Datasheet

www.sensirion.com Version 4 – May 2014 3/14
Users Guide SHT21
1 Extended Specification
For details on how Sensirion is specifying and testing
accuracy performance please consult Application Note
“Statement on Sensor Specification”.
1.1 Operating Range
The sensor works stable within recommended Normal
Range – see Figure 4. Long term exposure to conditions
outside Normal Range, especially at humidity >80%RH,
may temporarily offset the RH signal (+3%RH after 60h).
After return into the Normal Range it will slowly return
towards calibration state by itself. Prolonged exposure to
extreme conditions may accelerate ageing.
Figure 4 Operating Conditions
1.2 RH accuracy at various temperatures
Typical RH accuracy at 25°C is defined in Figure 2. For
other temperatures, typical accuracy has been evaluated
to be as displayed in Figure 5.
100 ±3.5 ±3 ±3 ±3 ±3 ±3 ±3.5 ±4 ±4
90 ±3.5 ±3 ±2.5 ±2.5 ±2.5 ±2.5 ±3 ±3.5 ±4
80 ±3 ±2.5 ±2 ±2 ±2 ±2.5 ±2.5 ±3 ±3.5
70 ±3 ±2.5 ±2 ±2 ±2 ±2 ±2.5 ±2.5 ±3
60 ±2.5 ±2 ±2 ±2 ±2 ±2 ±2 ±2.5 ±2.5
50 ±2.5 ±2 ±2 ±2 ±2 ±2 ±2 ±2 ±2.5
40 ±2.5 ±2 ±2 ±2 ±2 ±2 ±2 ±2 ±2
30 ±2.5 ±2 ±2 ±2 ±2 ±2 ±2 ±2 ±2
20 ±2.5 ±2.5 ±2 ±2 ±2 ±2 ±2 ±2 ±2
10 ±3 ±3 ±2.5 ±2.5 ±2.5 ±2.5 ±2.5 ±2.5 ±2.5
0 ±3.5 ±3.5 ±3 ±3 ±3 ±3 ±3 ±3 ±3
0 10 20 30 40 50 60 70 80
Relative Humidity [%RH]
Temperature [°C]
Figure 5 Typical accuracy of relative humidity measurements
given in %RH for temperatures 0 – 80°C.
1.3 Electrical Specification
Current consumption as given in Table 1 is dependent on
temperature and supply voltage VDD. For estimations on
energy consumption of the sensor Figures 6 and 7 may be
consulted. Please note that values given in these Figures
are of typical nature and the variance is considerable.
0
1
2
3
4
5
6
7
8
0 20 40 60 80 100 120
Temperature (°C)
Supply Current IDD (μA)
Figure 6 Typical dependency of supply current (sleep mode)
versus temperature at VDD = 3.0V. Please note that the
variance of these data can be above ±25% of displayed value.
6
8
10
12
14
16
18
20
2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5
Supply Voltage (VDD)
Supply Current IDD (nA)
Figure 7 Typical dependency of supply current (sleep mode)
versus supply voltage at 25°C. Please note that deviations may
be up to ±50% of displayed value. Values at 60°C scale with a
factor of about 15 (compare Table 1).
0
20
40
60
80
100
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Relative Humidity (%)
Max.
Range
Normal
Range