1、 Temperature and humidity requirements

temperature

The calibration environment temperature should be controlled within the range of (20 ± 5) ℃, and some high-precision equipment requires stricter requirements (such as ± 2 ℃). Excessive temperature fluctuations can cause changes in the thermal motion of formaldehyde molecules, affecting the sensor response characteristics and leading to measurement errors.

Example: If the temperature exceeds 25 ℃, the volatilization rate of formaldehyde in the air may increase, causing the actual concentration of calibration gas to be higher than the nominal value, resulting in a lower calibration result of the equipment.

humidity

The relative humidity should be maintained between 40% and 60% RH, avoiding extreme humidity (>80% RH) or dryness (<20% RH). High humidity may cause condensation of water vapor on the sensor surface, interfering with formaldehyde adsorption; Low humidity may lead to a decrease in sensor sensitivity.

2、 Pressure requirements

The calibration environment pressure should be close to the standard atmospheric pressure (101.325kPa), with a deviation of no more than ± 5kPa. Changes in air pressure can affect the density of gas molecules, leading to discrepancies between the actual and theoretical values of the calibration gas concentration.

For example, when calibrating equipment in high-altitude areas (air pressure<90kPa), if the air pressure is not compensated, it may result in higher formaldehyde concentration measurements.

3、 Environmental cleanliness requirements

Non interfering gas

The calibration site should avoid the presence of other volatile organic compounds (such as benzene, toluene, TVOC), smoke, dust, or corrosive gases (such as SO ₂, NO ₂), which may cross react with formaldehyde sensors and cause distortion of calibration results.

Measures: Ventilation and air exchange are required before calibration. If necessary, air purification equipment should be used to ensure that the concentration of interfering gases in the environment is below 1/10 of the detection limit of the formaldehyde sensor.

No significant airflow disturbance

During the calibration process, strong airflow (such as direct blowing from fans or air conditioning vents) should be avoided. Fluctuations in airflow can cause uneven distribution of calibration gas on the sensor surface, affecting measurement stability. It is recommended to maintain an ambient airflow velocity of less than 0.5m/s.

4、 Electromagnetic interference control

The calibration environment should be kept away from strong electromagnetic sources (such as transformers, motors, and wireless transmission equipment), as electromagnetic interference may affect the transmission of equipment circuit signals and cause fluctuations in measurement data.

The equipment should be placed at least 1 meter away from the electromagnetic interference source, and electromagnetic shielding should be applied if necessary.

5、 Lighting and vibration control

illumination

Avoid direct exposure of equipment sensors to strong light, as ultraviolet radiation may accelerate the aging of sensor surface materials and affect response accuracy. The calibration environment should be natural light or soft artificial lighting.

vibration

The calibration site needs to be kept stable, with a vibration frequency of<50Hz and an amplitude of<0.1mm. Severe vibration may cause displacement of internal components of the sensor, affecting the stability of the optical path or circuit.

6、 Calibration gas matches the environment

The calibration standard gas (such as formaldehyde standard gas) should be equilibrated for at least 30 minutes under the same temperature, humidity, and pressure conditions as the calibration environment to ensure that the gas concentration is consistent with the environmental conditions and avoid calibration errors caused by differences in gas states.

summary

When calibrating formaldehyde online monitoring equipment, it is necessary to control environmental conditions from multiple dimensions such as temperature and humidity, air pressure, cleanliness, and electromagnetic environment to ensure that the calibration process is carried out in a stable and interference free environment, in order to ensure the measurement accuracy and reliability of the equipment. If the environmental conditions do not meet the requirements, adjustments or corrections should be made first, and calibration should be completed in a constant temperature and humidity laboratory if necessary.