The impact of ambient temperature and pressure on infrared gas analyzers

Infrared gas analyzers operate based on the Lambert-Beer law. Fluctuations in ambient temperature and pressure can alter the gas absorption characteristics and the instrument's operating conditions, leading to measurement drift and errors, which are the key environmental factors affecting detection accuracy.

Impact of Ambient Temperature

Changes in ambient temperature can interfere with the instrument's measurements in several ways:

1. First, temperature alters the energy levels of gas molecules and the position and intensity of infrared absorption peaks. At the same gas concentration, changes in infrared absorption cause range drift.
2. Second, temperature fluctuations cause the instrument's gas chamber to expand and contract thermally, resulting in tiny changes in the optical path length that directly disrupt the measurement baseline.
3. Additionally, infrared light sources, filters, and detectors are all temperature-sensitive components. Temperature changes can cause deviations in the light source's emission intensity and instability in the detector's baseline, leading to significant zero-point drift and poor data repeatability.
4. Furthermore, extremely low temperatures can easily cause water-containing or easily condensable samples to liquefy, contaminating the chamber lenses and affecting the device's proper operation.

Impact of Ambient Pressure

Ambient pressure has a more direct impact on measurements. Infrared detection essentially measures the number density of gas molecules per unit volume, and the instrument is typically calibrated under standard pressure.

• When pressure increases, gas molecular density increases, enhancing infrared absorption and resulting in falsely high measurement values.
• When pressure decreases, molecular density decreases, weakening the absorption signal and leading to falsely low measurement values.
• At the same time, severe pressure fluctuations can cause turbulent airflow within the gas chamber, leading to erratic data and increased noise.
• Transient pressure changes can also exceed the correction range of conventional pressure compensation algorithms, resulting in measurement errors.

Mitigation in Industrial Applications

In industrial applications, environmental interference is effectively mitigated by maintaining constant temperature control for the gas chamber and detection components, implementing automatic temperature and pressure compensation algorithms, and using pressure and flow stabilization preprocessing devices to ensure the instrument's measurement accuracy and stability.