Design Of Signal Acquisition Circuit For Nanoscale Material Gas Sensor

With social development,gas sensors are broadly applied in various fields,such as home security systems,food safety testing,medical equipment and environmental control,all of which are inalienable from gas sensors.Compared with common gas sensors,the gas sensors prepared by the new nanomaterials have high sensitivity and excellent gas selectivity,and are suitable for detecting tiny changes in the gas environment.Such gas sensors need to measure the changing resistance signal during the test,and the features of the nanomaterial causes the sensor to have a wide range of output resistance,so the sensor need the signal acquisition system to precisely and continuously detect the sensor.The change in resistance.The main contents of this paper are as follows:(1)According to the characteristics of nanomaterial gas sensor,with STM32 microcontroller,a wide dynamic range signal acquisition circuit system is designed,which can realize the simultaneous measurement of 8-channel signals,and its single measurement time is less than 30 ms.Measurement accuracy of 5 % of maximum linearity error over the full range of 1 KΩ-100 MΩ;(2)Study the two kinds of resistance measuring circuit such as proportional amplification circuit and current integration circuit.Compare the software filtering algorithm used in the signal acquisition circuit system,and the proper software and hardware is selected according to the actual analysis;(3)Verify and analyze the circuit through virtual test and actual sensor test.According to the test results,the selection of critical devices in the circuit was studied and discussed.Compared with traditional resistance measurement instrument,the signal acquisition system designed in this thesis is much better in circuit and data processing:(1)A specific signal acquisition system for nanomaterial gas sensors which has wide measurement range and strong anti-interference ability can realize a long-term testing of multiple gas sensors,and is universal with variety gas sensing instruments;(2)The signal acquisition circuit combines the advantages of the proportional amplification circuit on the small resistance measurement and the current integration circuit which has extremely wide resistance measurement range.The circuit has the characteristics of small size and low power consumption which make the circuit suitable for many different types of gas sensors;(3)The signal acquired by the circuit is processed by software filtering.The raw data is processed by the algorithm of sliding weighted average filtering;for the proportional amplifying circuit,the range hysteresis switching algorithm is used to improve the accuracy and stability of the measuring circuit.The resistive gas sensor measurement circuit designed in this paper can be applied to the gas sensor test system,which makes a stable basic for the research and application of the innovative nanomaterial gas sensor.