Solid State Gas Sensors & Factors Affecting Life Expectancy

Solid state sensors, also referred to as metal oxide sensors are a semiconductor based chemical sensors that have relatively simple associated electronics. During operation the sensing element is heated up and when gas enters the sensor, it reacts with the oxide coating causing a decrease in resistance between the two electrodes, which is then measured.

Factors Affecting the Lifespan of Solid State Sensors

• Typically designed to operate within a range of -20 to 50°C / -4 to 122°F
• Sensitive to changes in temperature and humidity. Changes of 10°C / 18°F or 10% RH can impair sensor performance requiring a couple hours of re-stabilization. Calibration should be done after any significant changes in temperature and/or humidity. If the location of the sensor has seasonal changes in temperature or humidity a recalibration after each change will be required to meet published specification.
• Wet environments will shorten lifespan.
• Dirty and dusty environments will shorten lifespan and require more frequent calibration.
• Requires oxygen, minimum 18% vol, for proper functioning.
• Excessive vibration or impact can damage the sensor
• Sensitive to many other gases, vapours and chemicals such as silicone, paint, alcohol-based cleaners, fumes from running engines, fuel storage containers, etc.
• Continuous exposure to gas will make the sensor reading unreliable (will read higher than calibrated value).
• Must be calibrated in the environment it will be operating in.
• Flowing dry gas over a solid state sensor can result in a negative a reaction and inaccurate readings. Using a humidification chamber adds humidity and assists in recreating a "real-world" environment for the sensor.
• When storing, package securely in a sealed container. In addition to the factors listed above, most sensors will suffer general wear and tear and it may not always be easy to detect the damage caused, making regular maintenance important to help keep the sensors in good working order.

Regular maintenance includes inspecting, cleaning if necessary, bump testing and calibration.