The principle behind the operation of this instrument is simple.
How does a rain gauge work?
A tipping-bucket raingauge uses a metallic or plastic twin bucket balance to measure the incoming water in portions of equal weight.
When one bucket is full, its centre of mass is outside the pivot and the balance tips, dumping the collected water and bringing the other bucket into position to collect.
The bucket compartments are shaped in such a way that the water is emptied from the lower one. The water mass content of the bucket is constant (m [g]).
Therefore, by using the density of water (r = 1 g/cm3), the corresponding volume (V [cm3]) is derived from the weight of the water and, consequently, the corresponding accumulation height (h [mm]) is retrieved by using the area of the collector (S [cm2]). The equation is:
Thus, by using the density of water, h is calculated, where 1 mm corresponds to 1 g of water over an area of 10 cm2 .
To have detailed records of precipitation, the amount of rain should not exceed 0.2 mm. For a gauge area of 1 000 cm2, this corresponds to a bucket content of 20 g of water.
The raw output is a contact closure (reed switch or relay contact), so each tip produces an electrical impulse as a signal output which must be recorded by a data logger.