Wireless Single-Chip Capacitance Sensor For Small-Distance Measurement

Capacitive displacement transducer is a kind of non-contact measurement instrument. Compares to The general displacement measuring instrument,it has simple structure and high resolution and measurement range. Now, micro displacement capacitance sensor is not easy to be detected accurately, Because of its smaller capacitance value. And the traditional wired measurement method has also limited the scope of its application. For solving the above problems,The paper introduces the development of a wireless chip micro displacement capacitance sensor. And to further improve the practicality of micro displacement capacitance sensor.This paper introduces the common types of displacement sensor, its characteristics and applicable scope.,studying the basic principle of capacitive displacement sensor probe, high performance monolithic double interdigitated electrode is choose to be the Probe micro displacement capacitance sensor. In order to measure micro displacement capacitance sensor values accurately, Comparative study of all the capacitance detection method.The research has identified AD7745detection chip as the capacitance measurement circuit core.ZIGBEE has the characteristics of chip embedded with8051nuclei, Also contains a IEEE802.15.4compatible wireless transceiver, high reliability, low price etc.Using ZIGBEE’s characteristics to develop a wireless data transmission system. The system can complete the Acquisition, transmission, reception function of the capacitive displacement sensor capacitance.Using the VC++MFC tool develop the PC software.it adopts serial port to receive the capacitance data, perform data processing, draw a one-dimensional coordinate system, Display the current displacement of the metal.Building the experimental platform, acquire capacitance between the metal plate and the sensor range of25mm sensor. The sensitivity of the sensor in the25mm range were analyzed, In order to calibrate displacement measuring system, To linearize the data segment in the6mm displacement sensitivity higher capacitance. When using the Unsegmented for data processing, Data linearity is0.8989. When using the segmented, Linearity of three segments of data are respectively0.9951,0.9900,0.9895.Finally, the experimental results show, Wireless micro displacement capacitance sensor is developed in this paper has the measurement range of6mm,0.1mm resolution, measuring relative error is less than1.2%, the communication distance is more than50m.