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.

Automated fill and alarm functions

The Model 186 uses capacitance-based level sensing. Fill control and alarm functions are provided, front panel programmable from 0 to 100 percent of the active sensing length. Two independent control band setpoints, "A" and "B", activate a power receptacle on the rear panel. When the liquid level drops below the "B" setpoint, the power receptacle is energized and remains energized until the liquid level rises to the "A" setpoint. The Model 186 also provides a fail-safe timer feature that automatically de-energizes the power receptacle once a user programmed maximum time interval of up to 600 minutes is reached.

The Model 186 also provides "High" and "Low" alarm setpoints to activate front panel LED warning indicators and rear panel relay outputs (for remote alarming) in the event of an overfill or liquid loss condition. The "Low" level alarm also energizes an audible warning which can be silenced from the front panel. The Model 186 is ideal for unattended systems where automated fill is required.

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 186 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 186 Manual (Technical Support page)

Model 186 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]
A and B Control Setpoints:
0% to 100% adjustable
Controller Output:
AC line voltage @ 2A max current
Fill Timer:
0.1 to 600.0 minutes
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, 
2.2 A
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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