www.sensirion.com
Version 5 – December 2011 1/12
Datasheet SHT7x (SHT71, SHT75)
Humidity and Temperature Sensor IC
Fully calibrated
Digital output
Low power consumption
Excellent long term stability
Pin type package – easy integration
Dimensions
Figure 1: Drawing of SHT7x (applies to SHT71 and SHT75)
sensor packaging, dimensions in mm (1mm = 0.039inch).
Contact assignment: 1: SCK, 2: VDD, 3: GND, 4: DATA.
Hatched item on backside of PCB is a 100nF capacitor – see
Section 2.1 for more information.
Sensor Chip
SHT7x V4 – for which this datasheet applies – features a
version 4 Silicon sensor chip. Besides a humidity and a
temperature sensor the chip contains an amplifier, A/D
converter, OTP memory and a digital interface. V4 sensors
can be identified by the alpha-numeric traceability code on
the sensor cap – see example “B2G” code on Figure 1.
Material Contents
While the sensor is made of a CMOS chip the sensor
housing consists of an LCP cap with epoxy glob top on an
FR4 substrate. Pins are made of a Cu/Be alloy coated with
Ni and Au. The device is fully RoHS and WEEE compliant,
thus it is free of Pb, Cd, Hg, Cr(6+), PBB and PBDE.
Evaluation Kits
For sensor trial measurements, for qualification of the
sensor or even experimental application (data logging) of
the sensor there is an evaluation kit EK-H4 available
including SHT71 (same sensor chip as SHT1x) and 4
sensor channels, hard and software to interface with a
computer. For other evaluation kits please check
www.sensirion.com/humidity.
Ø 0.4
3.1
2.2
0.6
2.0
0.2
3.7
19.5
6.0
3.4
3.7
13.5
6.4
1.2
0.46
1.27
5.08
71
B2G
1
2
3
4
Product Summary
SHT7x (including SHT71 and SHT75) is Sensirion’s family
of relative humidity and temperature sensors with pins.
The sensors integrate sensor elements plus signal
processing in compact format and provide a fully
calibrated digital output. A unique capacitive sensor
element is used for measuring relative humidity while
temperature is measured by a band-gap sensor. The
applied CMOSens® technology guarantees excellent
reliability and long term stability. Both sensors are
seamlessly coupled to a 14bit analog to digital converter
and a serial interface circuit. This results in superior signal
quality, a fast response time and insensitivity to external
disturbances (EMC).
Each SHT7x is individually calibrated in a precision
humidity chamber. The calibration coefficients are
programmed into an OTP memory on the chip. These
coefficients are used to internally calibrate the signals
from the sensors.
The 2-
wire serial interface and internal
voltage regulation allows for easy and
fast system
integration. The small size and low power consumption
makes SHT7x the ultimate choice for even the most
demanding applications.
SHT7x is supplied on FR4 with pins which allows for easy
integration or replacement. The same sensor is also
available as
surface mountable packaging (SHT1x) or on
flex print (SHTA1).
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 2/12
Sensor Performance
Relative Humidity
12
Parameter
Condition
min
typ
max
Units
Resolution
1
0.4
0.05
0.05
%RH
8
12
12
bit
Accuracy
2
SHT71
typ ±3.0 %RH
max
see Figure 2
Accuracy
2
SHT75
typ ±1.8 %RH
max
see Figure 2
Repeatability ±0.1 %RH
Hysteresis ±1 %RH
Nonlinearity raw data ±3 %RH
linearized
<<
1
%RH
Response time
3
tau 63%
8
s
Operating Range
0
100
%RH
Long term drift
4
normal
< 0.5
%RH/yr
Figure 2: Maximal RH-tolerance at 25°C per sensor type.
Electrical and General Items
Parameter
Condition
min
typ
max
Units
Source Voltage
2.4
3.3
5.5
V
Power
Consumption
5
sleep
2
5
µW
measuring
3
mW
average
90
µW
Communication
digital 2
-
wire interface, see Communication
Storage
10
–
50°C (0
–
80°C peak), 20
–
60%RH
1
The default measurement resolution of is 14bit for temperature and 12bit for
humidity. It can be reduced to 12/8bit by command to status register.
2
Accuracies are tested at Outgoing Quality Control at 25°C (77°F) and 3.3V.
Values exclude hysteresis and are only applicable to non-condensing
environments.
3
Time for reaching 63% of a step function, valid at 25°C and 1 m/s airflow.
