Gas sensor

Introduction

The semiconductor gas sensor for carbon monoxide/combustible gas detection uses a gas-sensitive material, tin dioxide (SnO2), which has a low conductivity in clean air. The high and low-temperature cycle detection method is used to detect carbon monoxide at low temperature (1.5V heating), where the conductivity of the sensor increases with the concentration of carbon monoxide gas in the air, and to detect the combustible gases methane and propane at high temperature (5.0V heating), and to clean up the stray gases that are adsorbed at low temperature. A simple circuit is used to convert the change in conductivity to an output signal corresponding to the concentration of the gas.

Team Members

Fu Xinming, Ge Yexiao, Yang Haoqing

Setup

The diagram above shows the basic test circuit for the sensor. The sensor requires two voltages to be applied: the heater voltage (VH) and the test voltage (VC). VH is used to provide the sensor with a specific operating temperature and VC is used to determine the voltage (VRL) across the load resistor (RL) connected in series with the sensor. VC is used to determine the voltage (VRL) across the load resistor (RL) in series with the sensor. The sensor has a slight VC requires a DC power supply. VC and VH can be used as long as the electrical requirements of the sensor are met. VC and VH can share the same power supply circuit if the electrical requirements of the sensor are met. To take advantage of the sensor's performance of the sensor, it is necessary to select the appropriate RL value.

Equipment

Gas Sensitive Components

One-chip computer/microcontroller

ADC conversion module

Timeline and Milestone

Timeline

Week 8 (3/4 — 3/8)	Debug sensor module hardware devices and software code
Week 9 — Week 10（3/11 — 3/22)	Measurements using gas sensors to obtain a database
Week 11 — Week 12（3/25 — 4/5）	Fit curve to obtain the corresponding relationship between the output value and the gas concentration
Week 13 (4/8 — 4/12)	Analyze experimental results and complete reports

Expected Results

We hope to obtain a curve between the output value and the corresponding gas concentration, so as to know the pollution situation in the environment relatively accurately.