Wireless Measurement System Based On Nanocapacitance Sensor

At nanometer or even sub-nanometer scale,precise positioning measurement is the core of high-end technical equipment.Nano capacitance sensor has the advantages of high resolution,high bandwidth,superior dynamic response,so it is widely used in the field of precision measurement and control.In view of the inconvenience of wired transmission,wireless transmission has shown significant advantages,which indicates wireless capacitive sensors for nano-positioning are in urgent need of development.At present,most researches on wireless applications related to capacitive sensors are based on protocols such as Zig Bee and Bluetooth,and are oriented to static measurements with low accuracy,low bandwidth,low speed,and poor real-time performance.Therefore,according to actual project requirements,the purpose of this paper is to design a set of high-precision,high-speed,high-bandwidth,and low-latency wireless systems for real-time nano-positioning measurement based on nano-capacitance sensors.The main research work is as follows:(1)Firstly,This paper discusss the mechanical and electrical structure of the nanocapacitance sensor.Then compared with the short-range wireless protocol Bluetooth,Zig Bee and UWB,Wifi protocol is selected to meet the high-speed dynamic measurement.wireless network protocol firmware and module system program of the radio frequency module are compiled based on the IDE development platform of Windows/Cygwin/Eclipse,Completing the Wifi protocol firmware burning of the wireless module and the configuration of the module system parameters,working mode,and network parameters.Finally,the wireless local area network between the lower computer and the upper computer is built,and the data and control instructions between them are transmitted wirelessly.(2)Aiming at the design index of wireless sensor measurement system,the overall system framework,hardware modules are designed and analyzed.This system selects following components,a nano-capacitance sensor probe with a measuring range of 100?m and a resolution of 0.5nm Hz^-1/2,a STM32F103 controller,a 24-bit ADS1256 as analog-to-digital conversion chip and the ESP8266 as Wifi radio module to wirelessly transmit the data and instructions.After that,the circuit schematic diagram is designed and the pcb acquisition board is made Completing signal acquisition and conversion.(3)The computer software and display interface are programmed using labview.At the same time,the communication instructions between the upper and the lower are designed and formulated,including controlling the hardware system parameters,working mode,network connection configuration,data processing and storage,etc.,so as to complete the real-time display of the position measured by the sensor.(4)The experimental test system of wireless nano-capacitance sensor is built to realize the signal acquisition and processing,wireless transmission and terminal interface display of the sensor.The system performance index parameters are tested as follows.Before all others,the main components of the system are tested.The accuracy of the sensor is tested getting static rms resolution is 0.4nm,peak-to-peak resolution is 1.2nm(noise-free resolution),which indicates that the sensor can accurately measure the displacement more than 1.2nm.The accuracy of the ADS1256 analog-to-digital conversion chip is tested by converting the reference voltage obtaining that the voltage jitter is within 6?V at 100 sps and ADC can measure the minimum displacement output of the sensor.The piezoelectric displacement platform is tested by applying step signals of different amplitudes through the controller.The piezoelectric ceramic pushes the hinge mechanism to move achieving a displacement resolution of more than 5nm,which indicates the accuracy of the sensor and ADC can meet the measurement requirements.Finally,wireless test of the system is carried out.The nano-piezoelectric platform is controlled to perform sinusoidal frequency sweeping motions of different frequencies.The nano-capacitance sensor feedbacks in real time to wirelessly transmits signal to computer displaying the position information.In this process,the wireshark tool is used to perform data statistical analysis on the wireless data packets.The experimental results show that there is no packet loss error in wireless transmission,the transmission distance is more than 10 m,the system throughput rate is up to 280 kbps,the delay is 0.42ms,and the wireless system data refresh frequency is up to 2300 Hz,which effectively complete the high-speed,high-bandwidth,and low-delay dynamic wireless measurement of the nanocapacitance sensor and realizes the wireless measurement and control for nano-positioning.