SUBYDAZZ wrote:
OK, so by adding a larger catchment area and using the calibration factor in Cumulus to compensate for this (eg: If I triple the catchment area of my gauge and then go under Multipliers for rainfall in Cumulus Calibration and put in 0.33) then it will be more sensitive to smaller amounts of rain and variations in the rain rate?
So far as I see it, this should give me slightly more accurate data with respect to having less likelihood of say 0.1 or 0.2mm of rain not being counted because previously it would only measure at least 0.3mm, and thereby giving me nil rain.
I take your point though on the accuracy of the device as far as measurement goes, if the original gauge is not perfectly accurate (and of course it wouldn't be as it's hardly a precision instrument) then any error will be propagated if you go changing the catchment area etc.
With respect to heavy rain, if you have a large catch area does this cause any problems like the reservoir overflowing because the bucket can't tip fast enough or any spillage through the bucket area as a result of the moving bucket itself?
Hi Subydazz, I bench tested my WH1081 after I had increased the catchment area 3 times (55cm2 to 165cm2) and found that each tip (0.1mm) was (trying to remember.....) 12 drops, and that I had no issue with wasted drops (a drop falling into the bucket that was already tipping) up to a rate of 50mm/hr. However, upto 130mm/hr you would get a drop wasted, which would be a 1/13 or 7.7% under reading. Any rate way above this you would probably get a 15.4% under reading. Out of 16 days I've been using Cumulus in December, I had 12 rain days of which 3 times I had it go over 50mm/hr (and up to 118mm/hr). I am currently happy with this trade off. I also like the fact that not only is it more sensitive and accurate (bench tested below 50mm/hr), it also records rain earlier (and sets of my voice confirmation alarm! He he
) Obviously everyone will be different. If you never get above 50mm/hr then do it. If you always get above 50mm/hr, or crikey! 130mm/hr, then you may want to think twice.
I've added a photo. My mod is in two parts. The first mod was to prevent splash out by increasing the wall height (100mm). The 2nd part (done later) was to increase the catchment area. To make the rectangle (50mm x 110mm) proportionate I just made the larger area (50mm x the square root of 3) x (110mm x the square root of 3) using laminating sheets. To make them stronger I laminated a laminating sheet for each side and hot glued them together. It's very strong and total cost was $2 for 9 sheets (the first part was only made with one sheet). I found that making the area excactly 3 times bigger, then using a Calibration multiplyer of 0.33 to give a 0.1mm reading is very neat. I have read others make mods and get each tip of the bucket giving a funny reading like 0.111mm? Weird. If your area is slightly under, you can modify the tipping bucket to make it more accurate (initially mine, unmodified, was 9% under).
Michael (Palmerston, NT, Australia)
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. Well done.