How do wireless rain gauges work?

[muncybob]

I got one for Christmas last year and just took it out of the box to install batteries and set outdoors. The innards have a "see-saw" type of device that collects the rainwater and self empties. This seems to be purely mechanical in nature and I cannot see how it measures anything. Also the battery housing is in there but the 2 do not seem to be connected to each other in any way. For the life of me I cannot see how this thing will measure rainfall but the other day we had a trace amount overnight and there it was on my indoor device showing .02" of rain!

 

[granpajohn]

Back in the day, these where known as "tipping bucket" gauges. The little see-sawing bucket tips when it gets full of 0.01" of rainfall. Count the tips, (electronically), and you have the amount of rain. I have never seen one perform as well as a manual gauge over long periods. They do have some use however.

A couple years ago, I replaced my old temperature station with a Davis Vantage Vue wireless which also has a rain collector. This style is known as "tipping spoon", but I think the theory is the same as for the older style. I still do my rain observation with a standard old fashioned gauge.

Bottom line...the new electric device is not as accurate as the old style. Especially in freezing weather, and in fact, a heater is available for those that use these in the winter. However, it is a real cool gadget, and it is nice to look at the display from the dry comfort of the house. Just don't trust it too far.

I don't think I recommend the Davis Vue because mixing rain, temp, and wind all in the same instrument makes too big a compromise. It has to be too low for wind; (supposed to be 3 meters high), or too high for temp, or too shady for rain, etc.
Your location may vary. My gauge requires constant cleaning because of my trees.

Sorry for the long reply. I think a good explanation can be found on the Davis website.

 

[begreen]

Our Davis unit has been working great for a few years now.

 

[granpajohn]

(Replying to see if I get email notification.)

 

[muncybob]

I understand how the tipping mechanisim works as far as emptying, but I just cannot see where there is any connection in it to the battey compartment so that it can "read" the number of tips. I must be missing something....

 

[begreen]

It depends on the sensor. Here's some info on the topic for a tipping bucket which is the common method. Other's use a strain gauge to measure the weight:
http://weather.about.com/b/2007/06/22/how-weather-instruments-work-lesson-1-rain-gauges.htm

 

[muncybob]

Interesting. I'll be taking it apart again to look a little closer.

 

[semipro]

I understand how the tipping mechanisim works as far as emptying, but I just cannot see where there is any connection in it to the battey compartment so that it can "read" the number of tips. I must be missing something....

It might be as simple as a magnet and reed switch. The magnet would be embedded in the tipping arm and the reed switch (or other magnetic sensor) would be mounted where the moving magnet in the arm passes by it.

It could be optical too where the tipping arm breaks or reflects an infrared or visible light beam.