Highly Sensitive Measurement of Moisture Content Using HTS-SQUID
We developed a highly sensitive magnetic system for measuring moisture content using an HTS-SQUID sensor. The system consists mainly of an exposure coil, a Dewar flask containing HTS-SQUID immersed in liquid nitrogen, a cancellation coil, a lock-in amplifier, magnetically shielded box, and FLL circuit. The cancellation coil was used to eliminate the applied magnetic field at the sensor position, and then a cancellation ratio of more than -40 dB was obtained. By the high performance, the subject can be exposed to a powerful magnetic field strength in the order of muT, and a weak magnetic signal of less than tens of pT from the subject can be detected. Using a magnetic vector analysis technique, more precise measurement of moisture content is realized.