Topic: WH40 vs WH65 Rain Measurements

[LazyDogFarms]

I'm looking at a possible need to calibrate my WH40 due to under-reporting rainfall as well.  I've got a manual gauge I've mounted nearby to check over a few rainfall events to get an average differential between that gauge and the WH40.

Ecowitt has indicated that a single tip of the bucket equals 0.1mm of rain and that three tips equal .01 inch of rain.  So if the WH40 can "process" only 50 tips per forty-nine second reporting period, by my calculations the rainfall rate would have to be in excess of twelve (12) inches per hour (or 360mm per hour) before it would exceed the fifty tips per forty-nine second period limitation.  Am I wrong about this?   

[ns99]

Agree with your arithmetic. I got similar results and so asked Ecowitt directly what is the maximum rainfall rate the WH40 can recorded. The answer came back:

Thanks for your reply. The maximum rainfall rate is about 8mm/h.
You can use the calibration function to change the rain gain to make it more accurate for heavy rain.
Is that acceptable?
Hope to hear from you soon.

Best Regards,
Lucy

I haven't installed a manual gauge to verify. I've only been collecting what leaves the guage and using the calibration formula in the manual.
My concern about the setting a calibration value is that rain events that currently can be recorded correctly will not over report due to the calibration factor. Doesn't fix problem just changes it, or maybe I don't understand how the calibration factor will work.

[LazyDogFarms]

I don't doubt that Lucy said that but her information doesn't make sense to me.  A rainfall rate of 8mm per hour is the equivalent to just .315 inches per hour.  While my WH40 is new, my previous Fine Offset rain gauge regularly measured rainfall rates of over two inches per hour during heavy downpours. 

A rainfall rate of 8mm per hour is just 1.3333 bucket tips per minute.  That can't be the maximum measurement capability of the WH40.

During a moderate shower the other day, my Ecowitt WH40 measured a rainfall rate of .64 inches per hour (or over 16mm/hour). 



So there must be some miscommunication or misunderstanding somewhere along the line.

[K7RMK]

My WH40 has been mounted next to my manual rain gauge for over half a year now and it has been really accurate. The only time the numbers don't match up within a percent or two is when we get heavy rain and lots of it.

I have my meteobridge setup to email me the last 24 hours total rainfall at 7 AM every morning which is when I check the manual gauge so I can compare notes in real time. Most days with precipitation, the numbers match up identically to the ten thousandth.

My WH40 gain is set to 1.0. I don't believe there is an inherent problem with the WH40 itself unless there have been multiple hardware and/or firmware revisions.

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[galfert]

K7RMK,
I really like your install. Very nice. What does your anemometer install look like? What is inside the SRS100LX and what is inside the RS-00001 radiation shields? WH32 and WH57 sensors?

[K7RMK]

K7RMK,
I really like your install. Very nice. What does your anemometer install look like? What is inside the SRS100LX and what is inside the RS-00001 radiation shields? WH32 and WH57 sensors?

Yes, WH32 and WH57 respectively. My anemometer is installed on the roof. It's a 2 story house and I cut the pole so the anemometer is exactly 10 meters above the ground.
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[galfert]

Spectacular! An exemplary install for sure. Nice work. 

I would make that camera angle with the anemometer in the frame as a weather cam. Nice view.

[funsutton]

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I really like your setup. In fact you've inspired me to get my own separate rain gauge to see how my osprey rain gauge matches up.

I decided to get this one from Amazon: Stratus Precision Rain Gauge

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https://www.amazon.com/Stratus-Precision-Mounting-Bracket-Weather/dp/B000X3KTHS/ref=sr_1_3

It looks similar to the one you have in the photo, is it the same?

[galfert]

Yes it is the same. Notice his peeled off Stratus decal that was relocated to the wood shelf that the PM2.5 air quality sensor is on.

The Stratus manual rain gauge is the reference standard. It is what CoCoRaHS uses. It is also referred to as a CoCoRaHS rain gauge.

[K7RMK]

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I really like your setup. In fact you've inspired me to get my own separate rain gauge to see how my osprey rain gauge matches up.

I decided to get this one from Amazon: Stratus Precision Rain Gauge

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https://www.amazon.com/gp/product/B000X3KTHS/ref=ppx_yo_dt_b_asin_title_o00_s00

It looks similar to the one you have in the photo, is it the same?

I clicked on your link and got this. 
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Yes it's the same one. I report to CoCoRaHS using it.

[funsutton]

Yes it is the same. Notice his peeled off Stratus decal that was relocated to the wood shelf that the PM2.5 air quality sensor is on.

The Stratus manual rain gauge is the reference standard. It is what CoCoRahs uses. It is also referred to as a CoCoRahs rain gauge.

