A Magnetometer Based On NMR

The theory of nuclear magnetic resonance (NMR) was born in 1946, and it is quite mature after 60 years of development. It can be used to establish the magnetic field parameter natural benchmark based on atomic constant, and has many unmatched advantages, such as the high precision, strong anti-interference ability and good stability, in measuring the magnetic induction. The text introduces the theory of NMR and the design of a digital benchmark magnetometer based on NMR. The paper expounds the design of the software and hardware in the control and display part of the magnetometer.The system takes the marginal oscillator and pick-up circuit of the NMR signal as its core. In order to save time, the instrument takes a Hall effect device to estimate the magnetic induction, and chooses the measuring gear. Then it takes a single chip microcomputer to control the D/A converter, and adjusts the frequency of the marginal oscillator by changing the reverse bias to the varactor diode, and so it can realize the automatic search for the NMR signal and autotracking it. Finally, the instrument takes CPLD and single chip microcomputer to measure the frequency of the marginal oscillator, changes it into the magnetic induction based on Larmor precession formula, and shows the measuring result and NMR sketch map on liquid crystal display (LCD).The design ensures the reliability of the product by the power supply, the design of circuit and printed circuit board (PCB). The measurement range is 0.1T～2T, and the measurement precision is 10-5～10-6. The paper also carries on a further discussion about the theory of marginal oscillator according to the experimental facts.The instrument is small size, light weight, low cost and simple operation. Experiments show that it has a high measurement precision and speed, and is suitable for magnetic field measuring benchmark.