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SHT3x-DIS Series Datasheet

Sensirion AG

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Datasheet

www.sensirion.com Version 1.2 – May 2010 1/3
Testing Guide
For SHTxx Relative Humidity & Temperature Sensor Series
Sensor Testing and Qualification
For calibration and end testing of RH sensors
Sensirion is using expert calibration equipment and
procedures to guarantee highest precision and
reliability. In order to ensure consistent testing of
Sensirion’s SHTxx relative humidity & temperature
sensors the following preparing items should be
carefully considered:
a) Test Objects: The test series should consist of
at least 5-10 sensors, which should be taken
out of the original packaging.
b) Conditioning: Make sure that sensors have not
been contaminated prior to the testing. Original
packaging should not have been fixed with
scotch tape, packaging should not have been
stored in plastic bags. If you are unsure
whether sensors might have been
contaminated or not, follow re-conditioning
procedure (80-90°C [176-194°F] at < 5%RH for
24h (baking) followed by 20-30°C [70-90°F] at
> 74 %RH for 48h (re-hydration).
c) Re-hydration after soldering: In case sensors
have been soldered to a PCB board please
make sure that re-hydration procedure (20-
30°C [70-90°F] at >74%RH for 48 hours) has
been applied after soldering.
d) Test set-up: Make sure that test and reference
sensor experience equal humidity and
temperature conditions. If possible apply a
professional humidity chamber. If such a
chamber is not available put the reference and
test sensor into a closed box and give the set
up time to homogenize. Please make also sure
that in the humidity housing there are no
humidity absorbing materials present near the
sensors - materials like silicone sealing, rubber,
etc.
e) Reference sensor: The reference sensor should
be of high reliability. If possible apply a dew
point mirror or recently calibrated RH probes.
Testing RH Accuracy
It is recommended to run the following test profile:
Set temperature to 25°C (77°F) and run a low
medium high RH profile (e.g. 15% 50% 90%)
and check hysteresis with a high medium low
RH profile (e.g. 90% – 50% – 15%). See also Figure
1. Allow at least 45 minutes settling time at each
relative humidity set-point, before starting a
measurement.
0%
20%
40%
60%
80%
100%
10%
30%
50%
70%
90%
90%
70%
50%
30%
10%
RH set point profile (%)
Measured RH (%)
-1.6%
-1.4%
-1.2%
-1.0%
-0.8%
-0.6%
-0.4%
-0.2%
0.0%
0.2%
10%
30%
50%
70%
90%
RH set point profile (%)
RH Deviation (%)
Figure 1 Top Panel: Measurement profile for accuracy
testing (full squares: reference, open diamonds: test
sensor). Lower Panel: RH deviation profile, full line:
ascending order, hatched line: descending order.
IMPORTANT: Relative humidity is highly
temperature dependent. During the measurement
the temperature of reference and test sensor must
show the same value to make RH values
comparable. For your test records it is highly
Introduction
This Qualification Guide defines how Sensirion is testing the various performance parameters of humidity and
temperature sensors. Furthermore, it shall help to test and qualify the sensors reliably in due time. It is of great
importance that all applicable documents (Datasheet, Users Guide and Handling Instructions) are carefully
studied before integration, testing and qualification of the sensor.
Testing Guide for SHTxx Sensors
www.sensirion.com Version 1.2 – May 2010 2/3
recommended to note RH and T for each set-point
and sensor.
It is also recommended to operate the SHTxx
sensors with EK-H3 or EK-H4 in order to avoid
communication or conversion errors.
Testing RH Response Time
For properly measuring RH response times a test
set-up shall guarantee a step function from dry air to
humid air at the very same temperature, or vice
versa. Therefore, the following test set-up is
recommended – compare with Figure 2. The sensor
is placed into a small box. Across a rotary valve this
test chamber shall be fed with dry air taken from
compressed, oil-free air – and humid air – taken
from a humidity chamber. As the compressed air
