SHT1x / SHT7x Relative Humidity & Temperature Sensor System
www.sensirion.com
v2.01 March 2003
2/9
1 Sensor Performance Specifications
Parameter
Conditions Min. Typ. Max. Units
Humidity
Resolution (2)
0.5 0.03 0.03
%RH
8
12
12
bit
Repeatability
±0.1
%RH
Accuracy (1)
Uncertainty
linearized
see figure 1
Interchangeability
Fully interchangeable
raw data
±3
%RH
Nonlinearity
linearized
<<1
%RH
Range
0
100
%RH
Response time
1/e (63%)
slowly moving air
4
s
Hysteresis
±1
%RH
Long term stability
typical
< 1
%RH/yr
Temperature
0.04 0.01 0.01
°C
0.07 0.02 0.02
°F
Resolution (2)
12
14
14
bit
±0.1
°C
Repeatability
±0.2
°F
Accuracy
see figure 1
-40
123.8
°C
Range
-40
254.9
°F
Response Time
1/e (63%)
5
30
s
Table 1
Sensor Performance Specifications
2 Interface Specifications
SHT1x
(slave)
uC
(master)
DATA
SCK
Vdd 2.4 - 5.5V
GND
Vdd
Figure 2 Typical application circuit
2.1 Power Pins
The SHTxx requires a voltage supply between 2.4 and 5.5 V.
After powerup the device needs 11ms to reach its “sleep”
state. No commands should be sent before that time.
Power supply pins (VDD, GND) may be decoupled with a
100 nF capacitor.
2.2 Serial Interface (Bidirectional 2-wire)
The serial interface of the SHTxx is optimized for sensor
readout and power consumption and is not compatible with
I2C interfaces, see FAQ for details.
2.2.1
Serial clock input (SCK)
The SCK is used to synchronize the communication between
a microcontroller and the SHTxx. Since the interface
consists of fully static logic there is no minimum SCK
frequency.
2.2.2
Serial data (DATA)
The DATA tristate pin is used to transfer data in and out of
the device. DATA changes after the falling edge and is
valid on the rising edge of the serial clock SCK. During
transmission the DATA line must remain stable while SCK is
high. To avoid signal contention the microcontroller should
only drive DATA low. An external pull-up resistor (e.g. 10 kΩ )
is required to pull the signal high. (See Figure 2) Pull-up
resistors are often included in I/O circuits of microcontrollers.
See Table 5 for detailed IO characteristics.
(1)
Each SHTxx is tested to be fully within RH accuracy specifications at 25 °C (77 °F) and 48 °C (118.4 °F)
(2)
The default measurement resolution of 14bit (temperature) and 12bit (humidity) can be reduced to 12 and 8 bit through the status register.
%RH
Relative Humidity absolute accuracy
± 0
± 1
± 2
± 3
± 4
± 5
0
30 40
20
10
80
50
100
70
90
60
Temperature accuracy
0 °C
±1 °C
±2 °C
-40°C
0°C
40°C
80°C
120°C
±3 °C
Dewpoint accuracy @ 25 °C (typical)
±0 °C
±1 °C
±2 °C
±3 °C
±4 °C
±5 °C
0
30 40
20
10
80
50
100
70
90
60
0 °F
±1.8 °F
±3.6 °F
±5.4 °F
%RH
±1.8 °F
±3.6 °F
±7.2 °F
±5.4 °F
±9.0 °F
-40°F32°F104°F176°F248°F
%RH
SHT11/71
SHT15/75
SHT11/71
SHT15/75
SHT11/71
SHT15/75
Figure 1 Rel. Humidity, Temperature and Dewpoint accuracies
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