High precision isolation amplification instrument for geophysical exploration
地球物理勘探用高精度隔离放大器

A high precision isolation amplifier for front-end electrical filed conditioning and sampled current signal isolation amplification is introduced. The instrument is composed of the input buffer circuit, the first stage amplifier and the low-pass filter with gain as 0 dB, 10 dB, 20 dB, 30 dB, the second stage amplifier and the low-pass filter with gain as 0 dB, 10 dB, 20 dB, 30 dB, the third stage amplifier and the low-pass filter with gain as 0 dB, 10 dB, 20 dB, 30 dB, the isolation stage with high linearity, high precision isolation amplifier AD202, the output stage with low-pass filter, gain control circuit, and overload detection and indication circuit. It offers a total gain the 90 dB; ensures proper amplification of small signal less than 100 uV. To test the instrument, the small signal input test, the frequency response test, and the non-linearity test and drift test are carried out. Test results show that the maximum nonlinear error of the isolation amplifier based on AD202 and LT1250 is 0.23%. Its drift is 37 uV in 19 hours, reacheing the requirement of the design.