Magnetic flux measuring apparatus by hysteresis characteristic type digital FLL using counter system for squid

A magnetic flux measuring apparatus which measures a magnetic field in accordance with an FLL system by using a SQUID for generating a voltage that periodically fluctuates at a period of a magnetic flux quantum Φ0 on the basis of an increase of a magnetic field, the apparatus comprising:

• an amplifier which amplifies a periodic output voltage from the SQUID, and outputs an amplified analog signal;
• an AD converter which converts the amplified analog signal to a digital signal;
• an integrator which, on the basis of an output of the AD converter, generates integral data that corresponds to a magnetic flux change component from a predetermined lock point for each period, lock points sequentially shifting to next lock points if the magnetic flux exceeds control ranges corresponding to the lock points, the integrator being controlled to be reset;
• a change rate counter which is connected to the integrator and counts the number of the resets;
• a data merge unit which merges the integral data and data on the number of resets;
• and
• a data demerge unit which receives merged data transmitted from the data merge unit via a predetermined transmission channel, and demerges the merged data into the integral data and the data on the number of resets;
• a reproducing counter which counts a frequency that corresponds to a magnetic flux to be measured, based on the demerged data on the number of resets;
• and
• a data reproducing unit which measures a magnetic flux value on the basis of data for the integrator and the counted frequency.