LC3 Liquid Nitrogen Level Controller

The Teragon LC3 controls and monitors the level of liquid nitrogen in dewars and cold traps. Its unattended operation keeps your cryogenic reservoir filled - automatically and reliably - without the hazard of manual transfers. The front panel continuously displays the current liquid level and loss rate. Applications include foreline traps, radiation detectors, cold fingers and cryopreservation.

The controller monitors the liquid level with a capacitive probe (model LP3) which is sensitive to the different dielectric constants of liquid and gaseous nitrogen. Probes are assembled to customer specification and are available with sensing lengths from 4 inches to 10 feet. The controller has four user defined setpoints: low-level-alarm, low-level-fill, high-level-stop and high-level-alarm. These setpoints are entered from the front panel of the controller and no manual adjustment of the LP3 probe is necessary.

The LC3 maintains the liquid level between the user defined setpoints using "on/off" control. When the nitrogen level drops to the low-level-fill setpoint, a relay is energized to actuate a fill valve. The relay remains energized until the liquid level reaches the high-level-stop setpoint. The alarm will sound if the level is ever outside the range defined by the high and low alarm setpoints.

The controller comes equipped with a noise free, zero-crossing solid state relay which can be used with internal or external power. A manual override allows instant control over the fill operation. The controller's RS-232 serial interface permits remote monitoring and control. Virtually all keypad commands can be issued via the serial interface.

The LC3 high-reliability features include an internal watch-dog timer, non-volatile memory and a fail-safe alarm relay. The relay can be used to activate an external alarm, an auto-dial phone system, or to remove the high voltage bias from radiation detectors. Connectors for the alarm relay, probe cable and solenoid output are provide on the controller's rear panel.

The LC3 controller comes with a power cord, solenoid cable, probe cable and user manual. LP3 level probes are sold separately. All parts are covered by a 1 year warranty. The LC3 is a durable unit designed for years of precise and reliable service. Inquiries regarding custom applications are welcome.

Standard features of the LC3 include:

	Continuous Monitoring: The LN2 level and rate of evaporation are continuously monitored and displayed on the front of the controller.
	User Defined Setpoints: The user defined setpoints (low-level-alarm, low-level-fill, high-level-stop and high-level-alarm) are entered from the controller's front panel.
	Adaptable Control: A solid-state relay is used to activate a cryogenic solenoid valve. The relay is jumper selectable to provide either 120VAC @ 2A directly from the LC3 or to act as a 12-120VAC switch for external power.
	Manual Override: A manual override button on the front panel allows instant control over the liquid nitrogen transfer process.
	Digital Precision: Using an embedded microprocessor, digital filtering is used to achieve a level precision of 0.1%. All setpoints are stored with this precision in non-volatile E2PROM memory.
	Serial Interface: The RS-232 serial interface allows remote monitoring and control. Virtually all keypad commands can be accessed via the serial interface and a keypad lockout feature is provided for added security.
	Multiple Alarm Signals: In the event that the liquid level exceeds either alarm setpoint (high or low), an audible alarm sounds and the display indicates a fault condition. A fail-safe alarm relay is provided to activate an external alarm or auto-dial phone system.
	Effortless Calibration: Probe calibration is quick and easy; with the dewar filled, press the FULL key. Remove the probe and press EMPTY. Calibration results are stored in non-volatile E2PROM memory.
	High-Visibility Display: The backlit, high-contrast display is visible with or without ambient light. The contrast is adjustable from the front panel to provide maximum visibility in any environment.
	Analog Output: An analog voltage, proportional to the liquid level, is provided on the back of the LC3. The 0-1 VDC range corresponds to liquid levels of 0-100%.

Specifications

LC3 Controller
Power: 120VAC @ 3Amps, 50-60 Hz
Fill relay: 120VAC @ 2Amps, Zero-cross switching.
Alarm relay: 0-120VAC @ 0.25Amps, Fail-safe operation is standard.
Analog Output: 0-1VDC @ 1mA max.
Serial Interface: 1200, 2400 or 9600 baud
Dimensions excluding tilt handle: 3.4 in. H x 7.5 in. W x 7.0 in. D (86 mm x 190 mm x 178 mm)
Weight: 2 lbs. (0.9 kg)

LP3 Level Probe
Probe Type: Capacitive transducer
Sensing Lengths: From 4 in. to 10 feet (100 mm to 3050 mm)
Wetted Parts: 316 Stainless Steel, PTFE & Epoxy
Probe Connector: Male mini-DIN-6

The LC3 controller comes with a power cord, solenoid cable, probe cable (6 foot each) and a user manual. A one year warranty covers all parts. Specifications are subject to change without notice.

Options & Accessories

100, 200, or 230VAC line power

Probe Mounting Adapters

Controller Rack Mounting

BNC Probe Connectors

Transfer hardware including cryogenic solenoid valves, plumbing, fittings, insulation, phase separators, etc.

Placing Orders

Please specify the required Sensing and Insertion Lengths as shown in the LP3 Probe diagram. The Sensing Length is the distance from the bottom of the probe to the vent. For proper operation the vent must be located within the LN₂ reservoir. The Sensing Length is the distance over which the liquid level ranges from 0% to 100%. The minimum Sensing Length is 4 inches (100 mm).

The Insertion Length must include the distance over which the temperature changes from ambient to cryogenic. Normally this includes the height of the dewar cap and any mounting fittings. The minimum Insertion Length is the Sensing Length plus 2 inches (51 mm). Note that the probe should not be mounted flush against the floor of the reservoir. A minimum clearance of 0.040 inch (1 mm) is required at the end of the probe to allow the liquid to enter.

U.S. Pricing

LC3 Controller: $695

LP3 Probe with Insertion Length up to 12 inches (305 mm): $295

For each additional inch (25 mm) of LP3 Insertion Length: $3

Optional Adapter (1/4" MPT to compression fitting): $15

Controller rack mounting (single or side by side): $100

Prices are FOB San Francisco and are subject to change.