Troubleshooting guide

T/H Sensor – General
General Description
While not officially disclosed, it is widely understood that Davis has used the Sensirion SHT-1x series of
temperature/humidity (T/H) sensor elements in all VP2 weather stations manufactured since 2006 (and also
in the Vue model). This is an integrated digital sensor that delivers its data on an interface similar (but not
identical) to the I2C protocol.
The Sensirion sensor element is mounted on Davis’s own small PCB assembly using surface mount
methodology and the T/H chip is therefore not suitable for user replacement by traditional hand-soldering
techniques. Exposed tracks and connections on the PCBA are thoroughly protected from moisture ingress
by epoxy-type coating.
Sensirion sensor elements
There are three types of SHT-1x sensor element made by Sensirion, SHT-10, SHT-11 and SHT-15 which
are identical in general design, but with progressively better accuracy specifications. All three sensors share
the same overall characteristics, with an operating temperature range of -40°C to (nominally!) +100°C and
relative humidity (RH) covering the full range of 0-100% RH. See accuracy profiles for temperature (right)
and RH (left) in the graphs below.
This sensor
family is
designed
with an
optimum
temperature
accuracy at
25°C and
accuracy steadily decreases away from this central design temperature. In other words, the accuracy
specification typically quoted will only be fully valid at 25°C and accuracy will be lower away from the
design temperature. Also, with this profile, it is inevitable that potential inaccuracy will be somewhat greater
at low temperatures (eg -20°C), which are relatively commonplace in winter, than at the maximum
temperature reached across most of the world (eg 45°C).
Prodata Weather Systems Davis Weather Stations KB - Prodata Weather Systems - 1
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