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www.sensirion.com Rev 1.1 – May 2019 1/7
SHTxx and STSxx Design Guide
How to design-in a humidity and temperature sensor.
Overview: The Most Important Design-In Recommendations
1) Sensor has good access to environment
Figure 1: A large opening in the housing provides good access
to environment and allows for air exchange.
2) Sensor is sealed from air entrapped in housing
Figure 2: Sealing of the sensor compartment towards the
remaining housing minimizes the influence of entrapped air on
the sensor.
3) Dead volume enclosed around sensor is small
Figure 3: A small dead volume allows for rapid adaption to
changes in the environment.
4) Sensor is decoupled from heat sources
Figure 4: Decoupling of the sensor from heat sources in the
PCB minimizes the influence of internal heating on the sensor.
Introduction
The accuracy of a measurement does not just depend
on the sensor accuracy itself but also on the set up of the
sensing system. The SHTxx sensors sample relative
humidity and temperature of their direct environment. It
is thus important that the local conditions at the sensor
correspond to the conditions under test. Figure 1 to Figure
4 show the most important design-in recommendations
to ensure good sensor performance: access to
environment, sealing from entrapped air in the housing,
small dead volume and decoupling from heat sources.
The subsequent pages contain more in-depth
descriptions of the design-in recommendations together
with many practical examples.
For proper measurements using SHTxx sensors,
temperature and relative humidity (RH) deviations
between the sensor and the environment must be
avoided.
A usual root cause for temperature deviations are heat
sources, while RH deviations are mostly caused by
temperature deviations as well as slow response times.
Please note that every temperature deviation will cause
RH deviations due to the temperature dependence of the
Preface
The SHTxx are humidity and temperature sensors of
high quality. The digital interface and factory calibration
allows a fast and easy implementation as well as full
interchangeability. In order to take full advantage of their
outstanding performance and features a number of
housing and PCB design rules
need to be considered. This document lists this design
rules and provides help during design-in phase. Please
note that unbeneficial housing and/or PCB designs may
cause significant temperature and humidity deviations
as well as highly increased response times.
