HD2013
- 6 -
V1.6
0.494
0.497
0.500
0.503
0.506
0.509
0.512
0
200
175
150
125
25
50
75
100
R
Cn
I
R
=
11.5 x 10
I
Cn
-5
0.494 +
0.515
0.518
Fig. 2.3 – Normalized resolution (0.5 mm @ 50 mm/h) as a function of the rainfall rate
To correct the measurement depending on the rainfall rate, it is necessary to log, in
addition to the number of pulses, also the instants at which the pulses occur.
Example of measurement correction:
Let’s assume that a rain gauge with nominal resolution R
N
= 0.204 mm @ 50 mm/h
has generated 25 pulses at the frequency of 1 pulse every 25 seconds.
The rainfall rate can be estimated considering the nominal resolution R
N
and the inter-
val between two successive pulses: I ≈ 0.204 x 3600 / 25 ≈ 29.38 mm/h.
From figure 2.2 we obtain the normalized corrected resolution: R
Cn
= 0.198 mm.
The corrected resolution of the rain gauge is: R
C
= R
Cn
x R
N
/ 0.2 = 0.202 mm.
The amount of rain detected is 25 x 0.202 = 5.05 mm.
Rainfall rate (mm/h)
N
o
r
m
a
li
z
e
d
r
e
s
o
lu
ti
o
n
(
m
m
)
