Topic: WH40 vs WH65 Rain Measurements

[havtrail]

I'm no PWS expert, but from looking at photos on this forum, I wonder how many of them actually would meet the requirements shown on the drawings you provided. Most of them look like small, shallow birdbaths to me. However, I have an unusual perspective, since I volunteer to keep our township's HOBO weather station going, and its rain gauge is 6" in diameter and 9" deep.

I'd like to see people here with various PWS brands check their rain gauge against the drawings you provided and see how many inches (or mm) they are short of meeting it. It would seem that simple but accurately sized cylindrical collars could be made and affixed to lower-cost stations, to improve their retention of bouncing raindrops and therefore their accuracy.

Rich K.

[KD7GFL]

The answer I received from Lucy in an email this morning is that Ecowitt is not planning on modifying the WH40 rain collector top.   Their stand is increasing the height of the side walls will not improve accuracy.  She did not provide any other suggestions are options to resolve the issue. I have requested to return my WH40 for a full refund since it has proven to be highly inaccurate when compared to a Stratus rain gauge and Ecowitt apparently has no way to correct it.

I do not believe adjusting the Rain Gain is an efficient way to resolve the inaccuracy.  I verified that my sensor is properly calibrated according to Ecowitt's recommendation (manually activating the tipper 10 times should provide a reading of 1.0 mm/.04 inches.)  I believe increasing the gain to adjust for under-reporting during heavy/intense rain will result in over-reporting of rain accumulation during periods of light or moderate rain.

At least for now I am going to reinstall an extra 2902/WH65 which my current sensors had replaced and compare that to the Stratus.  Are there any other options that are compatible with a GW1000? 

[galfert]

I think the WH65 is the best solution. There is nothing else that will work.

[Rover1822]

Has anyone tried to increase the height of the walls with maybe a band of plastic? Maybe attached with a large hose clamp, with a bead of silicone caulk on the inside where it meets the funnel.

Just musing

[galfert]

Someone should design a new funnel and throw it on Thingiverse.

[KD7GFL]

I did a quick check on Amazon reviews and others figured out the WH40 was not accurate a long time ago.   My guess is most of the positive reviews are by people who never verified the accuracy against a quality rain gauge.   

I figure if Ecowitt/Fine Offset isn't willing to try to make it accurate, I am not going to waste my time and money to make it work.

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[Rover1822]

I was thinking more of those that already have one . I would not buy one just to modify it

[Platokidd]

I did a quick check on Amazon reviews and others figured out the WH40 was not accurate a long time ago.   My guess is most of the positive reviews are by people who never verified the accuracy against a quality rain gauge.   

I figure if Ecowitt/Fine Offset isn't willing to try to make it accurate, I am not going to waste my time and money to make it work.

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I adjusted the offset of the wh40 to 1.42 . It now reads within .01" when compared to the wh65 (ws-2902a) that is also spot on to my manual rain gauge. I do not recommend the wh40.

[galfert]

Is there really an offset calibration that could work for everyone? Or is it not the likelihood that for each type of rainfall (sprinkling or hard downpour) that a different calibration offset would be required?

I believe that there is no true way to calibrate for all types of rainfall. If you found an offset that works for you maybe it is because you only see one type of rainfall, and that one day that is different will result in poor performance.

[LazyDogFarms]

For those who have both the WH40 and the Osprey array, what is the difference between the two funnels?

From looking at photos of the Osprey array, that funnel appears the same as the funnel on my WH40,  but I am assuming that there must be variations, such as diameter, wall height or slope angle.

[galfert]

The diameter of the WH40 is much greater than the WH65. You can see the size difference in this earlier post by KD7GFL:
https://www.wxforum.net/index.php?topic=39166.msg412522#msg412522

Although the WH40 is marketed as being superior and that is because of the larger diameter, it actually performs worse I think because of the slope difference. The slope of the WH40 is too flat...almost horizontal causing I'm sure much rain to bounce out. Both the WH40 and the WH65 have short walls so they probably both present a problem with rain catch if it is windy, but again the slope on the WH40 probably makes it worse.

It also might be a function of the tipping cup in that they may be exactly the same size buckets (cup size). Therefore because of the larger diameter the WH40 is collecting more total amount of rain. Each one would be calibrated to its capture diameter, but if they are the same size catching cup/bucket then the WH40 is going to by nature have a harder time keeping up with high rainfall amounts as there may be more spillover or loss and perhaps it just can't keep up. But this is just a guess as I don't have the WH40 to be able to compare cup/bucket size.

[LazyDogFarms]

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.

[funsutton]

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.

Even if that worked, it would effectively become a WH65 and one might as well stick with the osprey.

[GHammer]

Rainfall is the primary reason for my PWS. I use it to feed my irrigation system data for just the right amount of watering.
I sold my old WH65 in order to have separate sensors.
This was billed as more accurate, but has turned out to be worse.
At the time, I was contemplating switching to a Davis with a Rainwise 111.
I'm surprised that Ecowitt has allowed this to stand. I've written them and gotten reply saying that they are aware of the issue, have tested different versions and decided the current version is the best one. If it is a matter of the height, then I can't understand why a new funnel is not forthcoming.

