Rain rate

I have a new Tesa WS1081 on an acer one PC running Windows 7 Intel Atom 1.6GH 2 core with 2 GB ram. WD vers 10.37542
I am getting rain rates in excess of 150mm/ hr, in moderate rain.
Example - 0.9mm (3 tips) in 4 minutes is recorded as a rate of 154.29 mm/hr.
I calculate this should be 13.5mm/hr
Advice would be appreciated,
Thank Paul

note that this is an instantenous rain rate
i,e if the rain continued at that rate for 1 hour, then you would get that much in 1 hour
(at that max rain rate)
the current rain rate should be used (its rate per hour)
the other issue is the hardware and how often a new tip is reported to the software,i.e the update rate
on some weather station hardware , its not that often, which will effect the accuracy of the instantenous rain rate (which is based on the time between tips)