Datasheet

www.sensirion.com
Version 1.0 – July 2020 – D1
3/19
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
VOC Index driver package available on Sensirion’s webpage.
1
The algorithm maps all VOC and fresh air events to a VOC Index
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
Values
2
Units
Min.
Typ.
Max.
Output signals
3
Digital processed value (VOC Index)
0
–
500
VOC Index points
Digital raw value (SRAW)
0
–
65’535
ticks
4
Measurement range
Ethanol in clean air
0
–
1’000
ppm
Specified range
Ethanol in clear air
0.3
–
30
ppm
Device-to-device
variation
VOC Index
5
–
<±15
<±15
–
VOC Index points
or
% VOC Index m.v.
(the larger)
Repeatability
VOC Index
5
–
<±5
<±5
–
VOC Index points
or
% VOC Index m.v.
(the larger)
Limit of detection
6,7
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

63
–
<10
–
s

90
–
<30
–
s
Switch-on behavior
Time until reliably detecting VOC events
8
–
<60
–
s
Time until specifications in this table are
met
–
<1
–
h
Sensitivity
7
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
supply of V
DD
of 3.3 V. All concentrations refer to ethanol as test gas.
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.