Signal Conditioning Circuit Design for Micro Gas Chromatograph

Micro gas chromatograph (Micro GC) converts the content of separated gas to the electronic signal with two thermo conductive detector (TCD), one is for the reference gas, and another is for the sample gas. The signal conditioning circuit directly determines the performance of Micro GC. In this paper, we designed a signal conditioning circuit to restrain the high common voltage of 10 V and keep a very low noise after a detailed theoretical calculation, then converts the signal to digital signal with a 24-bit sigma-delta ADC from TI. After applied the new designed circuit, Micro GC has a very good performance so that its linear dynamic range is more than 10⁶. Additionally, the new signal conditional circuit solves the over-heat problem existed in older conditional circuit in Micro GC.