Troubleshooting guide

Humidity accuracy has its own characteristic profile: Maximum RH accuracy is attained across a central
band of RH values spanning roughly 20-80% RH. Accuracy then decreases markedly towards 0% and
towards 100% RH. Since fog and heavy rainfall are obviously associated with high RH values, it’s worth
noting that humidity in the range 95-100% is a tricky region to measure accurately and potential errors will
always be higher here. It is not uncommon to find that 98% or 99% is the highest RH value that a station will
display (unless a console offset is deliberately entered).
Davis T/H sensor PCB assemblies
The standard VP2 T/H sensor is part 7346.166 which has now reached revision J. This part is thought to
use the middle-ranking SHT-11 part (SHT-10 being unused by Davis), which is specified as having a typical
temperature accuracy of ±0.4°C (at 25°C) and for humidity of ±3% over 20-80% RH, rising to 5% at 0 and
100% RH. The Vantage Vue is also thought to use this same SHT-11 sensor element.
In 2015, Davis will introduce the option of VP2 stations which use an enhanced T/H sensor and which
therefore presumably uses the SHT-15 sensor element. This option has two main benefits:
• In addition to lowering the typical temperature accuracy at 25°C to ±0.3°C, the SHT-15 has an
altogether shallower temperature/accuracy profile, which offers a roughly doubled temperature
accuracy at eg -10°C and 40°C;
• The baseline RH range of the SHT-15 is ±2% over 10-90% RH and maximum error at 100% RH is
reduced to 4%.
This enhanced T/H sensor is scheduled to be available in the full range of VP2 stations and will also be
available as part 7346.174 as a replacement T/H board for existing VP2 stations. There is no sign that the
enhanced sensor will be available for the Vue stations.
Prodata Weather Systems Davis Weather Stations KB - Prodata Weather Systems - 1
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