17-03-2017, 03:04
Well, the only thing similar to a datasheet for the Fine Offset rain gauge that I can found, is this document from Argent Data Systems which refers to a weather station which uses Fine Offset sensors.
In this document we can read:
Rain Gauge
The rain gauge is a self-emptying tipping bucket type. Each 0.011”
(0.2794 mm) of rain causes one momentary contact closure that can
be recorded with a digital counter or microcontroller interrupt input.
The gauge’s switch is connected to the two center conductors of the
attached RJ11-terminated cable.
Also, we can find on Cumulus forum, some tests done by individuals:
The bucket needs 1.5 ml water to tip it (result of 3 tests using a syringe and counting the number of tips to take 7.5 ml = 5, 7.5/5 = 1.5).
1.5 ml divided by 55 cm^2 gives 0.0273 cm or 0.273 mm of rainfall per tip of the bucket not 0.3 mm as used in all the rainfall calculations.
which seems to confirm, that the value of each tip bucket expressed on the Argent data Systems documents is the correct value. However, as the Fine Offset rain gauges have the well know problem of under reading (specially during heavy rain), to compensate this, commonly the value of 0.3mm is used, which increases the readings by around 9%
In this new software version, I opted to use the factory value of 0.2794mm rounded to 0.280mm
In this document we can read:
Rain Gauge
The rain gauge is a self-emptying tipping bucket type. Each 0.011”
(0.2794 mm) of rain causes one momentary contact closure that can
be recorded with a digital counter or microcontroller interrupt input.
The gauge’s switch is connected to the two center conductors of the
attached RJ11-terminated cable.
Also, we can find on Cumulus forum, some tests done by individuals:
The bucket needs 1.5 ml water to tip it (result of 3 tests using a syringe and counting the number of tips to take 7.5 ml = 5, 7.5/5 = 1.5).
1.5 ml divided by 55 cm^2 gives 0.0273 cm or 0.273 mm of rainfall per tip of the bucket not 0.3 mm as used in all the rainfall calculations.
which seems to confirm, that the value of each tip bucket expressed on the Argent data Systems documents is the correct value. However, as the Fine Offset rain gauges have the well know problem of under reading (specially during heavy rain), to compensate this, commonly the value of 0.3mm is used, which increases the readings by around 9%
In this new software version, I opted to use the factory value of 0.2794mm rounded to 0.280mm