Ah. Then I guess I got lucky and picked the right one. Woot!

I clicked on your link and got this. 
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Yes it's the same one. I report to CoCoRaHS using it.

Yikes! I thought I was the only one that could see that. I changed the link above, not that it matters much. But that is truly weird.

EDIT: Oh wait. That says Sept and 2019. I saw the 22 and freaked out for a second. Thought you were seeing my info. Nevermind!

[LazyDogFarms]

We finally had some rain last night so I was able to compare the readings of the WH40 with a manual gauge.  I also compared them to the rain gauge of my WS-2080 which I still have up and running right now as a backup in a different section of our orchard.

The manual gauge showed that we received .40" inch of rain while the WH40 was at .35" and the gauge on my WS-2080 showed .37" of rain.  Not bad.  I'll watch it over a few more rain cycles, last night was a downpour and I'd like to see the accuracy in a gentle steady rain.

[ns99]

Had first heavy rain since installing manual gauge. Manual gauge recorded 33mm, WH40 21.9. At one point the rain was very heavy ~24mm/hr according to weather radar for 10 mins.
In my case, I'm happy with the accuracy of the WH40 during gentle rain events, although I haven't had a long (+1 hour) gentle rain. The problem is with heavier rain - the WH40 has been reporting 50-66% of actual.
Since first posting, and prior to latest rain event, I have upgraded WiFi f/w (1.4.0 -> 1.5.2) & base station f/w (1.6.0 -> 1.6.4).
Noticed at one point that signal strength was down to 1 bar so I realigned the WH40 so the transmitter is in direct line to base station. Previously the collector was between the transmitter and base.
And of course a few power-ups on both WH40 and base for good measure

[galfert]

Since first posting, and prior to latest rain event, I have upgraded WiFi f/w (1.4.0 -> 1.5.2) & base station f/w (1.6.0 -> 1.6.4).
Noticed at one point that signal strength was down to 1 bar so I realigned the WH40 so the transmitter is in direct line to base station. Previously the collector was between the transmitter and base.
And of course a few power-ups on both WH40 and base for good measure

The signal strength on Fine Offset stations is not real signal strength. What you see as signal strength is just the summation of the last few received RF broadcasts from the sensor. Meaning that if 1 out of 4 of the last broadcasts was not received then you would see 3 bars. But in all likelyhood what you saw as a single bar was because you had just firmware flashed or just power cycled the console and it had just started counting broadcasts. The console either receives the signal or it doesn't. There is no RF db loss signal strength measuring going on. Sure it is deceiving to see the console represent it as incrementing signal bars that we are used to for things like WiFi and cellular networks but sadly this is not the case here with these weather stations.

[KD7GFL]

Currently my WH65 (WS-2902A) is showing .64 since midnight and my new WH40 is showing .48 which is a 25% difference.

Not happy with an inaccurate rain gauge.

[Platokidd]

Currently my WH65 (WS-2902A) is showing .64 since midnight and my new WH40 is showing .48 which is a 25% difference.

Not happy with an inaccurate rain gauge.

That's about how far my WH40 was off. Changed the rain offset to 1.42 and now it seems to be okay for now.

[WXDA]

@K7RMK

What a fantastic setup. With the anemometer 10m up, how did you accurately get it pointing north, and how do you get up there/get it down to maintain it?

[LazyDogFarms]

I've now had four rain events since installing my new Ecowitt weather station, including the WH40.  Thus far over the four observations, it appears that my rain gauge under-reports the actual rainfall by just 5%.  Setting the calibration at 1.05 has, over the past two rain events (one was a mix of downpour and steady moderate rain and one was just steady gentle rain), resulted in the WH40 reported rainfall matching the actual rainfall.  Hopefully that level of accuracy will hold over the long-term.

[ivano]

 Ma per confrontare i due pluviometri , li mettete accanto ed alla stessa altezza? No perché altrimenti stiamo parlando del nulla , il WH40 è abbastanza preciso ed è risaputo ho visto confronti con altri pluviometri più costosi e si è difeso alla grande , i 40 euro spesi , sono spesi bene , alla grande direi 

[LazyDogFarms]

Ma per confrontare i due pluviometri , li mettete accanto ed alla stessa altezza? No perché altrimenti stiamo parlando del nulla , il WH40 è abbastanza preciso ed è risaputo ho visto confronti con altri pluviometri più costosi e si è difeso alla grande , i 40 euro spesi , sono spesi bene , alla grande direi 

(Translated to English:  But to compare the two rain gauges, put them next to them and at the same height? No because otherwise we are talking about nothing , the WH40 is quite accurate and it is known I have seen comparisons with other rain gauges more expensive and it defended great , the 40 euros spent, are spent well, great I would say

Yes, the comparison gauge should be mounted very close in proximity to the WH40 and at the same height for most accurate results.

