Author Topic: WH40 0.5mm under compared to Davis  (Read 532 times)

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Offline Bashy

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WH40 0.5mm under compared to Davis
« on: May 12, 2022, 04:17:16 AM »
Had some rain yesterday, some light, medium and heavy, the latter was a minute or so.

The Davis recorded 6.2mm and the WH40 recorded 5.7mm

To be fair, i don't know what the accuracy is, so is this normal or acceptable for the WH40?
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Offline CW2274

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Re: WH40 0.5mm under compared to Davis
« Reply #1 on: May 12, 2022, 05:17:09 AM »
To be fair, i don't know what the accuracy is, so is this normal or acceptable for the WH40?
:?  How would you know? Has either gauge been truly calibrated? Without that, you're comparing one unknown against the other. Gotta have a control.

Offline Bashy

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Re: WH40 0.5mm under compared to Davis
« Reply #2 on: May 12, 2022, 05:23:59 AM »
My manual ties in quite nicely with the Davis.
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Offline CW2274

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Re: WH40 0.5mm under compared to Davis
« Reply #3 on: May 12, 2022, 05:35:59 AM »
My manual ties in quite nicely with the Davis.
Then I guess we carry on.  ;)

Offline Gyvate

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Re: WH40 0.5mm under compared to Davis
« Reply #4 on: May 12, 2022, 09:22:09 AM »
The WH40 is generally known for rather underreading and the WH65/WS69 rain bucket for overreading.
At low rain rates the WH40 comes close to the manual readings, but the stronger the rain gets, the more the underrreading (a systematic affair due to the funnel design).
But it depends a lot on the type of rain (drizzle, medium, strong, very strong ...) and the accompanying wind situation.
The same, by the way, for the WS90 haptic rain sensor.
While many report an overreading with the WS90, I could not confirm that in over 30 rain days - at two days it was overreading (reference two manual rain gauges) and otherwise generally underreading, and provided generally lower values than the WH40. (for the WS90 all five rain gains = 1.0) The usual observation of mine is WH65 > Manual > WH40 > WS90
Froggit WH4000SE (=EW 2320E) 1.6.4/GW1100 2.1.4/Froggit DP1500 1.6.8 (+EW GW1000 (4) 1.6.8/7.2 test/backup)/HP1000SE Pro (HP2551) 1.6.4/1.7.8, WH2650 WiFi (2) 1.7.2,GW2000 2.1.4;
Ecowitt WS90-,WS80,WH40,WH65,WH31(5),WH31-EP(1),WN30/DP30 (1),WH32(1),WH32-EP(1),WH32B [T/H/P] (1), WH57 [Lightning] (1), WH41 [PM2.5] (2), WH51 [SoilMoisture] (5), WH45, WH55 (2)
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Offline giusCB

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Re: WH40 0.5mm under compared to Davis
« Reply #5 on: May 12, 2022, 10:28:26 AM »
Had some rain yesterday, some light, medium and heavy, the latter was a minute or so.

The Davis recorded 6.2mm and the WH40 recorded 5.7mm

To be fair, i don't know what the accuracy is, so is this normal or acceptable for the WH40?

first to all, set the correct offset for the wh40 ( 1.022 ) and check if is on level

Offline Rover1822

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Re: WH40 0.5mm under compared to Davis
« Reply #6 on: May 12, 2022, 12:34:17 PM »
Gyvate, on the WS90, I'm having the same experience, I am finding that the WS90 seriously under reads with wind blown rain, rain at an angle. I've been having major winds here 25 MPH constant with gusts above that.

Ambient:WS-2000,PM 2.5 x2,WH31B x2,WH40E,WH31P
EcoWitt: GW1100,GW1000 x4,WH31 x2,WH57,WH51 x12, WH40,WH5360B,WN34S,WittBoy
Web Sites: WU, Ambient Weather , Ecowitt.net , Ecowitt.net (TEST)
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Offline Bashy

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Re: WH40 0.5mm under compared to Davis
« Reply #7 on: May 14, 2022, 03:32:55 AM »
Thanks guys and sorry for the late reply, re lower rain intensity, i certainly agree there, its pretty much neck and neck with the Davis and manual. Because my recent rain included various intensities and more so the heavy for around a minute is what caused the discrepancy seen i had my suspicions, i think its gets overwhelmed and perhaps been more suited to 0.2mm resolution? To be fair, i did have my reservations on the bucket size and on the cone size, i had a feeling it may see some performance related, I'm gonna say issues but that might be a bit ott...

Is the offset of 1.22 the done thing then? and it is 99.99% level, its only 2ft off the ground so very easy to see these things.

