Topic: WH40 vs WH65 Rain Measurements

[KD7GFL]

I just did a quick measurement of the top inner diameters.  I was using a tape measure so not exactly precise.

WH65=4 3/8"
Wh40= 7"

[LazyDogFarms]

I think the function of how much rainfall makes it into the tipper depends on placement of the rain gauge, diameter of the rain gauge funnel or "catch basin", and the height of the rain gauge walls and slope of the funnel.  The smaller diameter of the WH65 funnel means there is less potential surface area where rainfall would be "caught" and directed into the funnel, but that may be offset by higher walls or a steeper slope to the funnel that directs a higher proportion of the rainfall within that diameter to the tipping bucket (thus a more "efficient" funnel). 

The readings of the WH65 and the WH40 are likely factory calibrated to measure the rainfall in the particular area represented by the diameter of the funnel assuming 100% efficiency in directing the rainfall into the tipping bucket.  Whether or not a smaller diameter but more "efficient" funnel would provide better or worse accuracy in the WH40 would just take some comparisons between the readings of a WH40 with the WH65 funnel vs the measurement of that same rainfall in a Stratus rain gauge.

[K7RMK]

I just did a quick measurement of the top inner diameters.  I was using a tape measure so not exactly precise.

WH65=4 3/8"
Wh40= 7"

I'm getting 2.56 for gain.
(pi(7/2)²)/(pi(4.375/2)²)

[KD7GFL]

I will take your word for it lol


Hopefully somebody is able to test this.  As I said earlier, I am planning on returning my WH40 while I still can. Plus we don't have any rain forecasted anytime soon at my place.

[galfert]

K7RMK,
Before you return the WH40 can you measure the capacity of the tipping bucket? ..and compare that to the WH65? Just curious if they are different.

I agree with others that if you change the funnel diameter on the WH40 then you need to calibrate for the size difference. If you drive a snow plow you understand the difference the size of the shovel makes despite the distance traveled. The shovel is like your funnel.

[K7RMK]

K7RMK,
Before you return the WH40 can you measure the capacity of the tipping bucket? ..and compare that to the WH65? Just curious if they are different.

I agree with others that if you change the funnel diameter on the WH40 then you need to calibrate for the size difference. If you drive a snow plow you understand the difference the size of the shovel makes despite the distance traveled. The shovel is like your funnel.

I'm not returning mine. KD7GFL is the one who mentioned that.

[Rover1822]

Unfortunately, the only thing I think this thread will change, is there will be an uptick in Stratus rain gauge sales as people start to evaluate their systems. Probably not something Ecowitt or Ambient and of course Fine Offset foresaw . They more than likely expected people to blindly accept the given values.

I know because I just ordered a Stratus.

[galfert]

K7RMK,
Before you return the WH40 can you measure the capacity of the tipping bucket? ..and compare that to the WH65? Just curious if they are different.

I agree with others that if you change the funnel diameter on the WH40 then you need to calibrate for the size difference. If you drive a snow plow you understand the difference the size of the shovel makes despite the distance traveled. The shovel is like your funnel.

I'm not returning mine. KD7GFL is the one who mentioned that.

Oops...Yes, I confused usernames sorry.

[WXDA]

Is there any way to swap the two funnels and see if that makes a difference? May need to be bodged.

[CW2274]

I was contemplating switching to a Davis with a Rainwise 111.

Guarantee you'll never look back. I also have the Stratus directly next to the RW to back it up. Winning combo.

[KD7GFL]

K7RMK,
Before you return the WH40 can you measure the capacity of the tipping bucket? ..and compare that to the WH65? Just curious if they are different.

I agree with others that if you change the funnel diameter on the WH40 then you need to calibrate for the size difference. If you drive a snow plow you understand the difference the size of the shovel makes despite the distance traveled. The shovel is like your funnel.

I am not sure that I have what is needed to give you an accurate measurement of the capacity of the bucket, but if it helps, they appear to be the same internal parts for both.

WH65:

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WH40:

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[galfert]

KD7GFL,
Thank you that helps. I think that they are the same part from the looks of it. I think this begins to answer some questions. The larger funnel diameter means that the same size spoon is going to have a harder time keeping up with the bigger rain falls as it will need to tip much quicker. The increase in number of tips to record the same amount of rainfall results in a loss of accuracy. From an engineering perspective this makes total sense. What should have been done is to have provided an equally larger spoon to make up for the larger collection of water with the larger diameter funnel.

