The new Model 1800 Liquid Level Instrument
- two independent auto filled dewars
- Pre-Cool mode for long transfer lines
- Auto changeover control
The American Magnetics, Inc. (AMI) Model 185 Liquid Level Instrument (cryogen monitor) system is an advanced, microprocessor-based solution designed to provide accurate and reliable level monitoring of virtually any cryogenic liquid. Microprocessor-based electronics provide 0.1% readout accuracy. Nonvolatile, read only memory maintains instrument calibration without battery backup. Watchdog timer circuitry and low line voltage (brownout) detector prevent microprocessor lock-up and
provide fail-safe Operation.
The American Magnetics, Inc. (AMI) Model 186 Liquid Level Controller includes all the functions of the Model 185 plus a level-control capability. The Model 186 Liquid Level Controller (cryogen monitor) system is an advanced, microprocessor-based solution designed to provide accurate and reliable level monitoring and control of virtually any cryogenic liquid. Microprocessor-based electronics provide 0.1% readout accuracy. Nonvolatile, read only memory maintains instrument calibration without battery backup. Watchdog timer circuitry and low line voltage (brownout) detector prevent microprocessor lock-up and provide fail-safe operation.
A typical control system consists of a Model 286 Liquid Level Controller, up to four AMI capacitance-based liquid level sensors, 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.
Multiple Sensor Monitoring and Control
The Model 286 is capable of monitoring four independent, capacitance level sensors or controlling liquid level in up to two vessels by directly controlling the actuation of two solenoid-operated flow control valves.
The Model 286 is typically calibrated by AMI to mated 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 may perform a calibration after installation when the sensor can be immersed in the target fluid.
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.
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 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 length, 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.
Two user-defined setpoints, HI and LO, are provided for all four channels with front panel LED indications for Channels 1 and 2. The HI and LO setpoints may also operate two pairs of low-current, rear panel relay contacts and a built-in audible alarm. The HI/LO relay contact pairs may be assigned to Channels 1 and 2, or to Channels 3 and 4.
The Model 286 provides three controller modes: normal, auto-changeover, and pre-cool. The desired mode can be selected via the front panel keypad or remote interface. The level control sequence varies based on the selected mode. See the discussion provided in the Model 286 Manual at AMI's Technical Support page or the Model 286 Brochure for more information about the controller modes.