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.

High and Low Alarm Functions

The Model 185 uses capacitance-based level sensing . Two independent "High" and "Low" alarm setpoints activate front panel LED warning indicators and rear panel relay outputs in the event of an overfill or liquid loss condition. The "Low" level alarm also energizes an audible warning which is silenced from the front panel. Alarms are front panel programmable from 0 to 100 percent of the active sensing length.

Convenient Display and Simple Calibration

The instrument is equipped with a 4-digit LED display which provides liquid level indication in inches, centimeters, or percent as selected by a front panel switch . A front panel switch allows the user to easily adjust the instrument's length setting for a specific active sensor length. The sensor active length can be entered in either inches or centimeters. More information about simple calibration can be read here .

Remote Monitoring and Control

The Model 185 can be provided with an optional 0-10 volt DC signal on 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. Computer interface options, including RS-232 Serial Port/Data Logger or IEEE-488 , are also available.

View the Model 185 Manual ( Technical Support page )

Model 185 Specifications (at 25 °C)

Level Measurements
0.1%, 0.1 cm, or 0.1 in
± 0.1 %
Maximum Length Readout:
650.0 cm (255.9 in)
Operating Parameters
HI and LO Alarms:
0% to 100% adjustable
HI/LO Alarm Relay Contact Ratings:
30 VAC or 60 VDC, 10 VA (up to 0.5 A max)
[normally open, closed on alarm]
0-10 Volt Analog Output
Integral Non-linearity:
± 0.012 %
16 bits
Total Error:
± 1.1 %
Voltage Drift (0-10 V):
100 ppm  / °C
Maximum Load:
4 mA (2.5 kW @ 10 V output)
4-20 mA Analog Output @ 24 V
Vext Supply Range:
13-32 VDC
Voltage Compliance:
Vext - 3.5
Integral Non-linearity:
± 0.012 %
16 bits
Total Error:
± 0.25 %
Current Drift (4-20 mA):
75 ppm  / °C
10 mA / V
Power Requirements
90-132 VAC or 180-264 VAC 50-60 Hz, 
30 VA
Dimensions (Standard):
97 mm H x 213 mm W x 282 mm D
(3.8" H x 8.4" W x 11.1" D)
Weight (Standard):
1.6 kg (3.6 lbs)
Dimensions (Rack Mount):
89 mm H x 483 mm W x 282 mm D
(3.5" H x 19" W x 11.1" D)
Weight (Rack Mount):
2.0 kg (4.3 lbs)
Ambient Temperature:
Operating: 0 °C to 50 °C (32 °F to 122 °F)
Non-operating: -20 °C to 60 °C (-4 °F to 140 °F)
Relative Humidity:
0% to 95%; non-condensing


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