差拍法在油水浓度自动检测中的应用

提出了一种利用差拍法测量油水浓度的有效方法。将油水浓度的变化转换为电容器容值的变化，继而利用标准正弦振荡电路将容值变化转换为振荡频率的变化。通过与固定振荡频率的信号进行混频、低通滤波得到差频信号来反映油水浓度的变化。实验结果表明，该测量系统可检测到0．02％的油水浓度的变化，并且具有较高的稳定性。

Automatic Measurement of the Concentration of Oil and Water Mixture Using Heterodyne Frequency Method

An efficient heterodyne frequency method to measure the concentration of oil and water mixture is proposed. The change of concentration of the oil and water mixture can be represented by the change of the capacitance value. Then we use a standard sine wave oscillator circuit to convert the capacitance change into the frequency change. The frequency signal is mixed with a fixed frequency signal, and goes through a low-pass filter. After this process, we get the heterodyne frequency which indirectly represents the concentration change of the oil and water mixture. It indicated from the experiment that the sensitivity of the system is 0 02%, and it has much higher stability.