[MikeM]

On my Davis Vantage Pro sensor suite the rain gauge came with both imperial and metric adapters.
So I just fitted the metric adapter, as we use the metric standard in South Africa.

Just a note, don't know if it has been mentioned before, you won't be able to use the Davis temp/humid sensor with the Weartherduino. 
The shield can be used though, you just make up a temp/humid sensor of your chose that is compatiple with the WeatherDuino to put into the Davis shield.

[coupe pete]

Thanks. Have just purchased a used Davis Vantage Pro outdoor sensor for about 200 AUD in the US. It will be carried back by a friend returning from US so it will be a while before I can inspect it and see what I got, but fingers crossed.