Temperature
45
Parameter
Condition
min
typ
max
Units
Resolution
1
0.04
0.01
0.01
°
C
12
14
14
bit
Accuracy
2
SHT71
typ ±0.4 °C
max
see Figure 3
Accuracy
2
SHT75
typ ±0.3 °C
max see Figure 3
Repeatability ±0.1 °C
Operating Range
-
40
123.8
°
C
-
40
254.9
°F
Response Time
6
tau 63%
5
30
s
Long term drift
< 0.04
°C/yr
Figure 3: Maximal T-tolerance per sensor type.
Packaging Information
Sensor Type
Packaging
Quantity
Order Number
SHT71
Tape
Stripes
50
1
-
100092
-
04
SHT75
Tape Stripes
50
1
-
100071
-
04
This datasheet is subject to change and may be
amended without prior notice.
4
Value may be higher in environments with high contents of volatile organic
compounds. See Section 1.3 of Users Guide.
5
Values for VDD=3.3V at 25°C, average value at one 12bit measurement
per second.
6
Response time depends on heat capacity of and thermal resistance to
sensor substrate.
SHT71
SHT75
± 0
± 2
± 4
± 6
0 10 20 30 40 50 60 70 80 90 100
DRH (%RH)
Relative Humidity (%RH)
SHT71
SHT75
± 0.0
± 0.5
± 1.0
± 1.5
± 2.0
± 2.5
± 3.0
-40 -20 0 20 40 60 80 100
DT (°
°
°
°C)
Temperature (°C)
www.sensirion.com
Version 5 – December 2011 3/12
Users Guide SHT7x
1 Application Information
1.1 Operating Conditions
Sensor works stable within recommended normal range –
see Figure 4. Long term exposures to conditions outside
normal range, especially at humidity >80%RH, may
temporarily offset the RH signal (+3 %RH after 60h). After
return to normal range it will slowly return towards
calibration state by itself. See Section 1.4 “Reconditioning
Procedure” to accelerate eliminating the offset. Prolonged
exposure to extreme conditions may accelerate ageing.
Figure 4: Operating Conditions
1.2 Sockets and Soldering
For maintain high accuracy specifications the sensor shall
not be soldered. Sockets may be used such as “Preci-dip /
Mill-Max R851-83-004-20-001” or similar.
Standard wave soldering ovens may be used at maximum
235°C for 20 seconds. For manual soldering contact time
must be limited to 5 seconds at up to 350°C
7
.
After wave soldering the devices should be stored at
>75%RH for at least 12h to allow the polymer to re-
hydrate.
Alternatively the re-hydration process may be
performed at ambient conditions (>40%RH) during more
than 5 days.
In no case, neither after manual nor wave soldering, a
board wash shall be applied. In case of application with
exposure of the sensor to corrosive gases the soldering
pads of pins and PCB shall be sealed to prevent loose
contacts or short cuts.
1.3 Storage Conditions and Handling Instructions
It is of great importance to understand that a humidity
sensor is not a normal electronic component and needs to
be handled with care. Chemical vapors at high
concentration in combination with long exposure times
may offset the sensor reading.
7
235°C corresponds to 455°F, 350°C corresponds to 662°F
For these reasons it is recommended to store the sensors
in original packaging including the sealed ESD bag at
following conditions: Temperature shall be in the range of
10°C – 50°C (0 – 80°C for limited time) and humidity at 20
– 60%RH (sensors that are not stored in ESD bags). For
sensors that have been removed from the original
packaging we recommend to store them in ESD bags
made of metal-in PE-HD
8
.
In manufacturing and transport the sensors shall be
prevented of high concentration of chemical solvents and
long exposure times. Out-gassing of glues, adhesive tapes
and stickers or out-gassing packaging material such as
bubble foils, foams, etc. shall be avoided. Manufacturing
area shall be well ventilated.
For more detailed information please consult the
document “Handling Instructions” or contact Sensirion.
1.4 Reconditioning Procedure
As stated above extreme conditions or exposure to solvent
vapors may offset the sensor. The following reconditioning
procedure may bring the sensor back to calibration state:
Baking: 100 – 105°C at < 5%RH for 10h
Re-Hydration: 20 – 30°C at ~ 75%RH for 12h
9
.
1.5 Temperature Effects
Relative humidity reading strongly depends on
temperature. Therefore, it is essential to keep humidity
sensors at the same temperature as the air of which the
relative humidity is to be measured. In case of testing or
qualification the reference sensor and test sensor must
show equal temperature to allow for comparing humidity
readings.
