Winsen GM-702B MEMS Carbon Monoxide Gas Sensor
The Winsen GM-702B is a MEMS metal-oxide semiconductor (MOS) carbon monoxide (CO) gas sensor built on a micro-fabricated hotplate. When exposed to CO, the sensor’s conductivity changes with gas concentration, enabling simple circuits to convert the resistance change into a measurable output signal.
Key highlights
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CO detection range: 5–5000 ppm
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Low power heater: ≤ 50 mW (typ.)
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Heater drive: dual-level heating (high/low)
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High sensitivity to CO, fast response & recovery
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Ceramic package, robust MEMS structure
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Suitable for residential and industrial CO leakage detection
- Description
- Manual
Description
GM-702B is a MEMS carbon monoxide gas sensor built on a silicon micro-fabrication hotplate with metal-oxide semiconductor (MOS) gas-sensitive material. In clean air the material has low conductivity; when exposed to CO, conductivity changes with gas concentration. A simple circuit converts the resistance change into an output signal suitable for CO leakage detection.
Key Features
- MEMS technology with robust structure
- High sensitivity to carbon monoxide (CO)
- Low power consumption
- Fast response and recovery
- Simple drive circuit
Typical Applications
- Residential CO leakage alarms
- Industrial CO leakage detection
- CO safety monitors and controllers
Technical Specifications
| Item | Specification |
|---|---|
| Model | GM-702B |
| Sensor type | MEMS CO gas sensor (MOS) |
| Package | Ceramic |
| Target gas | Carbon Monoxide (CO) |
| Detection range | 5–5000 ppm (CO) |
Recommended Drive / Test Conditions
| Item | Specification |
|---|---|
| Loop voltage (Vc) | ≤ 24 V DC |
| Heater voltage (Vh) – High temp | 2.5 V ± 0.1 V (AC or DC) |
| Heater voltage (Vh) – Low temp | 0.5 V ± 0.1 V (AC or DC) |
| Heating time – High temp | 60 s ± 1 s |
| Heating time – Low temp | 90 s ± 1 s |
| Load resistance (RL) | Adjustable |
| Standard circuit Vc (for typical tests) | 5.0 V ± 0.1 V (DC) |
Electrical / Sensing Characteristics (Typical)
| Item | Specification |
|---|---|
| Heater resistance (RH, room temp.) | 80 Ω ± 20 Ω |
| Heater power consumption (PH) | ≤ 50 mW |
| Sensing resistance (RS @ 150 ppm CO) | 1 kΩ to 30 kΩ |
| Sensitivity (R0 / RS @ 150 ppm CO) | ≥ 3 |
| Standard test environment | 20 °C ± 2 °C; 55% ± 5% RH |
Pin Definition (Bottom View)
| Pin | Function |
|---|---|
| 1–2 | RH1 (Heater) |
| 3–4 | RH2 (Heater) |
| 5–6 | RS1 (Sensing) |
| 7–8 | RS2 (Sensing) |
Preheating (Aging) Guidance
After long-term storage without power, sensor resistance may drift reversibly. Preheating helps the sensor reach equilibrium. Use the same voltage as the heater voltage (Vh).
| Storage Time | Suggested Aging Time |
|---|---|
| Less than 1 month | No less than 24 hours |
| 1 to 6 months | No less than 48 hours |
| More than 6 months | No less than 72 hours |
Calibration Note
Sensor accuracy can be affected by circuit differences (e.g., reference/load resistance), sensitivity variance, temperature, humidity, interfering gases, and preheating time. For absolute concentration measurement, regular calibration (one-point or multi-point) is recommended. For relative measurement, calibration may not be required.
Cautions & Handling
- Avoid exposure to organic silicon vapors (may cause permanent sensitivity loss).
- Avoid high-concentration corrosive gases (e.g., H2S, SOx, Cl2, HCl), which can corrode the structure and reduce sensitivity.
- Avoid alkali / alkali metal salts and halogen contamination (e.g., brine, fluorine).
- Avoid water splashing/immersion; sensitivity may decrease.
- Avoid icing on the sensor surface (may damage sensing material).
- Do not exceed heater power limits; excessive power can cause irreversible heater damage. Use anti-static precautions.
- Avoid long-term exposure to very high gas concentrations, high humidity, high temperature, or heavy pollution.
- Avoid continuous vibration and strong shock/impact.
Soldering Recommendations
- Reflow soldering: neutral atmosphere, 250 ± 10 °C, avoid flux vapors.
- Manual soldering: rosin flux with minimal chlorine, ≤ 350 °C, duration ≤ 5 s.
Protective Film & Packaging
- The sensor has a protective film to reduce dust/water/atmosphere/high-temperature influence; remove the film after welding.
- Standard packing is tape packaging; other packaging may be available upon request.
- RoHS compliant.
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