Rain Gauge - New version

In early 2012, the rain gauges of Fine Offset weather stations have been modified to improve accuracy.

Previous rain gauges had a very shallow funnel. Rain droplets, particularly large ones, were prone to splattering off the edge after hitting the funnel. In very heavy rain, the gauge would under report the amount of rain.

Taller wall

The new gauge has a taller wall around the top of the funnel. This makes it slightly taller than the old gauge, but the funnel has now been made more shallow to accommodate.

With the new wall, there is less chance of large water drops splashing off the edge and being lost.

It will also help in very heavy downpours. Water flow is limited by the diameter of the funnel hole. In the old gauge, the hole had a crossbar of plastic (to prevent debris from entering). This limited water flow would be a problem in heavy rain, because when the rain rate exceeded the funnel flow, the funnel would fill up and overflow. The new design, with the wall, makes for a deeper water holding capacity, so should not overflow in heavy rain (which usually doesn't last for long anyway). Having said that, the funnel hole in the new gauge is smaller, which lends to becoming more easily blocked. But as with the maintenance requirements of these gauges, it shouldn't be too much more effort to check the hole for blockages as much as the usual checks for spider webs around and under the tipping buckets.

The wall may also help in times of strong winds. Droplets that land in the funnel catchment area are much less prone to being blown back out.

Spirit Level

Another addition is a built-in spirit level. Although small and very limited in accuracy, it may assist with the mounting of the gauge so that it is level. Tipping bucket gauges need to be level and on a sturdy mount for the correct measurement of rain rate. If the gauge is tilted to one side, each odd tip may measure less than than every other even tip.

The gauges also need to be mounted on a support or pole that doesn't move or wobble. Flimsy poles, especially long ones, can move around in the wind. In certain circumstances, the wobbling motion can cause the bucket to tip, thereby falsely reporting rain.

Same Internal Design

Internally, the old and the newly re-designed gauges are the same. Both use the same tipping bucket mechanism and magnet/reed switch to detect each tip. The resolution is unchanged - it is still 0.3mm per tip. But the wall should make the accuracy of the gauge comparable to manual gauges.

It is believed the changes to the rain gauge may be in part due to discussions on internet forums regarding the inaccuracy of these gauges. The manufacturer is probably taking as much notice at what people are saying, as well as direct feedback from distributors and end users alike.

Finally, it is worth noting that these gauges are also used in other weather station models, including those that only measure rain and temperature. On such models, the themometer, transmitter and AA batteries are housed in the rain gauge. The 'fatter' section of the reed switch housing is designed as a battery compartment.

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