Initial idea was to create a device which anyone could make. However, after many jugaad tries it was clear that if volunteers make rain gauges, each will have some difference than the other in terms of accuracy and so there will be no way of relying on the data.
So, reluctantly i chose to remove the uncertainty in the design by using a laser cut acrylic design. It is designed to drain with every 1mm of rainfall, i.e. that is the least count.
Here are some pics.
3 plate acrylic design. Receiver of rain is on the top side. It fills a tank on the left. The tank fills only upto where the upward pipe bends down. Thereafter, water auto-drains through the bottom. Two wires for the two electrodes for sensing a draining event.It fits onto a commonly available PVC pipe reducer. A PVC pipe (in background) fits and seals the device completely. The opening rain collector diameter of the reducer is 110mm and the pipe diameter is 63mm. The ratio of volume of rain water collected in the acrylic tank system (just before draining) and the rain collector area is the rainfall measurement, in this case = 1 mm.Another view of the system. Note the collector design.
