Simulation of differential capacitive sensor can measure the displacement (rotation)

      The test is capable of measuring differential capacitance displacement sensor simulation, circuit simulation experiments by sinusoidal excitation circuit, the bridge circuit, an amplifier circuit, a rectifier circuit and smoothing circuit composed of five parts. Applying a sinusoidal excitation signal power bridge, when the intermediate differential capacitance in the equilibrium position of the movable piece, the conversion bridge output is zero, when a certain displacement of the movable piece, the bridge out of balance conversion circuit, a voltage output value, this voltage signal is very small, the extracted and amplified, rectified, filtered DC component of the differential capacitance is proportional to the displacement of the movable piece.

Three: circuit design and simulation results

（1）

Figure 2: Schematic Circuit

Figure 3: Schematic sinusoidal excitation signal, and an output waveform

 

                  Figure 4: a partial schematic electrical bridge sensor and the output waveform of FIG.

From the above simulation results when the sensor of FIG two capacitors are equal, i.e., when the bridge is balanced, the output is almost zero.

          Figure 5: Simulation results when the bridge imbalance

When the bridge is unbalanced, the measured capacitance value C _{. 3} = 40nF, C _{. 4} = 60nF when a waveform, as shown in FIG.

Were measured at C3 = 30nF, C4 = 70nF, C3 = 20nF, C4 = 80nF, C3 = 10nF, C4 = 90nF output in these four cases, the output voltages are found in mV.

   Figure 6: an enlarged circuit diagram of an output waveform, and

  After the bridge output signal is amplified ten times, as shown in FIG.

               Figure 7: Schematic rectifier circuit and the output waveform

 

                Figure 8: Schematic filter circuit and the output waveform

 

Seen from the figure, after such filtering circuit through the AC component is significantly reduced, the waveform gently. Were measured using a voltmeter C3 = 50nF, C4 = 50nF, C3 = 40nF, C4 = 60nF, C3 = 30nF, C4 = 70nF, C3 = 20nF, C4 = 80nF, C3 = lower 10nF, C4 = 90nF five cases of data and records.

Table 1: output voltage of five cases

Displacement Δ	0	10	20	30	40
C3, C4 (NF)	50,50	60,40	70,30	80,20	90,10
The output voltage	2.077mV	-220.555mV	-586.08mV	-968.079mV	-1.348V

（2）由统计的仿真结果可知，输出的电压与电容成线性关系，进而与位移成线性关系。结果中负号表示方向沿使C3两极板距离减小的方向运动。

四：结论

本次试验设计了一种差动电容式位移传感器,主要对差动电容式位移检测电路进行了仿真研究。其中检测电路设计主要包括正弦激励电路、电桥电路、放大电路、整流电路和滤波电路。最后利用Multisim软件对所设计的系统进行仿真,并分析了传感器性能。仿真研究表明,检测电路具有合理性,输出电压和位移有间接的线性关系，测量范围内具有很好的线性度。