The packaging of SHT7x is designed for minimal heat
transfer from the pins to the sensor. Still, if the SHT7x
shares a PCB with electronic components that produce
heat it should be mounted in a way that prevents heat
transfer or keeps it as low as possible.
Furthermore, there are self-heating effects in case the
measurement frequency is too high. Please refer to
Section 3.3 for detailed information.
8
For example, 3M antistatic bag, product “1910” with zipper .
9
75%RH can conveniently be generated with saturated NaCl solution.
100 – 105°C correspond to 212 – 221°F, 20 – 30°C correspond to 68 – 86°F
Max. Range
Normal
Range
0
20
40
60
80
100
-40 -20 0 20 40 60 80 100 120
Relative Humidity (%)
Temperature (°C)
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 4/12
1.6 Light
The SHT7x is not light sensitive. Prolonged direct
exposure to sunshine or strong UV radiation may age the
housing.
1.7 Materials Used for Sealing / Mounting
Many materials absorb humidity and will act as a buffer
increasing response times and hysteresis. Materials in the
vicinity of the sensor must therefore be carefully chosen.
Recommended materials are: Any metals, LCP, POM
(Delrin), PTFE (Teflon), PE, PEEK, PP, PB, PPS, PSU,
PVDF, PVF.
For sealing and gluing (use sparingly): Use high filled
epoxy for electronic packaging (e.g. glob top, underfill),
and Silicone. Out-gassing of these materials may also
contaminate the SHT7x (see Section 1.3). Therefore try to
add the sensor as a last manufacturing step to the
assembly, store the assembly well ventilated after
manufacturing or bake at 50°C for 24h to outgas
contaminants before packing.
1.8 Wiring Considerations and Signal Integrity
SHT7x are often applied using wires. Carrying the SCK
and DATA signal parallel and in close proximity more than
10cm may result in cross talk and loss of communication.
This may be resolved by routing VDD and/or GND
between the two data signals and/or using shielded
cables. Furthermore, slowing down SCK frequency will
possibly improve signal integrity.
Please see the Application Note “ESD, Latch-up and
EMC” for more information.
1.9 ESD (Electrostatic Discharge)
ESD immunity is qualified according to MIL STD 883E,
method 3015 (Human Body Model at ±2 kV).
Latch-up immunity is provided at a force current of
±100mA with T
amb
= 80°C according to JEDEC78A. See
Application Note “ESD, Latch-up and EMC” for more
information.
2 Interface Specifications
Pin
Name
Comment
1
SCK
Serial Clock, input only
2
VDD
Source Voltage
3
GND
Ground
4
DATA
Serial Data, bidirectional
Table 1: SHT7x pin assignment.
2.1 Power Pins (VDD, GND)
The supply voltage of SHT7x must be in the range of 2.4
and 5.5V, recommended supply voltage is 3.3V.
Decoupling of VDD and GND by a 100nF capacitor is
integrated on the backside of the sensor packaging.
The serial interface of the SHT7x is optimized for sensor
readout and effective power consumption. The sensor
cannot be addressed by I
2
C protocol, however, the sensor
can be connected to an I
2
C bus without interference with
other devices connected to the bus. Microcontroller must
switch between protocols.
Figure 5: Typical application circuit, including pull up resistor R
P
.
2.2 Serial clock input (SCK)
SCK is used to synchronize the communication between
microcontroller and SHT7x. Since the interface consists of
fully static logic there is no minimum SCK frequency.
2.3 Serial data (DATA)
The DATA tri-state pin is used to transfer data in and out
of the sensor. For sending a command to the sensor,
DATA is valid on the rising edge of the serial clock (SCK)
and must remain stable while SCK is high. After the falling
edge of SCK the DATA value may be changed. For safe
communication DATA valid shall be extended T
SU
and T
HO
before the rising and after the falling edge of SCK,
respectively – see Figure 6. For reading data from the
sensor, DATA is valid T
V
after SCK has gone low and
remains valid until the next falling edge of SCK.
To avoid signal contention the microcontroller must only
drive DATA low. An external pull-up resistor (e.g. 10 kΩ) is
required to pull the signal high – it should be noted that
pull-up resistors may be included in I/O circuits of
VDD
GND
DATA
SCK
71
B2G
1
2
3
4
Micro-
Controller
(Master)
SHT7x
(Slave)
R
P
10kΩ
B2G
71
1
2
3
4
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 5/12
microcontrollers. See Table 2 for detailed I/O characteristic
of the sensor.
