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1-100707-01 View Datasheet(PDF) - Sensitron

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Description
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1-100707-01
SENSITRON
Sensitron SENSITRON
1-100707-01 Datasheet PDF : 12 Pages
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Datasheet SHT21
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
S10000000 11100111
I2C address + write
Read Register
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
S10000001 00000010
I2C address + read
Register content
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
S10000000 11100110
I2C address + write
Write Register
55 56 57 58 59 60 61 62 63
00 000011 P
Register content to be written
Figure 16 Read and write register sequence – grey blocks are
controlled by SHT2x. In this example, the resolution is set to 8bit
/ 12bit.
5.7 CRC Checksum
For implementing CRC8 checksum please refer to
Wikipedia (http://en.wikipedia.org/wiki/crc8).
5.8 Serial Number
SHT21 provides an electronic identification code. For
instructions on how to read the identification code please
refer to the Application Note “Electronic Identification
Code” – to be downloaded from the web page
www.sensirion.com/SHT21.
6 Conversion of Signal Output
Default resolution is set to 12 bit relative humidity and 14
bit temperature reading. Measured data are transferred in
two byte packages, i.e. in frames of 8 bit length where the
most significant bit (MSB) is transferred first (left aligned).
Each byte is followed by an acknowledge bit. The two
status bits, the last bits of LSB, must be set to ‘0’ before
calculating physical values. In the example of Figure 13
and Figure 14, the transferred 16 bit relative humidity data
is ‘0110’0011’0101’0000’ = 25424.
6.1 Relative Humidity Conversion
With the relative humidity signal output SRH the relative
humidity RH is obtained by the following formula (result in
%RH), no matter which resolution is chosen:
RH
6
125
SRH
216
In the example given in Figure 13 and Figure 14 the
relative humidity results to be 42.5%RH.
The physical value RH given above corresponds to the
relative humidity above liquid water according to World
Meteorological Organization (WMO). For relative humidity
above ice RHi the values need to be transformed from
relative humidity above water RHw at temperature t. The
equation is given in the following, compare also
Application Note “Introduction to Humidity:
RH i
RHw
exp
βw t
λw t

exp
βi
λi
t
t

Units are %RH for relative humidity and °C for
temperature. The corresponding coefficients are defined
as follows: βw = 17.62, λw = 243.12°C, βi = 22.46, λi =
272.62°C.
6.2 Temperature Conversion
The temperature T is calculated by inserting temperature
signal output ST into the following formula (result in °C), no
matter which resolution is chosen:
T
46.85
175.72
ST
216
7 Environmental Stability
The SHT2x sensor series were tested according to AEC-
Q100 Rev. F qualification test method. Sensor
specifications are tested to prevail under the AEC-Q100
temperature grade 2 test conditions listed in Table 917.
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.
Environment Standard
Results18
HTSL
125°C, 1000 hours
Within
specifications
TC
-50°C - 125°C, 1000 cycles Within
Acc. JESD22-A104-C
specifications
UHST
130°C / 85%RH, 96h
Within
specifications
THU
85°C / 85%RH, 1000h
Within
specifications
ESD immunity MIL STD 883E, method 3015 Qualified
(Human Body Model at ±2kV)
Latch-up
force current of ±100mA with Qualified
Tamb = 80°C, acc. JEDEC 17
Table 9: Qualification tests: HTSL = High Temperature Storage
Lifetime, TC = Temperature Cycles, UHST = Unbiased Highly
accelerated Stress Test, THU = Temperature Humidity
Unbiased.
17 Sensor operation temperature range is -40 to 105°C according to AEC-Q100
temperature grade 2.
18 According to accuracy and long term drift specification given on Page 2.
www.sensirion.com
Version 1.0 – January 2010
9/12
 

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