Contents
MetPak RG User Manual
Last Change
©
Gill Instruments Ltd
12 February, 2013
Page 3
1.1.2
Radiation Shield
The Multi-Plate Radiation Shield protects temperature and relative humidity
sensors from error-producing solar radiation and rain. This shield relies on a
combination of plate geometry, material and natural ventilation to provide effective
shielding.
1.1.3
Temperature and Relative Humidity Sensor with
Dewpoint Output
The Rotronic HygroClip module is a complete
instrument,
with
integrated
temperature
compensation. Calibration data is maintained
within the integrated electronics. It provides
digital output signals for Relative Humidity,
Temperature and Dewpoint to the MetPak RG
Hub box.
Position of Temperature and Relative Humidity
Probe in the Radiation Shield.
1.1.4
Barometric Pressure
Barometric pressure output is provided by a solid-state device fitted on to the
circuit board in the MetPak RG Hub box. Vent to atmosphere is via a Gortex filter
which also protects the pressure sensor from the effects of wind and rain.
1.1.5
Rain Sensor (DIG1 Input)
Rainfall is measured by the well-proven tipping bucket method.
Rain is collected by a funnel and is passed to one of the two
buckets situated at either end of a short balance arm. The
balance arm tips when the first bucket is full, emptying this
bucket and positioning the second bucket under the funnel. The
tipping process repeats indefinitely as long as the rain
continues to fall, with each tip corresponding to a fixed quantity
of rainfall; at each tip the moving arm forces a magnet past a
reed switch, causing contact to be made for a few milliseconds.
The Rain Gauge is connected to the MetPak RG Digital input, which detects when
two dedicated terminals are short circuited (less than 1k ohm).
