Abstract: In order to realize and improve the technical indexs of infrared oil content analyzer，a new design of signal conditioning circuit in infrared oil meter is presented． The signal conditioning circuit combines the phasesensitive
detection circuit composed of analog switches with the dual-channel ideal integrator，which can improve the signal-to-noise ratio and speed up the scanning speed of the spectrogram． The control signal of the system is realized by LPC2136 chip of AＲM7 series． The circuit is suitable for processing output voltage signal converted from optical signal through sample cell，pyroelectric sensor，pre-amplification and filtering in infrared oil content analyzer． Experiment results show that the scanning speed and accuracy of the oil content analyzer have been improved． The experimental results verify the reliability and effectiveness of the circuit，and the optimization of the signal conditioning circuit of the infrared oil content analyzer．

Key words: infrared oil content analyzer, phase-sensitive detection, ideal integrator