2.4 Electrical Characteristics
The electrical characteristics such as power consumption,
low and high level, input and output voltages depend on
the supply voltage. Table 2 gives electrical characteristics
of SHT7x with the assumption of 5V supply voltage if not
stated otherwise. For proper communication with the
sensor it is essential to make sure that signal design is
strictly within the limits given in Table 3 and Figure 6.
Absolute maximum ratings for VDD versus GND are +7V
and -0.3V.
Exposure to absolute maximum rating
conditions for extended periods may affect the sensor
reliability (e.g. hot carrier degradation, oxide breakdown).
Parameter
Conditions
min
typ
max
Units
Power supply DC
10
2.4
3.3
5.5
V
Supply current
measuring
0.55
1
mA
average
11
2
28
µA
sleep
0.3
1.5
µA
Low level output
voltage I
OL
< 4 mA 0 250 mV
High level output
voltage R
P
< 25 kΩ 90% 100%
VDD
Low level input
voltage Negative going
0% 20% VDD
High level input
voltage Positive going 80% 100%
VDD
Input current on
pads 1 µA
Output current
on
4
mA
Tri
-
stated (off)
10
20
µA
Table 2: SHT7x DC characteristics. R
P
stands for pull up
resistor, while I
OL
is low level output current.
Figure 6: Timing Diagram, abbreviations are explained in
Table 3. Bold DATA line is controlled by the sensor, plain DATA
line is controlled by the micro-controller. Note that DATA valid
read time is triggered by falling edge of anterior toggle.
10
Recommended voltage supply for highest accuracy is 3.3V, due to sensor
calibration.
11
Minimum value with one measurement of 8 bit resolution without OTP reload
per second, typical value with one measurement of 12bit resolution per
second.
Parameter Conditions min typ max
Units
F
SCK
SCK Frequency VDD > 4.5V
0 0.1 5 MHz
VDD < 4.5V
0 0.1 1 MHz
T
SCKx
SCK hi/low time 100
ns
T
R
/T
F
SCK rise/fall time 1 200
* ns
T
FO
DATA fall time OL = 5pF 3.5 10 20 ns
OL = 100pF
30 40 200
ns
T
RO
DATA rise time ** ** ** ns
T
V
DATA valid time 200
250
*** ns
T
SU
DATA setup time 100
150
*** ns
T
HO
DATA hold time 10 15 **** ns
*
T
R_max
+ T
F_max
= (F
SCK
)
-1
–
T
SCKH
–
T
SCKL
**
T
R0
is
determined by the R
P
*C
bus
time
-
constant at DATA line
***
T
V_max
and T
SU_max
depend on external pull
-
up resistor (R
P
) and total bus
line capacitance (Cbus) at DATA line
****
T
H0_max
< T
V
–
max (T
R0
, T
F0
)
Table 3: SHT7x I/O signal characteristics, OL stands for Output
Load, entities are displayed in Figure 6.
3 Communication with Sensor
3.1 Start up Sensor
As a first step the sensor is powered up to chosen supply
voltage VDD. The slew rate during power up shall not fall
below 1V/ms. After power-up the sensor needs 11ms to
get to Sleep State. No commands must be sent before
that time.
3.2 Sending a Command
To initiate a transmission, a Transmission Start sequence
has to be issued. It consists of a lowering of the DATA line
while SCK is high, followed by a low pulse on SCK and
raising DATA again while SCK is still high – see Figure 7.
Figure 7: "Transmission Start" sequence
The subsequent command consists of three address bits
(only ‘000’ is supported) and five command bits. The
SHT7x indicates the proper reception of a command by
pulling the DATA pin low (ACK bit) after the falling edge of
the 8th SCK clock. The DATA line is released (and goes
high) after the falling edge of the 9th SCK clock.
DATA
SCK
80%
2
0%
80%
2
0%
DATA valid read
DATA valid write
DATA
SCK
80%
2
0%
80%
2
0%
T
V
T
SCKL
T
SU
T
HO
T
SCK
T
SCKH
T
R
T
F
T
RO
T
FO
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 6/12
Command
Code
Reserved
0000x
Measure
Temperature
00011
Measure Relative Humidity
00101
Read Status Register
00111
Write Status Register
00110
Reserved
0101x
-
1110x
Soft reset,
resets the interface, clears the
status register to default values. Wait minimum
11 ms before next command
11110
Table 4: SHT7x list of commands
3.3 Measurement of RH and T
After issuing a measurement command (‘00000101’ for
relative humidity, ‘00000011’ for temperature) the
controller has to wait for the measurement to complete.
