Heating Condensate measure in %

[Bernoo]

Hello,
I am new here and have already successfully connected my water meter and gas meter via the Piface.

Now I want to optimize my heating. In addition I wanted to measure the condensate quantity of the gas heating with a rain gauge, and calculate with the gas consumption per hour and show it in percent, with a virtual counter indicate.
Can anyone tell me how this works?

Grettings
Bernoo