Look, I'm not asking for a freebie, I'd pay for a new funnel.

This is unacceptable to me. In a couple of months, I'll put my equipment up for sale and proceed with the Davis plan.

[KD7GFL]

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.

[LazyDogFarms]

The WH65 funnel is $11.49 on Ambient Weather (https://www.ambientweather.com/amws2902funnel.html).  Perhaps I'll order one for my WH40 just to run some comparisons and see how it changes accuracy. 

[Rover1822]

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

Maybe I'm missing something, but the WH40 has a larger surface area than the WH65. So I can't see how a re-calibration would not be necessary for the conversion from volume to a linear measurement such as mm or inches of rain which would require in calculation the volume over surface area.

And I don't know if the bucket sizes are the same, but even if they were , still see a calibration needed if switched.

[KD7GFL]

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

Maybe I'm missing something, but the WH40 has a larger surface area than the WH65. So I can't see how a re-calibration would not be necessary for the conversion from volume to a linear measurement such as mm or inches of rain which would require in calculation the volume over surface area.

And I don't know if the bucket sizes are the same, but even if they were , still see a calibration needed if switched.

I initially looked at it as you did, but the funnel is just an avenue for the water the enter the tipper.  The tipper mechanism is what is calibrated.  While the funnel may change the rate of water entering the tipper, when the tipper is full it will activate and register the calibrated amount.  If you manually activate the tipper on the WH40 it will register .1 mm each and every time (if functioning properly.)  If I were to pour 2.0 mm of water into the WH40, regardless of what top it has, it should accurately register 2.0 mm of rain.

In other words, by changing the funnel you would not change the amount of rain required for the tipper to activate so I don't believe changing the funnel will affect calibration.  I believe the WH65 funnel will however affect the actual percentage of rain that makes it to the tipper.

[Rover1822]

The tipper measurement is based on weight , and knowing the value for the density of water , is then used to generate a volume of water that caused the tip. Once the volume of water is known, then that can be used to calculate how much volume fell over a surface area. From that you can calculate the depth of the water for that surface area, which gives you the linear measurement of mm or inches of rain. You need to know the surface that the rain fell on, which makes changes in the diameter of the funnel important.

So the tipper tips on a weight which equals a volume. It does not tip on the linear measurement.

Anyone feel free to correct me. Been a long morning.

[K7RMK]

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

Maybe I'm missing something, but the WH40 has a larger surface area than the WH65. So I can't see how a re-calibration would not be necessary for the conversion from volume to a linear measurement such as mm or inches of rain which would require in calculation the volume over surface area.

And I don't know if the bucket sizes are the same, but even if they were , still see a calibration needed if switched.

I initially looked at it as you did, but the funnel is just an avenue for the water the enter the tipper.  The tipper mechanism is what is calibrated.  While the funnel may change the rate of water entering the tipper, when the tipper is full it will activate and register the calibrated amount.  If you manually activate the tipper on the WH40 it will register .1 mm each and every time (if functioning properly.)  If I were to pour 2.0 mm of water into the WH40 regardless of what top it has, it should accurately register 2.0 mm of rain.

In other words, by changing the funnel you would not change the amount of rain required for the tipper to activate so I don't believe changing the funnel will affect calibration.  I believe the WH65 funnel will however affect the actual percentage of rain that makes it to the tipper.

Changing the diameter of the funnel will make it catch a different amount of rain but yet it's going into the same tipping bucket size. Therefore, without calibration, it will be off. That's the easiest way to look at it. The only time changing the diameter of the funnel doesn't affect the reading is when the catch basin size follows the funnel diameter (like on a manual gauge). You need to take the area of the WH65 funnel and divide it into the area of the WH40 funnel. This will be the gain to use. I don't know the diameter of each funnel, but if the WH40 is 4" and the WH65 is 2.5", the gain would be 2.56. Does the GW1000 allow a gain this high? That's another question.

[KD7GFL]

Looks like I am mistaken, not really my lane, but here is what is confusing me:

Are you saying that if I pour 2.0 mm of water into the WH40 with the WH65 top it will register a different amount than if I pour 2.0 mm of water into it with the original WH40 top? (With the same Rain Gain setting.)

[K7RMK]

Maybe I am wrong, not really my lane, but here is what is confusing me:

Are you saying that if I pour 2.0 mm of water into the WH40 with the WH65 top it will register a different amount than if I pour 2.0 mm of water into it with the original WH40 top?

2mm is not a unit of water. What volume? 2mm from the same cup? Then that's a specific volume. The funnels do not collect the same volume when it's raining. The larger one collects more because it is larger.

I should clarify 2mm can be a unit of rainfall, but not water. You can't pour 2mm of water into the gauge unless the cup you are pouring from and measuring from is the same diameter as the funnel you are pouring into. You will be pouring more water with the larger cup.

[KD7GFL]

I think I understand the error in my thinking now.

[K7RMK]

I think I understand the error in my thinking now.

And yes to answer your earlier question, you can adjust the rain gain in the GW1000 calibration menu.

Does it have a calibration limit? If it doesn't allow values over 1.5 or something, then this isn't going to work.

[KD7GFL]

I plugged in 3.0 and was able to successfully save that amount.