This takes a maximum of 20/80/320 ms for a 8/12/14bit
measurement. The time varies with the speed of the
internal oscillator and can be lower by up to 30%. To
signal the completion of a measurement, the SHT7x pulls
data line low and enters Idle Mode. The controller must
wait for this Data Ready signal before restarting SCK to
readout the data. Measurement data is stored until
readout, therefore the controller can continue with other
tasks and readout at its convenience.
Two bytes of measurement data and one byte of CRC
checksum (optional) will then be transmitted. The micro
controller must acknowledge each byte by pulling the
DATA line low. All values are MSB first, right justified (e.g.
the 5
th
SCK is MSB for a 12bit value, for a 8bit result the
first byte is not used).
Communication terminates after the acknowledge bit of
the CRC data. If CRC-8 checksum is not used the
controller may terminate the communication after the
measurement data LSB by keeping ACK high. The device
automatically returns to Sleep Mode after measurement
and communication are completed.
Important: To keep self heating below 0.1°C, SHT7x
should not be active for more than 10% of the time – e.g.
maximum one measurement per second at 12bit accuracy
shall be made.
3.4 Connection reset sequence
If communication with the device is lost the following signal
sequence will reset the serial interface: While leaving
DATA high, toggle SCK nine or more times – see Figure 8.
This must be followed by a Transmission Start sequence
preceding the next command. This sequence resets the
interface only. The status register preserves its content.
Figure 8: Connection Reset Sequence
3.5 CRC-8 Checksum calculation
The whole digital transmission is secured by an 8bit
checksum. It ensures that any wrong data can be detected
and eliminated. As described above this is an additional
feature of which may be used or abandoned. Please
consult Application Note “CRC Checksum” for information
on how to calculate the CRC.
3.6 Status Register
Some of the advanced functions of the SHT7x such as
selecting measurement resolution, end-of-battery notice,
use of OTP reload or using the heater may be activated by
sending a command to the status register. The following
section gives a brief overview of these features.
After the command Status Register Read or Status
Register Write – see Table 4 – the content of 8 bits of the
status register may be read out or written. For the
communication compare Figure 9 and Figure 10 – the
assignation of the bits is displayed in Table 5.
TS
ACK
Bit 7
ACK
0
0
0
0
0
1
1
0
Status Register
Figure 9: Status Register Write
Figure 10: Status Register Read
Examples of full communication cycle are displayed in
Figure 11 and Figure 12.
TS
Wait for
DATA ready
0
0
0
Command
0
0
MSB
LSb
ACK
ACK
LSB
Checksum
Figure 11: Overview of Measurement Sequence. TS = Trans-
mission Start, MSB = Most Significant Byte, LSB = Last
Significant Byte, LSb = Last Significant Bit.
TS
ACK
Bit 7
ACK
Bit 7
ACK
0
0
0
0
0
1
1
1
Status Register
Checksum
DATA
SCK
80%
2
0%
80%
2
0%
1
2
3
2
4 - 8
9
Transmission Start
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 7/12
Figure 12: Example RH measurement sequence for value “0000’0100“0011’0001” = 1073 = 35.50%RH (without temperature
compensation). DATA valid times are given and referenced in boxes on DATA line. Bold DATA lines are controlled by sensor while plain
lines are controlled by the micro-controller.
Bit
Type
Description
Default
7
reserved
0
6 R
End of Battery (low voltage
detection)
‘0’ for VDD > 2.47
‘1’ for VDD < 2.47
X
No default value,
bit is only updated
after a
measurement
5
reserved
0
4
reserved
0
3
For Testing only, do not use
0
2
R/W
Heater
0
off
1
R/W
no reload from OTP
0
reload
0 R/W
’1’ = 8bit RH / 12bit Temp.
resolution
’0’ = 12bit RH / 14bit Temp.
resolution
0 12bit RH
14bit Temp.
Table 5: Status Register Bits
Measurement resolution: The default measurement
resolution of 14bit (temperature) and 12bit (humidity) can
be reduced to 12 and 8bit. This is especially useful in high
speed or extreme low power applications.
End of Battery function detects and notifies VDD voltages
below 2.47 V. Accuracy is ±0.05 V.
Heater: An on chip heating element can be addressed by
writing a command into status register. The heater may
increase the temperature of the sensor by 5 – 10°C
12
beyond ambient temperature. The heater draws roughly
8mA @ 5V supply voltage.
