SHT1x / SHT7x Relative Humidity & Temperature Sensor System

www.sensirion.com

v2.02 July 2004

2/9

1 Sensor Performance Specifications

Parameter

Conditions Min. Typ. Max. Units

Humidity

0.5 0.03 0.03

%RH

8

12

12

bit

Repeatability

±0.1

%RH

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

< 0.5

%RH/yr

Temperature

0.04 0.01 0.01

°C

0.07 0.02 0.02

°F

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

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

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°F

32°F

104°F

176°F

248°F

%RH

SHT75

SHT75

SHT11/71

SHT15

SHT11/71

SHT15

SHT11/71

SHT15/75

Figure 1 Rel. Humidity, Temperature and Dewpoint accuracies