Topic: Electronic Rain guage versus Manual

[DAVE Z]

I have a Vantage Pro 2 weather station bought eight years ago. I am also a volunteer weather observer for the NWS. The NWS provided me with a stainless steel canister with a 8" diameter. I have noticed the VP2 will read much higher precips than the NWS gauge sometimes. Is it possible for the electronic gauge to read higher figures than it should? I checked the cups and they are clean. I would think it would read lower with time.

[ocala]

Yes it can read higher, although generally speaking the Davis usually under reports.
There are adjustment screws under each tipper. Just look for the +/- signs by the screws. Give each side a quarter turn to the minus direction. It will take a few rain events to get it close to your 8 inch gauge.

[Mattk]

Normally the Davis rain gauge under reads but than can be a little dependent on the rain intensity as a tipping type bucket has some variations.

[Dane_B]

First thing I would ask is "how close are the manual and the electronic gauges to one another?".
The reason I ask is my old setup was a Vantage Pro. It was starting to fail so I bought a Vantage Pro2 but it sat new in the box for a few years waiting for the old one to totally quit. I installed the new one a year ago and was sitting back fat and happy until I joined this group. Now I've become more critical of the info reported. Lucky for Me, I was approached by the Township Road and Wastewater Management crews to get a station running for them. We installed it about 2 Mi. from my home as the crow flies.

Back to the question at hand. I now have the luxury to observe 2 separate stations at the same time in a similar location.  I noticed you stated "sometimes". I've observed the two stations are not always reporting the same rainfall and/or rate. They vary +/- and it is not consistently an error in the same direction station to station. This tells not it is not a calibration  error in one station or the other. I DID notice the the Township station gets a lower accumulation in a very light misty drizzle. I do have a rain cone heater installed on that one and thought possibly there was some evaporation. So since snow season is over, I asked them to turn off the heater.
One other difference is I have the AeroCone and they do not since they have the heater.

In last night's light/medium rainfall they are running dead heat.
I guess all that I'm trying to say is it truly and error or is it an inconsistency introduced by some outside influence?

[archae86]

If you had a consistent proportional error observed across a wide range of wind conditions and rain rates you would have a suitable situation for adjustment by calibration. Otherwise you are quite likely in calibrating to tune for agreement in one particular condition which may not be the best overall for your future experience.

[miraculon]

I have a Davis VP2 (with Aerocone for the summer, old cone & heater for the winter). I also have a NovaLynx 8" TBR and a CoCoRaHS gauge. When winds are light and rain is straight down, I have had close agreement between all three (+/- 0.01). When winds are significant they can vary by several hundredths of an inch.

I have calibrated the NovaLynx with their calibrator and checked the Davis against the calibrator as well.

I have a small back yard which violates the placement guidelines for rain gauges.

Having said this, I agree with others that the pre-Aerocone Davis seems to have a propensity for under counting, not over counting when wind is present.

It might be worthwhile inspecting the reed switch and connector in the ISS SIM. Also a frayed and intermittent cable could cause problems if the exposed rain switch wires are contacting each other.

Greg H.

[Mattk]

There is really nothing that can be deduced or assumed from 2 stations 2Mi apart.

[Dane_B]

There is really nothing that can be deduced or assumed from 2 stations 2Mi apart.

During a Summer spotty isolated downpour situation, I would fully agree. In these Spring long term dreary all night/day drizzles, not so much.

[CW2274]

There is really nothing that can be deduced or assumed from 2 stations 2Mi apart.

During a Summer spotty isolated downpour situation, I would fully agree. In these Spring long term dreary all night/day drizzles, not so much.

True, but even in the best of circumstances, I'd never use this comparison for the sake of calibration. Getting a ballpark figure, fine. If you truly want to make a viable comparison, they basically need to be side by side, and at the same height too.

[Dane_B]

There is really nothing that can be deduced or assumed from 2 stations 2Mi apart.

During a Summer spotty isolated downpour situation, I would fully agree. In these Spring long term dreary all night/day drizzles, not so much.

True, but even in the best of circumstances, I'd never use this comparison for the sake of calibration. Getting a ballpark figure, fine. If you truly want to make a viable comparison, they basically need to be side by side, and at the same height too.

And we circle right back around to the first line on my first reply to this thread. Sorry to upset you. Apparently I don't fit in here as I've only made 11 or 12 posts.

[CW2274]

There is really nothing that can be deduced or assumed from 2 stations 2Mi apart.

During a Summer spotty isolated downpour situation, I would fully agree. In these Spring long term dreary all night/day drizzles, not so much.

True, but even in the best of circumstances, I'd never use this comparison for the sake of calibration. Getting a ballpark figure, fine. If you truly want to make a viable comparison, they basically need to be side by side, and at the same height too.

Sorry to upset you.

Ummm, what? I and others here are merely trying to give you the benefit of some really good wisdom here. Do what ya want. Jeez....

[Mattk]

There is really nothing that can be deduced or assumed from 2 stations 2Mi apart.

During a Summer spotty isolated downpour situation, I would fully agree. In these Spring long term dreary all night/day drizzles, not so much.

True, but even in the best of circumstances, I'd never use this comparison for the sake of calibration. Getting a ballpark figure, fine. If you truly want to make a viable comparison, they basically need to be side by side, and at the same height too.

And we circle right back around to the first line on my first reply to this thread. Sorry to upset you. Apparently I don't fit in here as I've only made 11 or 12 posts.

Number of posts has absolutely nothing to do with anything. But there does appear to be a preconceived idea with 2 systems 2 miles apart that have absolutely no relevance to each other in comparative terms. You appear to have made up your mind anyway that somehow you can compare these 2? 

[dalecoy]

[
And we circle right back around to the first line on my first reply to this thread. Sorry to upset you. Apparently I don't fit in here as I've only made 11 or 12 posts.

Number of posts has absolutely nothing to do with anything. But there does appear to be a preconceived idea with 2 systems 2 miles apart that have absolutely no relevance to each other in comparative terms. You appear to have made up your mind anyway that somehow you can compare these 2?

Note that Dane_B isn't the person who started this thread.

But I'll also note that, one summer, I sat and watched it rain rather hard - for about 10 minutes - on the South side of my patio.  While not a drop fell on the North side of my patio.  And is wasn't a big patio, either, nor was there any cover, no trees, etc. etc.