12
Corresponds to 9 – 18°F
For example the heater can be helpful for functionality
analysis: Humidity and temperature readings before and
after applying the heater are compared. Temperature shall
increase while relative humidity decreases at the same
time. Dew point shall remain the same.
Please note: The temperature reading will display the
temperature of the heated sensor element and not
ambient temperature. Furthermore, the sensor is not
qualified for continuous application of the heater.
OTP reload: With this operation the calibration data is
uploaded to the register before each measurement. This
may be deactivated for reducing measurement time by
about 10ms.
4 Conversion of Signal Output
4.1 Relative Humidity
For compensating non-linearity of the humidity sensor –
see Figure 13 – and for obtaining the full accuracy of the
sensor it is recommended to convert the humidity readout
(SO
RH
) with the following formula with coefficients given in
Table 6:
2
RH3RH21linear
SOcSOccRH ⋅+⋅+=
(%RH)
SO
RH
c
1
c
2
c
3
12 bit
-
2.0468
0.0367
-
1.5955E
-
6
8 bit
-
2.0468
0.5872
-
4.0845E
-
4
Table 6: Humidity conversion coefficients
DATA
DATA
SCK
SCK
SCK
DATA
A2 A1
C4 C3 C2 C1 C0 ACK
15 14 13 12 11 10 9 8 ACK 7 6 5
4 3 2 1 0 ACK
7 6 5 4 3 2
1 0 ACK
Transmission Start
Address = ‘000
’
Command = ‘00101
’
12bit Humidity Data
CRC-8 Checksum
Transmission Start
Measurement (80ms for 12bit)
Sleep
(wait for next
measurement)
Idle Bits
Skip ACK to end trans
-
mission (if no CRC is used)
Sensor pulls DATA line low after
completion of measurement
MSb
LSb
MSb
LSb
15 14 13 12 11 10 9 8 ACK
7 6 5 4 3 2 1 0
A2
A1
A0
C4
C3
C2
C1
C0
ACK
7 6 5 4 3 2 1 0 ACK
ACK
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 8/12
Values higher than 99%RH indicate fully saturated air and
must be processed and displayed as 100%RH
13
. Please
note that the humidity sensor has no significant voltage
dependency.
Figure 13: Conversion from SO
RH
to relative humidity
4.2 Temperature compensation of Humidity Signal
For temperatures significantly different from 25°C (~77°F)
the humidity signal requires temperature compensation.
The temperature correction corresponds roughly to
0.12%RH/°C @ 50%RH. Coefficients for the temperature
compensation are given in Table 8.
(
)
(
)
linearRH21Ctrue
RHSOtt25TRH
+
⋅
+
⋅
−
=
°
SO
RH
t
1
t
2
12 bit
0.01
0.00008
8 bit
0.01
0.00128
Table 7: Temperature compensation coefficients
4.3 Temperature
The band-gap PTAT (Proportional To Absolute
Temperature) temperature sensor is very linear by design.
Use the following formula to convert digital readout (SO
T
)
to temperature value, with coefficients given in Table 9:
T21
SOddT ⋅+=
VDD
d
1
(°C)
d
1
(°F)
SO
T
d
2
(°C)
d
2
(°F)
5V
-
40.1
-
40.2
14bit
0.01
0.018
4V
-
39.8
-
39.6
12bit
0.04
0.072
3.5V
-
39.7
-
39.5
3V
-
39.6
-
39.3
2.5V
-
39.4
-
38.9
Table 8: Temperature conversion coefficients.
13
If wetted excessively (strong condensation of water on sensor surface),
sensor output signal can drop below 100%RH (even below 0%RH in some
cases), but the sensor will recover completely when water droplets
evaporate. The sensor is not damaged by water immersion or condensation.
4.4 Dew Point
SHT7x is not measuring dew point directly, however dew
point can be derived from humidity and temperature
readings. Since humidity and temperature are both
measured on the same monolithic chip, the SHT7x allows
superb dew point measurements.
For dew point (T
d
) calculations there are various formulas
to be applied, most of them quite complicated. For the
temperature range of -40 – 50°C the following
approximation provides good accuracy with parameters
given in Table 10:
( )
TT
Tm
100%
RH
lnm
TT
Tm
100%
RH
ln
TTRH,T
n
n
nd
+
⋅
−
−
+
⋅
+
⋅=
Temperature Range
Tn (°C)
m
Above water, 0
–
50°C
243.12
17.62
Above ice,
-
40
–
0°C
272.62
22.46
Table 9: Parameters for dew point (T
d
) calculation.
