User manual

1-Wire Application Guide v1.04 Page 22 of 41
Indoor placement is also critical – don’t install non-HIH4021 sensors in a wet
environment, for example a bathroom shower, since the humidity sensor will
eventually fail.
Most of the sensor connectors will eventually corrode if exposed to high humidity
or corrosive environments, which will lead to false or missing readings.
When used with a TEMP08, set the DS2438 type to “H” (humidity).
3.7 Barometric Sensor
An important weather parameter is air pressure. The absolute reading is not
nearly as significant as the change in the reading, since rising or falling air
pressure will indicate a change in weather.
Figure 14 1-Wire Barometric Sensor
Figure 14 shows the original concept design of a barometric sensor. This design
was not overly practical since the working range of the Motorola pressure sensor
used was very narrow, so David Bray and Jim Jennings modified the design to be
the one shown in Figure 15.