ARG100 Tipping Bucket Raingauge
10
Shelf
Support
Bench
Sink
Figure 2 Arrangement for Setting and Calibrating the Raingauge
If N is the number of tips (together with the fractional part left in the one bucket),
the calibration factor (CF) is then
CF = 0.2 (optionally 0.25) x 80/N
For example, if N = 78.8, then
CF = 0.2 (optionally 0.25) x 80/78.8
= 0.203 mm/tip
The amount of rainfall in any particular interval is obtained by multiplying the
number of recorded tips by the calibration factor.
This type of dynamic calibration gives repeatable results indoors, but it is not a
true representation of the gauge’s sensitivity to natural precipitation. Useful
results can be obtained by comparing the output from the ARG100 with the
catches from a standard ‘Snowdon pattern’ gauge (HMSO, 1956) sited nearby; if
this comparison is carried out with care, a calibration factor for natural rainfall
can be calculated from the slope of a graphical plot of (number of tips) against
(catch from Snowdon gauge in mm).
