| With rapid development of modem scientific technology, especially high-speed development of computer technology, not only real-time sampling and disposal of the data are realized, but also modem gas density monitor has entered small, handy and portable development phase.Based on the features of photoelectric formaldehyde detection principle and detecting beam of light, the signal condition circuit for photoelectric formaldehyde density measurement sensor has been designed, which is mainly composed of preposing amplifying circuit of photoelectric detector, narrow band active filter and precise AC signal- DC signal converter circuit. Because the equivalent net input signal designed for AC signal- DC signal converter circuit of OP07 operational amplifier is less than 0.3μV, the detection limit for the formaldehyde testing system is dropped and the material testing precision is improved. And the detection limit of formaldehyde density specified by the test for the system with the signal condition circuit is less than 0.01μg/5ml.The article is consisted of five parts, the first part is to explain the feature of photoelectric signal and signal sampling, the second part is to discuss measurement principle and composition of measurement device, the third part is to introduce the structure of signal condition circuit and working mode for each part of circuit in detail; the fourth part is to introduce the testing and analysis of signal condition circuit; and the fifth part is to prospect the system's better development foreground for real use as well as summarize the article and offer insufficiency.
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