28018 Parallax Inc, 28018 Datasheet - Page 5

• Manufacturer Part Number: 28018
• Description: MODULE SENSOR TEMP+HUMIDITY
• Manufacturer: Parallax Inc
• Series: Sensirion SHT11r

Specifications of 28018

• Output Type: Digital - 2-Wire
• Sensor Type: Humidity and Temperature
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

SHT1x / SHT7x Relative Humidity & Temperature Sensor System
3
3.1 Relative Humidity
To compensate for the non-linearity of the humidity sensor
and to obtain the full accuracy it is recommended to convert
the readout with the following formula
Table 6
For simplified, less computation intense conversion formulas
see application note “RH and Temperature Non-Linearity
Compensation”.
The humidity sensor has no significant voltage dependency.
Figure 10 Conversion from SO
3.1.1
For temperatures significantly different from 25°C (~77°F)
the temperature coefficient of the RH sensor should be
considered:
Table 7
This equals ~0.12%RH / °C @ 50%RH
1
www.sensirion.com
RH
RH
Where SO
12 bit
12 bit
SO
SO
linear
8 bit
8 bit
true
Converting Output to Physical Values
RH
RH
=
=
Compensation of RH/Temperature dependency
(T
RH
c
Humidity conversion coefficients
Temperature compensation coefficients
°
1
C
is the sensor output for relative humidity
+
-
25)
c
0.01
0.01
2
c
-4
-4
t
•
1
1
•
SO
(t
1
RH
+
t
+
2
0.00008
0.00128
•
c
0.0405
0.648
3
SO
RH
c
t
•
2
2
to relative humidity
SO
RH
)
RH
+
1
2
RH
:
-2.8 *10
-7.2 *10
linear
c
3
-6
-4
v2.0 March 2003
3.2 Temperature
The bandgap PTAT (Proportional To Absolute Temperature)
temperature sensor is very linear by design. Use the
following formula to convert from digital readout to
temperature:
Table 8
For improved accuracies in extreme temperatures with more
computation intense conversion formulas see application
note “RH and Temperature Non-Linearity Compensation”.
3.3 Dewpoint
Since humidity and temperature are both measured on the
same monolithic chip, the SHTxx allows superb dewpoint
measurements. See application note “Dewpoint calculation”
for more.
Temperatur
VDD
3.5V
2.5V
5V
4V
3V
d
-40.00
-39.75
-39.66
-39.60
-39.55
1
Temperature conversion coefficients
[°C]
e
=
d
1
-40.00
-39.50
-39.35
-39.28
-39.23
d
+
1
[°f]
d
2
•
SO
T
SO
14bit
12bit
T
d
0.01
0.04
2
[°C]
d
0.018
0.072
2
[°f]
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