American Magnetics 286 Multi-Sensor Liquid Level Instrument (CE-Marked) - Manual (Page 15)

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1 Introduction
1.1 Model 286 Features
The American Magnetics, Inc. (AMI) Model 286 Liquid Level Controller is
a microprocessor-based instrument designed to provide multiple sensor
capacitance-based monitoring and control of liquid levels. In addition to
the brief feature descriptions provided below, a detailed feature matrix is
provided on page 54.
1.1.1 Capacitance-Based Level Sensing
A typical control system consists of a Model 286 Liquid Level Controller,
up to four AMI liquid level sensor(s), and connecting coaxial cable(s). The
primary instrument sensing element is typically a 3/8 inch (9.5 mm) OD
concentric-tube cylindrical capacitor constructed of stainless steel which
allows the fluid to become the dielectric between the concentric cylinders.
The instrument measures the sensor capacitance, which is directly related
to the percentage of the sensor immersed in the liquid.
1.1.2 Multiple Sensor Monitoring and Control
The Model 286 is capable of monitoring four independent, capacitance
level sensors and controlling liquid level in up to two vessels by directly
controlling the actuation of two solenoid-operated flow control valves.
1.1.2.1 Factory calibrated
The Model 286 is typically calibrated by AMI for matched sensors
in liquid nitrogen, and is ready for immediate use upon delivery. If
the working fluid is something other than nitrogen, an approximate
calibration can be performed or the customer must perform an open
or closed dewar calibration after installation when the sensor can
be immersed in the target fluid.
1.1.2.2 Multiple calibrations per sensor
Each of the four sensor inputs to the Model 286 can have up to four
independent calibrations, which are user-selectable. The user
simply selects the desired calibration using the menu-type
interface. All calibration data is passcode protected and stored in
nonvolatile memory.
1.1.3 Convenient Display and Direct Keypad Entry
The instrument is equipped with a 16-character x 2-line backlit character-
mode LCD display which provides liquid level and setpoint indication in
inches, centimeters, or percent as selected by the user. The default display