. If fill is not
achieved within the timeout period, the Model 187 ends the fill operation
(de-energizes the rear panel controller output) and indicates expiration of
the timeout feature by blinking the FILL LED and setting the appropriate
flags accessible through the serial or GPIB remote interfaces.
1.1.5 Remote computer monitoring or controlled operation
The Model 187 can be configured to provide an optional analog 0-10 volt
DC signal accessible from the rear panel of the instrument for use with a
recorder. A 4-20 mA current loop option is available in lieu of the voltage
signal.
RS-232 is provided as a standard digital interface for the Model 187.
Additional digital interface options, including RS-422 or GPIB (IEEE
488.2 compliant), are available. The serial and GPIB remote interfaces
provide a comprehensive command set for monitoring and configuring all
functions of the instrument.