The Method Of Hogwash Oil Dual-Channel Detection Based On Digital Lock-in Amplifier

With the rapid development of China’s economy and society, The demand of oil is increasing. But, there are frequent incidents of hogwash oil in recent years, it has become a big challenge to our national food safety. A variety of toxins in the waste oil seriously overweight, the long-term intake may even become cancerous incentives. There are several detecting methods currently:determination of water content, determination of acid value, cholesterol content assay and determination of the heavy metal content etc. This paper introduces a new dual-channel detection method based on digital lock-in amplifier.This paper introduces the basic principles of the lock-in amplifier detection and correlation detection firstly, and verifying the effect of the correlation detection by Matlab simulation. Then, analyzing the structure and advantages of digital lock-in amplifier, and introducing the design of digital lock-in amplifier based on DSP chip TMS320F2812from both software and hardware. Doing experiments with this digital lock-in amplifier, the conductivity of water-washed oil and water are detected at the same time, difference of the two as the final result.The results of experiments show that all the conductivity of qualified samples’ conductivities are less than10μS/cm. This detection method can effectively avoid the interference from the conductivity of the water. The detection method is proposed in this paper is preliminary study for the oils conductive characteristics, it’s also has limitations in practice. Detection error is large when samples contain less waste oil, also need to complement other detection methods to get accurate results.