This post will cover some common questions Sensirion has received and answered on their gas sensors.
What is the IP protection level of the SGP?
The SGP features a dust and water protection membrane that makes it robust against water and dust in consumer device applications. However, the SGP does not have an IP level specification.
What is the humidity cross-sensitivity of the SGP sensor?
All MOX sensors including the SGP show a certain cross-sensitivity to humidity.
The SGP30 and the SGPC3 feature an on-chip humidity compensation for the air quality signals and the raw signals. To use the on-chip humidity compensation an absolute humidity value from an external humidity sensor like the SHTxx is required.
Which gases does the SGP gas sensor measure?
Metal-oxide based gas sensors are sensitive to a broad range of gases like H2, CO, VOCs (Alcohols, Aliphatic Hydrocarbons, erpenes, Aromatic Hydrocarbons, Ketones, Esters,…), NO2,…
For indoor air quality application, the SGP is optimized for the detection of VOCs and H2. MOx sensor are not sensitive to CO2.
The sensitivity to different gases can be modified by material engineering, e.g. by changing the sensing material or adding certain doping materials and by changing the operation temperature of the sensor.
How often has the SGPxx sensor to be exposed to clean air for proper operation?
The sensor has to be exposed to clean air roughly for 10min every 1-2 weeks.
The SGP features an on-chip baseline compensation algorithm that compensates long-term drifts of the sensor signal. The baseline algorithm uses the atmospheric hydrogen background in clean air (=VOC-free air) as a reference. The baseline compensation algorithm requires that the SGP is exposed to clean air in regular intervals. A short (~10 min) exposure to clean air once a week is sufficient. In most indoor applications the sensors will be exposed to clean air in regular intervals e.g. by automatic or manual ventilation. Therefore, operation of the SGP does not require any recalibration or maintenance.
What is the expected life time of the SGP?
The main limitation for the life time of traditional MOx sensor is contamination by Siloxanes. With the SGP, Sensirion has solved the Siloxane degradation problem of MOx sensors. Accelerated Siloxane degradation tests performed as part of the qualification of the SGP ensure the stability of the sensor for more than 10 years in indoor conditions. In addition, stress tests at high temperatures and humidity are performed as part of the qualification of the SGP.
To ensure the reliability of the ASIC and the package of the SGP Sensirion performs an extensive set of accelerated life-time test according to JEDEC specifications. These tests ensure sensor reliability for 10 years of operation.
What is the conversion formula from ppb to mg/m3 for TVOC?
1 mg/m3 = 218.77 ppb
1 ppb = 0.0045 mg/m3
The conversion formula assumes a molecular mass of 111.86 g/mol, 25°C and 1.013 bar. The molecular mass is the average molecular mass of the TVOC reference gas mixture.
Does the SGP require a stable and ripple free power supply?
The SGP works with an on-chip voltage regulator. The only requirement is a voltage supply in the range of 1.62V-1.9V which is able to provide sufficient current. Please refer to the datasheet for detailed specifications.
Does the SGP require a burn-in at production site?
The SGP does not require a burn-in at the production site of the customer because the sensor has been stabilized during the production process.
SGP30: However, the sensor requires an initial stabilization time of roughly 50 min when operated for the first time.
SGPC3: The initial stabilization time depends on the operation mode (low-power or ultra-low power). It can be accelerated by operation the SGPC3 for a certain time in a high-power operation mode. With a recommended high-power operation time of 3min an initial stabilization time of ~2h for low power and ~5h for ultra-low power operation mode is achieved.