At present, the portable instruments for radon measurement are poor measurement sensitivity, large volume and high power consumption. On the basis of the passive indirect measurement method, Au-Si surface barrier detector, charge sensitive preamplifier and main amplifier were integrated, and a high resolution narrow pulse peak hold circuit was designed successfully. With small volume and low power consumption, the part of data processing and control, based on the mixed-signal system, can make field analysis, field print, data uploading and so on. The calibration was made using the calibration method of unsteady concentration, and the results showed that this instrument is evidently better than MODEL1027 of USA in standard deviation of coefficient.
