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Version 1.0 – July 2020 – D1

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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)

which is sensitive to all VOC gases typically present in indoor environments and which is proportional to the logarithm of the

resistance of the MOx 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

scale (see application note SGP40 – VOC Index for Experts for more details). For the specifications given below, ethanol in

clean air has been used as proxy gas for typical indoor air events.

Parameter

Comments

Units

Min.

Typ.

Max.

Digital processed value (VOC Index)

0

–

500

VOC Index points

Digital raw value (SRAW)

0

–

65’535

Measurement range Ethanol in clean air

0

–

1’000

ppm

Specified range

Ethanol in clear air

0.3

–

30

ppm

Device-to-device

variation

–

<±15

<±15

–

VOC Index points

or

% VOC Index m.v.

(the larger)

Repeatability

VOC Index5

–

<±5

<±5

–

VOC Index points

or

% VOC Index m.v.

(the larger)

Ethanol in specified range

–

–

<50

<10

ppb

or

% of concentration setpoint

(the larger)

Response time

Changing concentration

from 5 to 10 ppm of ethanol, at

sampling interval of 1 s

–

<10

–

s

–

<30

–

s

Switch-on behavior

–

<60

–

s

Time until specifications in this table are

met

–

<1

–

h

Sensitivity7

SRAW,

doubling VOC

concentration

Ethanol in specified

range

–

−870

–

ticks

5 to 10 ppm of

ethanol

−710

−870

−1’030

ticks

Recommended

sampling interval

VOC Index

–

1

–

s

SRAW

10

1

0.5

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

1

Download the VOC Index Driver Package SGP40 on https://www.sensirion.com/en/download-center/gas-sensors/multi-pixel-gas-sensors/.

2

99.99 % of the sensors will be within the minimum–maximum tolerance corresponding to 4σ assuming a normal distribution. Typical tolerance refers to the mean of the

distribution for ≥100 sensors.

3

Humidity compensated when actual humidity value is provided as input to the sensor (see section 3.1 Raw Signal Measurement).

4

Signal in ticks is proportional to the logarithm of the resistance of the sensing layer.

5

Evaluated using the calibration and test sequence according to the application note SGP40 – Testing Guide.

6

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.

7

Parameter tested over simulated lifetime of 10 years in an indoor environment. Test conditions: continuous operation in 250 ppm of Decamethylcyclopentasiloxane (D5).

8

Signal increase 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.