A DPSD algorithm which doesn t require a reference signal of the same frequency is proposed in this paper.

Electrical impedance tomography(EIT) system must have the properties of high precision and speed,thus the digital phase-sensitive detector(DPSD) based on the field programmable gate array(FPGA) is developed for data collection of EIT.

Digital Phase-sensitive Detection Technology in Precision Inductance Sensor;

The weak signal acquisition under the strong noise interference was solved by the digital phase-sensitive detection technique,and an analysis model was built by means of the pr.

Through optimizing regulation circuits and applying modular function design based on multi-DSP,auto gain control,in-time calibration correction and digital phase-sensitive detection,the multi-channel and multi-frequency weak signals of MIT coils array may be acquir.

the measuring circuit of inductance sensor has been analyze,discussed the measure to level off the amplitude of sine wave generating circuit,introduce the method to improved the performance of measuring circuit by used digital phase sensitivity detection,and gave the data of static testing.

Then some techniques are combined to improve the measuring precision, such as the selffixed amplitude technique, waveformmending technique, full digital phase sensitivity detection technique, as well as digital filter and linearity compensation technique in the software.

This paper presents a new type of phase sensitive detector which consists of two sample and hold integrated circuits and a differential amplifier.

In order to solve the problems of distinguishing polarity of the electric field in atmospheric electric field exploration,a new phase sensitive detector is designed,which is composed of electro-optical switch,quad analog switch and amplifier.