An automatic gain linear micro-current measurement circuit applied in Langmuir probe

Langmuir probe is an important instrument for detecting space plasma, used in sounding rocket project in Meridian as one of payload at present. This article describes the automatic gain linear micro-current measurement circuit used in Langmuir probe, which can linear measure tiny current between 50pA to 500uA in multi-gain range. Its working principle is that firstly the circuit real-time monitors and identifies the output signal, then adjusts automatically the gain to match input current according to the identified results, to achieve the micro-current measurement accurately. The circuit obtains excellent measure data in the lab tests.