“In the field of radiological diagnosis, researchers have designed low-noise amplification circuits and high-precision signal acquisition circuits, successfully developed weak current measurement circuits, and achieved weak current measurement of 20 fA~10 μ A. A prototype device of capacitance integral radioactive activity meter was built by combining a well type ionization chamber. The test results show that the repeatability of the device is basically consistent with the performance of the commercial RM-905A, with a background of less than 0.065 MBq, repeatability not exceeding 0.84%, and instability of 1.94%.”