User manual

1-Wire Application Guide v1.04 Page 15 of 41
3 Weather Monitoring
3.1 Types of Weather Sensors
1-Wire weather sensors are available from a variety of vendors, including, of
course, Midon Design. All the standard weather parameters can be monitored
with the sensors.
The following sections will describe the available sensors, and the theory of
operation of the sensors.
It should be noted that most, of these sensors might be mounted outdoors, so be
careful with how you mount them and most importantly about the wiring. An
ever-present danger about wiring outdoors is exposure to the elements and
increased exposure to potential lightning strikes. As a general rule you should
disconnect all the sensors whenever lightning is nearby. If you are mounting your
sensors outdoors, also be very aware of any nearby power wires and avoid them.
3.2 Temperature Sensors
There are different types of temperature sensors available for 1-Wire
applications. These include:
3.2.1 DS18S20
This is the ubiquitous sensor and available in many mounting options, ranging
from the bare device to sealed enclosures with connectors.
The DS18S20 offers 9-bit resolution, or a ± 0.5°C precision. Temperatures can
be measured from –55°C to +125°C (-67°F to +257°F). Accuracy is ± 0.5°C (±
0.9°F) from –10°C to +85°C.
3.2.2 DS18S20-PAR
The DS18S20-PAR is identical in performance to the DS18S20, except that it will
only operate in parasitic powering mode. The V
dd
pin is not connected on this
device and is internally connected to the GND pin. This device is not normally
seen in enclosures or connectorized modules and is best suited for on-board
temperature sensing.
3.2.3 DS18B20