Liquid Helium Level Monitor

Listing ID #3939451

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Supply Type Manufacturer, Exporter, Supplier
Preferred Buyer Location All over the world

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Product Details

The Model 135 is an advanced liquid helium level monitor which incorporates AMI's patented sample-and-hold design with automatic helium level sensor vacuum burnout protection. The Model 135 is ideal for operation in systems where it is important to monitor the liquid helium level while also minimizing the helium losses. 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 135 adds "High" and "Low" alarm setpoints which activate front panel LED warning indicators and rear panel relay outputs in the event of an overfill or liquid loss condition. The alarms also energize an audible warning which can be silenced from the front panel. "High" and "Low" setpoints are programmable from 0 to 100 percent of sensor active length.

Minimal liquid helium losses

In order to minimize liquid helium loss, the Model 135 automatically energizes the liquid helium level sensor at user programmable time intervals and monitors the normal (resistive) zone as it progresses from the top of the sensor toward the liquid surface. As soon as the normal zone reaches the liquid surface, the level reading is saved and the current in the sensor is turned off until the next sample interval occurs. An LED sensor current indicator is illuminated during each sample. Sample intervals are user programmable from the front panel and can be set between "0.0" (continuous reading) to "600.0" minutes or hours. A manual update switch provided on the front panel can also be set to obtain continuous readings during a helium transfer period or to manually force an immediate measurement.

Sensor burnout protection

The Model 135 provides automatic helium level sensor vacuum burnout protection. A liquid helium level sensor energized in a vacuum environment will self-heat to the point of burnout within seconds. AMI’s innovative microprocessor-based circuitry detects incipient sensor burnout and de-energizes the sensor before damage can occur. A 5% increase in sensor resistance will trigger this protection, causing the current to be switched off for 6 seconds before attempting to resume normal operation.

Convenient display

The Model 135 is equipped with a 4 digit LED digital display which provides liquid helium level indication in inches, centimeters, or percent as selected by a front panel switch. Front panel sensor calibration allows the user to calibrate the instrument quickly and easily for any length sensor. Calibration can be performed in either inches or centimeters of sensor active length with automatic reading crossover between inches, centimeters, and percent.

Company Details

The rated field of each AMI magnet is the field at which the magnet can be operated continuously when immersed in liquid helium at a maximum temperature of 4.2K. Quench fields exceed the rated field in all cases. All standard magnets are tested by AMI in excess of the rated field. Warranted performance at lower temperatures and higher fields can be supplied on special order. Protection from damage in the event of a quench at fields up to and including the rated field is assured by the design and construction of the magnet. Each magnet is warranted against such damage by the standard AMI warranty.
All quoted currents are nominal and may vary slightly from the cited currents in the final magnet. The coil constant which specifies the magnetic field produced per ampere of current is supplied with each magnet. This constant is determined analytically for lower-homogeneity magnets, or by NMR measurements for high-homogeneity magnets.
Persistence of the magnetic field in the persistent mode varies with the inductance of the magnet and the conductor used in its construction. Guaranteed quotations can be provided upon request.
Homogeneities are specified as the maximum deviation from the central field at any point in the specified volume, and are usually quoted over a 1 cm diameter spherical volume. Where required, the homogeneity is verified using a 3 mm diameter NMR probe moved throughout the homogeneous volume.