MEMS VOC Gas Sensor

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Thanks for purchasing our product. In order to let the customer use it better and reduce the faults caused by misuse, please read the manual carefully and operate it correctly in accordance with the instructions. If users disobey the terms or remove, disassemble, change the components inside of the sensor, Zhengzhou Winsen Electronics Technology Co., LTD shall not be responsible for the loss.

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GM-502B MEMS VOC Gas Sensor

Product description

MEMS VOC gas sensor is using MEMS micro-fabrication hot plate on a Si substrate base, gas-sensitive materials used in the clean air with low conductivity metal oxide semiconductor material. When the sensor is exposed to gas atmosphere, the conductivity is changing as the detected gas concentration in the air. The higher the concentration of the gas, the higher the conductivity. A simple circuit can convert the change of conductivity of the gas concentration corresponding to the output signal.

Characters:

• MEMS technology, strong structure
• Low power consumption
• High sensitivity
• Fast response and resume
• Simple drive circuit

Application

Gas leak detection for mobile phones, computers and other consumer electronics applications, also for breathing gas detection control, smoke alarm indoor etc.

Main Parameter:

Sensor Structure Diagram

The diagram shows a rectangular sensor with multiple circular contact points on top and a grid-like pattern on the bottom. Dimensions are provided in millimeters: top view shows 1.17 x 0.64, side view shows 1.55 and 2.08, bottom view shows a 5x5 grid with contact pads.

Pin Configuration:

Recommend Circuit

The recommended circuit diagram shows the gas sensor connected to a power source (+2.5V for Heating1 and Heating2) and a measurement circuit. Measure1 and Measure2 are connected to the sensor's pins, with Vout outputting the signal. The circuit utilizes a load resistor (RL) in series with the sensor. Instructions indicate that the sensor requires two voltage inputs: heater voltage (VH) and circuit voltage (Vc). VH supplies the working temperature and can be AC or DC. Vc supplies the detection voltage to the load resistor (RL) and should be DC.

Sensitivity Characteristics

Fig3. Typical Sensitivity Curve: This graph illustrates the sensor's response (Rs/Ro) to different gas concentrations (ppm). Rs represents resistance in the target gas, and Ro represents resistance in clean air. All tests are conducted under standard test conditions.

Fig4. Typical temperature/humidity characteristics: This graph shows how the sensor's resistance (Rs) in 50ppm alcohol gas changes with temperature and humidity. Rso is the resistance under standard conditions (20°C/55%RH).

Fig5. Response and Resume: This graph displays the output voltage (of RL in series with the sensor) over time when exposed to 50ppm alcohol gas. It demonstrates the sensor's response time and recovery time.

Fig6. Linearity character: This graph shows the output voltage (of RL in series with the sensor) versus gas concentration (ppm) for different gases (alcohol, acetone, benzene, formaldehyde). Tests are performed under standard conditions.

Long-term stability

Fig7. Long-term Stability: This graph plots the output voltage (Vo and Vs50ppm) over time (days) in clean air and in 50ppm alcohol, respectively. It indicates the sensor's stability over an extended period.

Instructions:

1. Preheating time: Sensor resistance may drift after long-term storage without power. Preheat the sensor to reach chemical equilibrium using heating voltage VH. Suggested preheating times based on storage duration:
   • Less than one month: No less than 24 hours
   • 1~6 months: No less than 48 hours
   • More than six months: No less than 72 hours
2. Calibration: Sensor accuracy is affected by various factors including reference resistance, sensitivity, temperature, humidity, interfering gases, preheating time, and linearity. For absolute concentration measurement, regular calibration (one-point or multi-points) is necessary. For relative measurement, calibration is not required.

Cautions:

1. Following conditions must be prohibited:
   • 1.1 Exposed to organic silicon steam: Sensing material loses sensitivity and cannot recover if exposed to organic silicon steam. Avoid contact with silicon bond, fixature, silicon latex, putty, or plastics containing silicon.
   • 1.2 High Corrosive gas: Exposure to high concentrations of corrosive gases (e.g., H2S, SOX, Cl2, HCL) can corrode the sensor structure and cause significant sensitivity attenuation.
   • 1.3 Alkali, Alkali metals salt, halogen pollution: Sensor performance can be severely affected by exposure to alkali metals salts, brine, or halogens like fluorine.
   • 1.4 Touch water: Sensitivity will be reduced if spattered or dipped in water.
   • 1.5 Freezing: Avoid icing on the sensor surface, as it can break the sensing material and cause loss of sensitivity.
   • 1.6 Applied voltage: Applied voltage should not exceed 120mW, as it can cause irreversible heater damage. Take anti-static precautions when handling sensors.
2. Following conditions must be avoided:
   • 2.1 Water Condensation: Slight condensation can lightly influence sensor performance. Prolonged condensation on the sensor surface will decrease sensitivity.
   • 2.2 Used in high gas concentration: Prolonged exposure to high gas concentrations, whether electrified or not, affects sensor characteristics. Lighter gas sprays can cause extreme damage.
   • 2.3 Long time exposed to extreme environment: Exposure to adverse environments (high humidity, high temperature, high pollution) for extended periods will negatively impact sensor performance.
   • 2.4 Vibration: Continuous vibration can cause sensor down-lead response and breakage. Pneumatic screwdrivers or ultrasonic welding machines can cause this during transportation or assembly.
   • 2.5 Concussion: Strong concussion may lead to disconnected lead wires.
   • 2.6 Soldering:
     • 2.6.1 Recommended conditions for reflow soldering: Neutral atmosphere, soldering temperature 250±10℃, avoid flux steam.
     • 2.6.2 Recommended conditions for manually soldering: Rosin flux with least chlorine, soldering temperature ≤350 ℃, lasting time ≤5s.

Disobeying these terms will reduce sensor sensitivity.

Package

The MEMS sensor surface is protected by a special film to prevent dust, water, atmosphere, and high temperature influence. This protective film can be removed after welding is completed.

The diagram shows the packaging of the sensor on a reel, with dimensions provided. It also shows individual sensors in protective packaging.

Zhengzhou Winsen Electronics Technology Co., Ltd

Add: No.299, Jinsuo Road, National Hi-Tech Zone, Zhengzhou 450001 China

Tel: +86-371-67169097/67169670

Fax: +86-371-60932988

E-mail: sales@winsensor.com

Website: www.winsen-sensor.com