Datasheet SGP40 (Sensirion) - 3

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1 Sensor Performance Table 1
lists specifications characterizing the gas sensing performance. The SGP40 chip provides a digital raw signal (SRAW_VOC) which is sensitive to most VOC gases typically present in indoor environments and which is proportional to the logarithm of the resistance of the sensing material. This signal is intended for further processing by an algorithm providing quantitative information about the VOC based indoor air quality. For this purpose, Sensirion offers its robust VOC Algorithm, which is included in the VOC Index driver package available on github (see SGP40 product page on Sensirion’s webpage). The algorithm maps all VOC and fresh air events to a VOC Index scale (see 3.2 VOC Index Measurement). For the specifications given below, ethanol in clean air has been used as proxy gas for typical indoor air events.
Values
1
Parameter Comments Min. Typ. Max. Units
Output signals2 VOC Index, processed value from SRAW_VOC 1 – 500 VOC Index points SRAW_VOC, digital raw value 0 – 65’535 ticks3 Measurement range Ethanol in clean air 0 – 1’000 ppm Specified range Ethanol in clear air 0.3 – 30 ppm Device-to-device VOC Index4 – <±15 – VOC Index points variation or <±15 % m.v. (the larger) Repeatability VOC Index4 – <±5 – VOC Index points or <±5 % m.v. (the larger) Limit of detection5,6 Ethanol in specified range – – <0.05 ppm or <10 % of concentration setpoint (the larger) Response time Changing concentration 63 – <10 – s from 5 to 10 ppm of ethanol at sampling interval of 1 s 90 – <30 – s Switch-on behavior Time until reliably detecting VOC events7 – <60 – s Time until specifications in this table are met – <1 – h Sensitivity6 SRAW_VOC, Ethanol in specified range – −870 – ticks doubling VOC concentration 5 to 10 ppm of ethanol −710 −870 −1’030 ticks Sampling interval VOC Index – 1 – s SRAW_VOC 0.5 1 10 s
Table 1
Gas sensing specifications at 25 °C and 50 % RH in zero air (considered as clean air for indoor air quality applications) and a power supply of VDD of 3.3 V. All concentrations refer to ethanol as test gas. 1 99 % of the sensors will be within the minimum–maximum tolerance. Typical tolerance refers to the mean of the distribution for ≥100 sensors. 2 Humidity compensated when actual humidity value is provided as input to the sensor (see section 3.1 Raw Signal Measurement). 3 Signal in ticks is proportional to the logarithm of the resistance of the sensing layer. 4 Evaluated using the calibration and test sequence according to the application note SGP40 – Testing Guide. 5 Limit of detection is defined as the minimum change of concentration required to obtain a raw signal change 3 times higher than the noise at the given concentration setpoint. 6 Parameter tested over simulated lifetime of 10 years in an indoor environment. Test conditions: continuous operation in 250 ppm of Decamethylcyclopentasiloxane (D5). 7 Signal change during 60-s event of 5 to 10 ppm of ethanol is three times larger than signal drift without this event during the same duration. www.sensirion.com Version 1.1 – September 2021 3/19