Because of this I think that a possible fix is to use the WH65 funnel on the WH40 and then just calculate what the adequate offset should be (2.56 thanks to K7RMK) for the reduced size diameter.

Yes I double checked the math on the offset.
Area of circle = (C²)/4pi

[olicat]

Hi!

Really a very interesting comparison.
I rotated the pictures a bit and placed them next to each other.
From the photos I would say they are the same parts!

Oliver

[K7RMK]

KD7GFL,
Thank you that helps. I think that they are the same part from the looks of it. I think this begins to answer some questions. The larger funnel diameter means that the same size spoon is going to have a harder time keeping up with the bigger rain falls as it will need to tip much quicker. The increase in number of tips to record the same amount of rainfall results in a loss of accuracy. From an engineering perspective this makes total sense. What should have been done is to have provided an equally larger spoon to make up for the larger collection of water with the larger diameter funnel.

Because of this I think that a possible fix is to use the WH65 funnel on the WH40 and then just calculate what the adequate offset should be for the reduced size diameter.

I agree, if the issue is due to the tipping spoon not being able to keep up during hard rain, then the smaller funnel and calibration should fix the issue. The downside is it's going to take almost 3 times as much rain for each reading which isn't as desirable for light rain. It would be nice to know if the tipping spoon is actually the problem.

[Rover1822]

OK, it's good to know the buckets are the same, do they have the same fill level before tipping, that would be the spring device. I'm going to assume they do, but that is an assumption.

As was just posted, the downside to shrinking the funnel and then augmenting the calibration is it will become less responsive to lower rain amounts, which is more than likely why the WH40 has a wider funnel.

All of this is assumption

... my thoughts, they need to figure this out and re-engineer it. Sure they don't want to do that, made molds, done production runs, right now it is what is. There is not a small cost to the manufacturer for a fix.

So ... keep up the opinions and point out the facts, as we are doing.

[cheffy]

Hi all,

My 1-wire rain guage died on me about 3 weeks ago and in a panick I quickly rushed out and bought the Ecowitt 1002.  A few days after I received it I found this thread - wished I found it earlier!  I must admit, when I first saw how shallow the funnel was I had concerns of rain bouncing out.

Anyway, since reading this thread I have been consistently comparing the guage to a manual rain guage which is set at the same height next to it.  My rain guage is set about 40cm from the ground.

The last couple of weeks have been pretty wet, with most days receiving some form of rainfall.  So far what I have found is the WH40 has been tracking pretty close to the manual guage, albeit in some cases slightly lower.  On the small amounts there is a slight difference, eg 1.8mm in the WH40 and 2mm in the manual guage - however it is hard to compare small amounts of rainfall so I generally not too concerned about that.  On the larger amounts, the WH40 has been the same as the manual guage, eg 5mm and 12.5mm.  The rainfall I have had has been slow intermitent, mixed in with some heavier downpours.  We haven't really had any torrential rain yet, but I guess time will tell when that happens.

I know its only been a few weeks, but at the moment it's been tracking reasonably well.

If in the event it does become inaccurate I was thinking of swapping the funnel over for a plastic funnel that has a much deeper fall.  I measured the diameter of the WH40 and it is 7".  You can buy a 7" plastic to funnel to replace it with.  Not sure if it will work and how it will sit, but has anybody thought of doing that?

Neil

[MacGarage]

Okay...I may throw a wrench into this...hope not!

My Ecowitt WH2320E has the smaller rain sensor...probably like the WH65.

It failed earlier and I had it replaced (quickly) by Ecowitt.

However, I noticed that it was not accurately measuring heavy rains earlier this summer. I attempted to calibrate it but it caused the lighter rain measurements to be off so I set it back to default. The readings were so much of a concern, I pulled it for my WU reporting and started to use my Atlas. My Ecowitt is fine during normal rains but still does not record the heavier rains.

Odd thing is that before the current sensor replacement, I felt the heavy rain measurements were okay. However, I may just not have noticed it.

I attached an image of the old sensor that I replaced.

Edit: I also noticed that the improper heavy rain reporting was mirrored with the console. Without the calibration in the GW1000, the totals matched.

