Rain Gauge not sensing rain

[Sneezy24]

Hi folks,

I've got a Maplin W-1081 - had it for quite a few years.

Humidity sensor has not worked for a couple of years, not too bothered about that, but it has now stopped sensing rain!

I have the 'old' style rain-gauge unit (with holes, not grids under the bucket). Electronically it works (if I tip the buckets by hand then it registers on the base unit and in Cumulus. If I pour water in through the lid, it registers and records OK.

However, when it rains - NOTHING!

I've cleaned the whole rain unit, cleaned out the spiders and webs, ensured the sky is clear above (as in no trees!) but still no rain.

I KNOW it rained last night (I'm in Wokingham, it poured all evening and has only just stopped).

Any ideas??

I think it might be time to replace my whole station...

[AllyCat]

Hi,

Possibly the rain is also getting into the cable/connectors. The "pull-up" current from the transmitter is very low (~25 uA) so a slight leakage (through water) can "short-out" the rain sensor switch. However, it happens that my own FO station has a very similar fault, which needed a multimeter to identify:

In my case, even with the Rain cable unplugged, the voltage being output across the "Rain" connector pins is only about 1.25 volts (which is very close to the switch sensing voltage) instead of the expected 3 volts (from the two AA cells). So sometimes it registers rain tips and sometimes it doesn't. Therefore, I plan to "open up" the transmitter box and add a pull-up resistor (from the switch pin to the + battery line). 100 kohms would give a current similar to the design value, but 10k might give more reliable operation, with negligible drain on the battery, since current only flows whilst the seesaw is actually tipping.

Cheers, Alan.

[Sneezy24]

Thanks,

But it works if I pour water through it, and tipping the bucket by hand works.

If I pour water through it will it is raining - it works.....

Baffled!!

[BigOkie]

But if you pour water through it, you're only getting the cone and the tippers wet (and whatever gets wet during the tipper emptying). If it's raining, then the whole unit gets wet.

[Sneezy24]

I tried poring water through when it was raining (hard! anorak with hood needed) and it senses the poured water, but not rain!

[beteljuice]

So ... does it register if you dribble water into the funnel ?

[Sneezy24]

Yes!