Hartley eddy current sensor used in maglev molecular pump

For the displacement sensor used in maglev molecular pump in the industrial field, in addition to good static characteristic and high dynamic characteristic requirements, its volume also affects the pumping speed, the vacuum and the compression ratio of the maglev molecular pump. Aiming at the high-vacuum maglev molecular pump, a design method of the eddy current displacement sensor (ECDS) based on the Hartley oscillator was proposed. The symmetrical probes were connected into the same oscillation circuit as working inductors. Then the dynamic characteristic of the ECDS was analyzed in detail. And a method to compensate the response bandwidth without affecting the sensitivity and the linearity was put forward. Experimental results indicated that in the measurement range of -0.4-0.4 mm, the linearity came to ±1.17% and the sensitivity achieved 9.901 mV/μm, the resolution was ±0.25% and the response bandwidth was 10.2 kHz. The volume of the integrated circuit board of the two radial four-way displacement signal was only π×4² cm², which greatly reduced the sensor volume. It can satisfy the requirements of the maglev molecular pump for higher pumping speed and higher vacuum.