Please note that “ln(…)” denotes the natural logarithm. For
RH and T the linearized and compensated values for
relative humidity and temperature shall be applied.
For more information on dew point calculation see
Application Note “Introduction to Humidity”.
5 Environmental Stability
If sensors are qualified for assemblies or devices, please
make sure that they experience same conditions as the
reference sensor. It should be taken into account that
response times in assemblies may be longer, hence
enough dwell time for the measurement shall be granted.
For detailed information please consult Application Note
“Testing Guide”.
SHT7x have been tested according to the test conditions
given in Table 11. Sensor performance under other test
conditions cannot be guaranteed and is not part of the
sensor specifications. Especially, no guarantee can be
given for sensor performance in the field or for customer’s
specific application.
Please contact Sensirion for detailed information.
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000 3500
Relative Humidity
SORH sensor readout (12bit)
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 9/12
E
nvironment
Standard
Results
14
HTOL
125°C, 1000 h
Within
specifications
TC
-
40°C
-
125°C, 500 cycles
Acc. JESD22-A104-C
Within
specifications
THU
85°C / 85%RH, 1000h
Within
specifications
ESD immunity
MIL STD 883E, method 3015
(Human Body Model at ±2kV)
Qualified
Latch
-
up
force current of ±100mA with
T
amb
= 80°C, acc. JEDEC 17
Qualif
ied
Table 10: Qualification tests: HTSL = High Temperature Storage
Lifetime, TC = Temperature Cycles, UHST = Unbiased Highly
accelerated temperature and humidity Test, THU = Temperature
humidity unbiased
6 Packaging
6.1 Packaging type
The device is supplied in a single-in-line pin type package.
The sensor housing consists of a Liquid Crystal Polymer
(LCP) cap with epoxy glob top on a standard 0.6 mm FR4
substrate. The sensor head is connected to the pins, by a
small bridge to minimize heat conduction and response
times. The pins are made of Cu/Be alloy coated with
1.3µm Ni and 0.5µm Au, which are soldered to the FR4
substrate by lead-free solder paste. The gold plated back
side of the sensor head is connected to the GND pin. A
100nF capacitor is mounted on the back side between
VDD and GND. The device is fully RoHS and WEEE
compliant – thus it is free of of Pb, Cd, Hg, Cr(6+), PBB
and PBDE.
Size including pins is 19.5 x 5.08 x 3.1mm. Total weight:
168 mg, weight of sensor head: 73 mg.
All pins are Au plated to avoid corrosion. They can be
soldered or mate with most 1.27 mm (0.05’’) sockets, for
example: Preci-dip / Mill-Max R851-83-004-20-001 or
similar.
6.2 Traceability Information
All SHT7x are marked with an alphanumeric, three digit
code on the chip cap – see “B2G” on Figure 1. The lot
numbers allow full traceability through production,
calibration and testing. No information can be derived from
the code directly, respective data is stored at Sensirion.
Labels on the reels are displayed in Figure 14 and Figure
15, they both give traceability information.
14
According to accuracy and long term drift specification given on Page 2.
Figure 14: First label on reel: XX = Sensor Type (71 for SHT71),
NN = Chip Version (04 for V4), Y = last digit of year, RRR =
number of sensors on reel divided by 10 (200 for 2000 units),
TTTTT = Traceability Code.
Figure 15: Second label on reel: For Device Type and Part
Order Number please refer to Table 12, Delivery Date (also
Date Code) is date of packaging of sensors (DD = day, MM =
month, YYYY = year), CCCC = number of order.
6.3 Shipping Package
SHT7x are shipped in 32mm tape at 50pcs each – for
details see Figure 16 and Table 12. Reels are individually
labeled with barcode and human readable labels, see
section 6.2.
Sensor Type
Packaging
Quantity
Order
Number
SHT71
Tape Stripes
50
1
-
100092
-
04
SHT75
Tape Stripes
50
1
-
100071
-
04
Table 11: Packaging types per sensor type.
Dimensions of packaging tape are given in Figure 16. All
tapes have a 7 pockets empty leader tape (first pockets of
the tape) and a 7 pockets empty trailer tape (last pockets
of the tape).
Device Type: 1-100PPP-NN
Description: Humidity & Temperature Sensor
SHTxx
Part Order No. 1-100PPP-NN or Customer Number
Date of Delivery: DD.MM.YYYY
Order Code: 45CCCC / 0
Lot No.: XX0-NN-YRRRTTTTT
Quantity: RRRR
RoHS: Compliant
Lot No.