[Platokidd]

Ahhh...I had missed that post, thanks!  I'm assuming that the diameter or protruding parts of the WH65 funnel and WH40 funnel are different so that one could not try the WH65 funnel on a WH40 and see how that effects accuracy.

I am not sure, but you may be on to something.  I just verified that the rain collector top for the WH65 will attach to the WH40. The lower dimensions of both tops are the same as far as connecting to the base.  [ You are not allowed to view attachments ]  

 The WH65 top may improve accuracy in comparison to the poor design of the factory WH40 top.

(EDIT:  After thinking about it, I don't think any adjustment to the Rain Gain would be necessary. )


I would try this, but I have uninstalled my WH40 and am awaiting guidance on how to return it for a refund.  Maybe somebody else has a WH65 top around that would be willing to test it.

I just happen to have a new extra wh65 funnel laying around and will give this a go. Will go back to the 1.0 offset default with the smaller funnel.
That said it's August and this is our dry season in Illinois.

I can always go back to the lager funnel and 1.4 offset that has seem to work well for me in light to heavy rains.

[Platokidd]

I just did a quick measurement of the top inner diameters.  I was using a tape measure so not exactly precise.

WH65=4 3/8"
Wh40= 7"

I'm getting 2.56 for gain.
(pi(7/2)²)/(pi(4.375/2)²)

Interesting. On the larger funnel Ive notice heavy rain bouncing off and out. Light rain beads up in the funnel and never passes.
.
Think the shallow outer angle of wh40 funnel is the issue and not so much the over all size.

Can you crunch the numbers to compensate for the angle differences in funnels?  I know I sure cant...

Or measure the wh40's steep center part diameter of the funnel only and re crunch the numbers.

[GHammer]

I wrote Ecowitt yesterday and here's what they say.

"Please don't worry and we're trying to find a solution to fix the WH40 issue now.
Could you please give us some time to do that?
Sorry for the inconvenience caused."

Seems encouraging coming from a company I trust.

[john21283]

Think the shallow outer angle of wh40 funnel is the issue and not so much the over all size.

WMO recommend a funnel angle greater than 45 degrees (from horizontal)

I wrote Ecowitt yesterday and here's what they say.

"Please don't worry and we're trying to find a solution to fix the WH40 issue now.
Could you please give us some time to do that?
Sorry for the inconvenience caused."

Seems encouraging coming from a company I trust.

I have been impressed by Ecowitt’s responses listed on this forum so i am guardedly optimistic that they will solve this problem. Fine Offset are the manufacturer, Ecowitt the retailer so i Expect  it will take some time to resolve.

[KD7GFL]

I was notified by Ecowitt that they will be providing a refund for my WH40 purchase, but due to the high cost of shipping to China  I will not be expected to return it. 

So I will be able to do some testing using the WH40 with the WH65 rain collector top and an adjusted Rain Gain of 2.56 and compare the results to a Stratus.  Unfortunately we are in a dry spell with no rain forecasted for the next week so it will be several days before this will occur.

[WXDA]

Unfortunately we are in a dry spell with no rain forecasted for the next week so it will be several days before this will occur.

You mean you’re not going to stand there with a hosepipe?

[Platokidd]

I just did a quick measurement of the top inner diameters.  I was using a tape measure so not exactly precise.

WH65=4 3/8"
Wh40= 7"

I'm getting 2.56 for gain.
(pi(7/2)²)/(pi(4.375/2)²)

Interesting. On the larger funnel Ive notice heavy rain bouncing off and out. Light rain beads up in the funnel and never passes.
.
Think the shallow outer angle of wh40 funnel is the issue and not so much the over all size.

Can you crunch the numbers to compensate for the angle differences in funnels?  I know I sure cant...

Or measure the wh40's steep center part diameter of the funnel only and re crunch the numbers.

Ok, i have switched out the funnel on the wh40 to use the wh65's funnel. Actually looks like the wh65 (4.5") has a larger funnel when you consider the shallower angled wh40 (3.5"").
The wh40 has about 3" of useless trampoline area around the outside of the funnel.
Reset my offset to 1.0 and will report back when we get some much needed rain.
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[Rover1822]

With the smaller funnel on the WH40, shouldn't you be bumping up your calibration to account for the difference in the diameters and surface areas, as opposed to backing it down to 1?. I believe this was previously discussed. Or did I miss something entirely?