FAQ Sensors


How do we need to handle SQUID sensors?

The SQUID should never be subjected to a current larger than 100µA at room temperature. Please check the measurement current from an Ohmmeter before connecting to the SQUID. Do not use the Ohmmeter with automatic range selection.

The SQUID is an ESD (electrostatic discharge) sensitive device. A permanent damage may occur on devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

Overheating during soldering may result in drastic change of the SQUID characteristics or loss of functionality. Recommended soldering time is not more than 1sec (soldering temperature <300°C) with interval at least 10sec between soldering.

How does a SQUID sensor work?

SQUID schematisch Using Superconductivity we can design the world most sensitive sensors, so called SQUIDs. Squid is commonly known as a group of marine cephalopods with eight arms and two tentacles but in the following we will use it as the acronoym for (Superconducting Quantum Interference Device). Every SQUID consists of a macroscopic superconducting loop with one or two weak links (Josephson Junctions). When cooled below the critical temperature the magnetic flux will be trapped in the loop. The super current (isupra) causes the magnetic flux to be a multiple of the fluxoid Φ0. When Φ0 changes the superconductor adapts isupra to compensate the total flux. Now the weak link comes into play. Isupra can not compensate large changes in the external magnetic Φextern. When the critical current IC of the weak link is surpassed superconductivity break down locally and a flux quantum can enter or leave the superconducting ring. This crossover happens instantly and is accompanied by energy dissipation because the weak link is in a resisitive state. This dissipation can be accounted for very sensitively. This is the basic concept of a SQUID sensor.

Supracon is one of the few commercial suppliers of this sensor type in the world.

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