AMI liquid helium (LHe) level sensors use small niobium-titanium (NbTi) wires as the detector element. A heater is created in which and helps to maintain the normal area of the wire in the portion above the LHe level, while the helium level in the portion of the wire below the liquid remains superconducting. The output voltage of the sensor varies linearly with the liquid level.
The AMI LHe level sensor is designed to work with the AMI LHe level meter. Operation of the sensor with other level instruments or different lengths of sensor with instruments calibrated for different lengths may cause the sensor to fail.
Standard rigid 4.2K LHe level sensors are typically painted gold. 2K LHe level sensors are painted red. 2K operation using a factory-configured AMI Model 1700 instrument for 2K operation or a Model 1740 dual-channel LHe level meter that can be set to 2K for operation by the customer.AMI cannot guarantee the accuracy or operability of 2K sensors for use with standard (non-2K) LHe level meters.2K LHe level sensors can be used in a wide variety of applications.
AMI manufactures a radiation resistant level sensor for high levels of area ionizing radiation. These special LHe level sensors will utilize Phosphor Bronze (PhBr) due to the fact that radiation can damage the insulation of PTFE wire over time.
PhBr wire also provides the lowest level of backup LHe loss because of the high thermal conductivity of PhBr wire compared to copper (Cu).