[mark014]

Thanks for your reply. The maximum rainfall rate is about 8mm/h.

This must be some kind of misunderstanding. I have not done any calibration of the rain gauge. Such a torrential rain occurred quite recently.
On June 26, 2020, after 3 p.m., 26 mm of rain fell during the T-storm only in half an hour. I was not at home then, I know there were flooding in the area. Such intensity has not happened here for a long time. And on ecowitt.net I have an intensity of 89.4 mm/h (on WU 85.19 mm/h).


The Ambient Weather station WS-2902 by the lake (approx. 300 m to the west) recorded a slightly higher sum, 27.43 mm, that day, but it was still similar.

Sudden jump in soil moisture:


This was the state of the manual rain gauge on that Friday, probably from Monday (also placed a meter above the ground):

From the total of 5 days of rainfall measured WH40 is 36.5 mm. Overall, that was fine to me.

During the last long rains, I had the impression that the WH40 rain gauge was overestimating the results.

On Monday and Tuesday I had the rainiest 2 days on my station since 2013. There was 28.4 mm of rain on Tuesday, and adding Monday's rain it was 56.3 mm altogether. That's what the WH40 Ecowitt wireless rain gauge has measured.

However, a manual garden rain gauge collected approx. 51 mm, even the scale has run out.


 The single-unit Ambient Weather WS-2902 station in the area (about 300 meters from me) showed 49 mm. The wide WH40 funnel catches rainfall very effectively to me. There is also an aluminum spiral that may minimize reflection of raindrops.

[KD7GFL]

I received my new Stratus gauge on Monday and verified with it during a storm that evening that my WH40 was under reporting substantially. When I compared them during a break in the rain, the Stratus had exactly .50" and my WH40 had only reported .31"   

Seeing no other good options, I made an adjustment to the "Rain Gain" in the calibration settings of my GW1000. I did not make any adjustment to my H2551-C console so I will be able to compare readings without a gain adjustment to my GW1000 which will be adjusted.  I will need to wait for another rain or two to tweak the gain level to see if I can get the WH40 readings to match more closely with the Stratus.

I hope a new improved funnel is in the works and that resolves the issue.  I would not recommend the WH40 as it is right now based on my experience.   

Has there been any new discussions with Ecowitt on this?  Seems to me resolving an extreme inaccuracy issue with a primary sensor already in the field (and thought to be reliable) would be a priority over new projects. 

[KD7GFL]

For comparison, Rain Collector Tops for WH65, WH40, and Stratus rain gauge side by side.

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[john21283]

Hi all

I am new to this forum (first post).

I live in Sooke (where the rainforest meets the sea) on the west coast of Vancouver Island in British Columbia.

The west coast is often called the “wet coast” but we have relatively hot dry spells in the summer, so we irrigate our lawns and garden. We pay for our water – irrigation is costing us about $30/week this summer. I have been estimating our irrigation needs by calculating a water balance (evapotranspiration - rain = irrigation need) using data from nearby stations on WU. However, we are higher and further from the sea than those stations and have a microclimate.

I am planning to install an Ecowitt based system (GW1000 with WH31, WH40 and WH51 soil sensors) to get more efficient use of water, so I was disappointed to see the comments on this thread about the accuracy of the WH40).

On www.wmo.int I found a draft of Chapter 6 Measurement of Precipitation. This WMO document references Sevruk, B. and V. Nespor, 1994: The effect of dimensions and shape of precipitation gauges on the wind-induced error; Global Precipitation and Climate Change (M. Desbois and F. Desalmand, eds.). NATO ASI Series, Springer Verlag, Berlin, I26:231–246.

The WMO document and Sevruk and Nespor list the important requirements for precipitation gauges including:

The collector should be designed to prevent rain from splashing in and out. This can be achieved if the vertical wall is sufficiently deep and the slope of the funnel is sufficiently steep (at least 45%). Suitable arrangements are shown in Figure 6.2;

Copy of Figure 6.2 attached.

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Based on the photos posted by KD7GFL the Stratus gauge appears to meet this requirement but the WD40 does not. The WD40 manual shows that the funnel can be removed easily. I hope that Ecowitt can make a new funnel meeting the WMO requirements given above.

[galfert]

Welcome to the forum. Great information. I do hope that Ecowitt gets this fixed right.

The same information is available in this document (Chapter 6 - ~ page 139):
https://www.weather.gov/media/epz/mesonet/CWOP-WMO8.pdf