Design of signal conditioning circuits for impedance detection of milk bacteria

The impedance method detection of milk bacteria requires a high quality signal. In order to meet the requirement, a complete signal conditioning circuit is designed and analysised in this paper. Firstly, Biological signals can be reflected in form of electrical signals by impendance sensor. Secondly, In order to detect weak signals in noises. I have designed Preamplifier circuit, Low-pass filter amplifier circuit, Modulate and Demodulate Circuits. At last, Mathematical models are established after comparison test and the theory analysis. Experimental results show that the signal conditioning circuit can effectively improve SNR, and the sensor output signal can be amplified between 0 and 5V. The system can provide reliable signals for upper computer and display system.