Sensors used with automatic weather stations, Standard sensors – Casella CEL Automatic weather station User Manual

Page 19

SENSORS USED WITH AUTOMATIC

WEATHER STATIONS

The Automatic Weather Station may be equipped with sensors to measure the
following parameters.

Air temperature*
Relative humidity*
Wind speed
Wind direction
Solar radiation
Barometric pressure
Rainfall (separate tipping bucket unit)
Soil temperature
Leaf wetness
Surface (Grass) temperature
Gas
Noise
Tension (tensiometer).

Note that Casella CEL equipment is guaranteed for 12 months from date of
dispatch, with the exception of the actual humidity sensing element. It is
impossible for Casella to control or know the environment in which the sensing
element has been used in relation to its performance constraints.

3.1

Combined Air Temperature and Relative

Humidity Sensor

The combined air temperature and relative
humidity sensor is installed within a single
radiation screen that is mounted on a
bracket below the sensor cross arm. Both
transducers are unaffected by condensation
and are resilient to airborne pollution.

The hygrometer is of the

capacitative type and is largely free from
drift. It offers high repeatability over large
ranges of humidity for long periods.

The temperature sensor is based

upon a platinum resistance element to
BS1904, DIN 43760, and incorporates
linearisation electronics within the sensor.
The output from the temperature sensor is
used to compensate the hygrometer for temperature effects.

Outputs from both of these sensors are led to a terminal box on the

sensor cross arm, from where a single sensor cable is taken to the 7-pin socket
on the bottom panel of the environmental case.

3.1.1

Temperature Sensor Specification

Part number:

R0738B

Sensor type:

Thin film platinum resistance

Measurement range:

-40°C to 60°C

Accuracy:

±0.3°C at 0°C
±0.55°C at 50°C

Operating Temperature

-40°C to +60°C

Standard Sensors

Note*:

Air temperature and relative humidity are measured by a combined sensor.

01056

Combined temperature and relative

humidity sensor

Page 19 of 34

Automatic Weather Station
Assembly & Commissioning Handbook