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 10/12
Figure 16: Tape configuration and unit orientation within tape,
dimensions in mm (1mm = 0.039inch). Leader tape is to the right
of the figure, trailer tape to the left.
Ø1.5 MIN
Ø2.0 MIN
R0.5 TYP
R0.75 TYP
1.75 ± 0.10
0.20± 0.05
14.2
12.00
2.00 ± 0.10
4.00
28.4 ± 0.1
32.0 ± 0.3
20.5
6.4
14.1
5.6
3.6
2.7
0.30
R0.30 MAX
71
B2G
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 11/12
Revision History
Date
Version
Page(s)
Changes
March 2007
3.0
1
–
10
Data sheet valid for SHTxx
-
V4 and SHTxx
-
V3
July 2008
4.0
1
–
10
New release, rework of datasheet
April 2009
4.2
2, 7
Amended foot note 2, communication
diagram changed (Figure 12)
May 2010
4.3
1
–
11
Errors eliminated, information added
–
for details please ask for change protocol.
December 2011
5
1
, 7
-
9
References to V3 sensors eliminated.
Datasheet SHT7x
www.sensirion.com Version 5 – December 2011 12/12
Important Notices
Warning, Personal Injury
Do not use this product as safety or emergency stop devices or in
any other application where failure of the product could result in
personal injury. Do not use this product for applications other
than its intended and authorized use. Before installing, handling,
using or servicing this product, please consult the data sheet and
application notes. Failure to comply with these instructions could
result in death or serious injury.
If the Buyer shall purchase or use SENSIRION products for any
unintended or unauthorized application, Buyer shall defend, indemnify
and hold harmless SENSIRION and its officers, employees,
subsidiaries, affiliates and distributors against all claims, costs,
damages and expenses, and reasonable attorney fees arising out of,
directly or indirectly, any claim of personal injury or death associated
with such unintended or unauthorized use, even if SENSIRION shall be
allegedly negligent with respect to the design or the manufacture of the
product.
ESD Precautions
The inherent design of this component causes it to be sensitive to
electrostatic discharge (ESD). To prevent ESD-induced damage and/or
degradation, take customary and statutory ESD precautions when
handling this product.
See application note “ESD, Latchup and EMC” for more information.
Warranty
SENSIRION warrants solely to the original purchaser of this product for
a period of 12 months (one year) from the date of delivery that this
product shall be of the quality, material and workmanship defined in
SENSIRION’s published specifications of the product. Within such
period, if proven to be defective, SENSIRION shall repair and/or
replace this product, in SENSIRION’s discretion, free of charge to the
Buyer, provided that:
• notice in writing describing the defects shall be given to
SENSIRION within fourteen (14) days after their appearance;
• such defects shall be found, to SENSIRION’s reasonable
satisfaction, to have arisen from SENSIRION’s faulty design,
material, or workmanship;
• the defective product shall be returned to SENSIRION’s factory at
the Buyer’s expense; and
• the warranty period for any repaired or replaced product shall be
limited to the unexpired portion of the original period.
This warranty does not apply to any equipment which has not been
installed and used within the specifications recommended by
SENSIRION for the intended and proper use of the equipment.
EXCEPT FOR THE WARRANTIES EXPRESSLY SET FORTH
HEREIN, SENSIRION MAKES NO WARRANTIES, EITHER EXPRESS
OR IMPLIED, WITH RESPECT TO THE PRODUCT. ANY AND ALL
WARRANTIES, INCLUDING WITHOUT LIMITATION, WARRANTIES
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE, ARE EXPRESSLY EXCLUDED AND DECLINED.
SENSIRION is only liable for defects of this product arising under the
conditions of operation provided for in the data sheet and proper use of
the goods. SENSIRION explicitly disclaims all warranties, express or
implied, for any period during which the goods are operated or stored
not in accordance with the technical specifications.
SENSIRION does not assume any liability arising out of any application
or use of any product or circuit and specifically disclaims any and all
liability, including without limitation consequential or incidental
damages. All operating parameters, including without limitation
recommended parameters, must be validated for each customer’s
applications by customer’s technical experts. Recommended
parameters can and do vary in different applications.
SENSIRION reserves the right, without further notice, (i) to change the
product specifications and/or the information in this document and (ii) to
improve reliability, functions and design of this product.
Copyright
©
2011, SENSIRION.
CMOSens
®
is a trademark of Sensirion
All rights reserved
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phone: +41 44 927 11 66
info@sensirion.com
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