RAIN GAUGE MEASUREMENT PROBLEM

p.pagliochini

Today I dedicated myself to calibrating the rain gauge. As indicated by the Netatmo instructions, I took my 100ml in a container that pours drop by drop at intervals of 3 seconds per drop.
Now the default value was 1.25478, so it read.
After the whole procedure, the sensor balance clicked 79 times, therefore 100: 79 = 1.2658 for approximation 1.26 I set. It was not that different from the default one.
Here is where something happens that I can't understand.
since I'm stubborn, I poured 100ml into the rain gauge again
With the coefficient set to 1.26 ml per click, if you pour 100 ml of water again, the balance will click 79 times again.

Now let's calculate the rain detected by the Netatmo sensor:

79×1.26=99.54 ml
Let's convert into mm of rain knowing that the rain gauge measures in liters per square meter (mm/m²).
100:0.0046=21.73 mm
​
The value 0.0046 m² comes from the collection area of ​​the rain gauge which has a diameter of about 77 mm
therefore converting the diameter into meters: 0.077 m
I calculate the radius 0.077:2=0.0385
I find its area π×(0.0385)² = 0.00465 let's approximate it to 0.0046.

The problem is that the rain gauge shows me 7ml and not 21.63ml.

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    stevermoor

    Hi I have a similar problem with the rain gauge. I have used it for over a year and need reasonably accurate results (+/- 5%) acceptable.

    We recently had a storm and I recorded 48mm rain. Comparing the rainfall with two other local gauges it was 16% under reading.

    I set about cleaning and calibrating and I made the counts 83mm. (I used pure distilled water. ). I also did the pouring a measured quantity of water and it gave me a consistent result as long as I didn’t pour it too fast or too slow. So the default value of 1.25 ml per rock is probably correct. However my result in use is more like 1.4ml but I. Calibration correct.

    I am now going to conduct a set of tests for different intensities of rain. (I have an Oregan Scentific gauge as well and will compare results. ). I suspect it misses rocks when it’s with very light or very heavy.

    Certain factors could affect it. Light rain surface tension or evaporation. Heavy rain overloading the rocker.

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