Gill Instruments Ltd
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MaxiMet Page 9 Issue 3
Doc. No. 1957-PS-021 May 2018
2.1.5 Barometric Pressure (GMX300, GMX301, GMX400, GMX500, GMX501, GMX531,
GMX541, GMX550, GMX551 and GMX600)
Barometric pressure is provided by a solid-state device fitted onto a board inside a MaxiMet moulding.
2.1.6 Temperature, Relative Humidity and Dewpoint (GMX300, GMX301, GMX400,
GMX500, GMX501, GMX531, GMX541, GMX550, GMX551 and GMX600)
There is internal solid state sensor circuitry contained within the radiation shield that provides digital
output signals for Relative Humidity, Temperature and calculated Dewpoint.
2.1.7 Rain (GMX100, GMX240, GMX400, GMX541, GMX600 (and Gill Spare Part 1957-
PK-073))
Rain drop detection and a reading of Rain level is provided by using an optical infra-red beam sensor. Infra-
red beams bounce off the inner optical surface between transmitters and receivers. Depending on rain
drop levels the intensity of the beams change and internal digital signal processing allows a measurement
of Rain levels to be made. The sensor increments rain detected in default 0.080mm steps but tip size can
be changed. The GMX541 rain gauge is supplied with a 20M lead with 9 way and 4 way connectors fitted.
NOTE: The Optical Sensor provides a General Indication only of rainfall levels for use in situations where
low maintenance is required. Use a tipping bucket or equivalent with a MaxiMet (e.g. GMX531, GMX550-
and GMX551) where reference quality precipitation measurements are required.
2.1.8 Rain (GMX531)
A reading of Rain levels is provided by a supplied remote Kalyx traditional tipping bucket rain gauge. A
switch contact closure provides a connection to the GMX531 through a plug-in connector where a tip
occurs for 0.200 mm of rainfall. For rainfall rates above 120mm/hour and up to 1000mm/hour then
contact EML in the UK for a mathematical correction to readings.
The Kalyx rain gauge is supplied wired to a 20 metre long cable which has a 4-way connector fitted to it
that plugs into a socket in the moulding of the GMX531.
2.1.9 Rain (GMX550 and GMX551)
A Rain Gauge switch contact closure is required to be connected through the 4 way plug-in connector, to
register that a tip has occurred. The default tip size is 0.000mm but this can be adjusted by the user to suit
their supplier rain gauge.
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