cools down with expansion, the temperature shall
be brought to room temperature by a heater. The
heater alternatively can be placed between air bottle
and rotary valve or between rotary valve and test
chamber. The tubing between the valve and the test
chamber shall be kept as short as possible. This
allows for an abrupt change from dry to humid air.
Figure 2 Response time test set up. Dry air from
compressed air is blown into test chamber with sensor
a heater makes sure the air is at room temperature. With
a rotary valve the relative humidity is taken from a
humidity chamber and therefore abruptly changed from
low to high.
To start the measurement blow dry air into the
sensor box and give the sensor time to display a
constant value. It should be in the range of 5 -
10%RH. Control the temperature carefully as well.
Then change the air source abruptly and make sure
the temperature remains constant. In order to avoid
any temperature changes it is recommended to run
the measurement at ambient temperature.
The data should behave roughly inverse
exponential – see Figure 3. The SHTxx sensors
readings shall change 63% of the full RH step within
less than 8 seconds. For example if the RH step is
between 10% and 90% then the RH value shall
read >60% within 8 seconds. Please note, that for
the last few percentages to complete the full step
the response curve will develop with a ilower time
constant.
There is an alternative option to measure response
time in a very simple and effective way – which,
however, may not fulfill scientific standards: Put the
sensor into a humidity chamber with high humidity
(90% for example) or if no humidity chamber is
available, put the sensor into a closed box with an
open glass of water. Make sure that the
temperature inside the chamber or box is equal to
the outside temperature. Start measuring (for
example with the EK-H2 system) and when the
values are high and stable immediately quit the
sensor from the box or chamber and expose it to
the outside conditions. Give the sensor enough time
to stabilize the RH value and this way define the full
RH step. Now, response time can be derived from
the data.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-10 0 10 20 30 40 50 60
Time (s)
Relative Humidity (%)
Humidity Setting
Response Data
Figure 3 Measurement profile of response time testing
RH = 90%
T = 20°C
RH = 5%
Humidity
Generator
Compressed air
Exhaust
Chamber
Rota
ry
Valve
T = 20°C
Testing Guide for SHTxx Sensors
www.sensirion.com Version 1.2 – May 2010 3/3
Revision History
Date Revision Changes
10 March 2008 1.0 First Release
04 September 2008 1.1 Add Section 1.1
5 May 2010 1.2 Complete rework: New title (former title was “Qualification Guide” and more
information how Sensirion does the out going quality test. No changes to the
existing contents.
© Copyright 2010 by Sensirion
CMOSens® is a trademark of Sensirion
All rights reserved
Headquarter and Sales Offices
Headquarter
SENSIRION AG Phone: +41 44 306 40 00
Laubisruetistr. 50 Fax: +41 44 306 40 30
CH-8712 Staefa ZH info@sensirion.com
Switzerland http://www.sensirion.com/
Sales Office USA:
SENSIRION Inc. Phone: +1 805 409 4900
2801 Townsgate Rd., Suite 204 Fax: +1 805 435 0467
Westlake Village, CA 91361 michael.karst@sensirion.com
USA http://www.sensirion.com/
Sales Office Japan:
SENSIRION JAPAN Co. Ltd. Phone: +81 3 3444 4940
Postal Code: 108-0074 Fax: +81 3 3444 4939
Shinagawa Station Bldg. 7F, info@sensirion.co.jp
4-23-5, Takanawa, Minato-ku http://www.sensirion.co.jp
Tokyo, Japan
Sales Office Korea:
SENSIRION KOREA Co. Ltd. Phone: +82 31 440 9925~27
#1414, Anyang Construction Tower B/D, Fax: +82 31 440 9927
1112-1, Bisan-dong, Anyang-city info@sensirion.co.kr
Gyeonggi-Province http://www.sensirion.co.kr
South Korea
Sales Office China:
Sensirion China Co. Ltd. phone: +86 755 8252 1501
Room 2411, Main Tower fax: +86 755 8252 1580
Jin Zhong Huan Business Building, info@sensirion.com.cn
Futian District, Shenzhen, www.sensirion.com.cn
Postal Code 518048
PR China
Find your local representative at: http://www.sensirion.com/reps

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