As a side note, i did add an old OS bucket debris shield, this lets in far less that the standard effort :)

Quote
The same, by the way, for the WS90 haptic rain sensor.
While many report an overreading with the WS90, I could not confirm that in over 30 rain days - at two days it was overreading (reference two manual rain gauges) and otherwise generally underreading, and provided generally lower values than the WH40. (for the WS90 all five rain gains = 1.0) The usual observation of mine is WH65 > Manual > WH40 > WS90

I would have expected differences with the haptic, still kicking myself for not checking to see if it was available lol
« Last Edit: May 14, 2022, 03:34:44 AM by Bashy »
Kind regards
Bashy

Offline Platokidd

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Re: WH40 0.5mm under compared to Davis
« Reply #8 on: May 14, 2022, 12:26:16 PM »
My wh40 is spot on with my Stratus.
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Ambient    
2- WS-2000 2-WS-2902A ARRAYS 1-CONSOLE 2-WH40-RAIN 1-WH31L 1-METEOBRIDGE 2-PM2.5
3-WH-31E 1-SRX100LX 1-WH31SM

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3-HP2552-WH51 9-WH31-2-WH45-1-WH55
2-GW1000 1-GW1100- 5-WH51 1-WH32EP

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Offline Rover1822

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Re: WH40 0.5mm under compared to Davis
« Reply #9 on: May 14, 2022, 12:35:58 PM »
When clean, so are mine  :grin:

Unfortunately, mine are also some kind of tree, seed, pollen bomb, debris magnet

Partly why I got the WS90
Ambient:WS-2000,PM 2.5 x2,WH31B x2,WH40E,WH31P
EcoWitt: GW1100,GW1000 x4,WH31 x2,WH57,WH51 x12, WH40,WH5360B,WN34S,WittBoy
Web Sites: WU, Ambient Weather , Ecowitt.net , Ecowitt.net (TEST)
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Offline Bashy

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Re: WH40 0.5mm under compared to Davis
« Reply #10 on: May 24, 2022, 11:56:12 AM »
I cant take the WH40 seriously anymore, not in heavy rain anyway,

Davis  180mm/hr 4mm
WH40 18mm/hr 3mm
WH40 lost 1mm in a 4mm event, the event lasted 5mins max
« Last Edit: May 24, 2022, 11:59:34 AM by Bashy »
Kind regards
Bashy

Offline Gyvate

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Re: WH40 0.5mm under compared to Davis
« Reply #11 on: May 24, 2022, 04:02:38 PM »
the WH40 is since long known for underreading in strong rains.
Due to the poor design of the funnel (too flat, too low edge) a lot of rain gets lost splashing off.
Froggit WH4000SE (=EW 2320E) 1.6.4/GW1100 2.1.4/Froggit DP1500 1.6.8 (+EW GW1000 (4) 1.6.8/7.2 test/backup)/HP1000SE Pro (HP2551) 1.6.4/1.7.8, WH2650 WiFi (2) 1.7.2,GW2000 2.1.4;
Ecowitt WS90-,WS80,WH40,WH65,WH31(5),WH31-EP(1),WN30/DP30 (1),WH32(1),WH32-EP(1),WH32B [T/H/P] (1), WH57 [Lightning] (1), WH41 [PM2.5] (2), WH51 [SoilMoisture] (5), WH45, WH55 (2)
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Offline horseflesh

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Re: WH40 0.5mm under compared to Davis
« Reply #12 on: May 25, 2022, 12:18:33 PM »
Why is the WH40 offset 1.022? I don't even see where to set that in the calibration controls.

At what rate does the WH40 start to fail? Where I live, 1 inch/hr is pretty heavy rain. Even 1.5 in/hr would look Biblical, haha.

Offline Rover1822

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Re: WH40 0.5mm under compared to Davis
« Reply #13 on: May 25, 2022, 12:42:32 PM »
Why is the WH40 offset 1.022? I don't even see where to set that in the calibration controls.

At what rate does the WH40 start to fail? Where I live, 1 inch/hr is pretty heavy rain. Even 1.5 in/hr would look Biblical, haha.

In VSView +, look under more/rain totals, not under more/calibration.
FYI, I don't use the offset as 99% of the time it  is within a few percentage points of my manual rain gauge, plus or minus (within the published error for the device). As using an offset (rain gain) for the WH40 means for all rain rates, I rather not use it.
Ambient:WS-2000,PM 2.5 x2,WH31B x2,WH40E,WH31P
EcoWitt: GW1100,GW1000 x4,WH31 x2,WH57,WH51 x12, WH40,WH5360B,WN34S,WittBoy
Web Sites: WU, Ambient Weather , Ecowitt.net , Ecowitt.net (TEST)
Personal Sites: Weather Cam

Offline DelChard

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Re: WH40 0.5mm under compared to Davis
« Reply #14 on: May 26, 2022, 05:58:23 AM »
Why is the WH40 offset 1.022? I don't even see where to set that in the calibration controls.

At what rate does the WH40 start to fail? Where I live, 1 inch/hr is pretty heavy rain. Even 1.5 in/hr would look Biblical, haha.

In VSView +, look under more/rain totals, not under more/calibration.
FYI, I don't use the offset as 99% of the time it  is within a few percentage points of my manual rain gauge, plus or minus (within the published error for the device). As using an offset (rain gain) for the WH40 means for all rain rates, I rather not use it.
Another reason for not using is contained in post https://www.wxforum.net/index.php?topic=39166.
The post requires reading in its entirety, as there is a lot of confusion in the early stages.
My memory is that Ecowitt have attempted to correct the error within the gateway or console firmware.
However, the respective firmwares have all changed in the mean time?????

Re Bashy's issue. I also had an 18mm/hr event about 30 mins earlier.
My WS69 (which reportedly over reads) recorded 18.6mm/hr and 3.3mm total. My WH40 recorded 18mm/hr and 3.1mm total.
Both are within 10 feet of each other and 8 feet high (necessary to keep the canines from triggering a rain event)
A nearby (1/2 mile) davis station recorded less. (for what thats worth).
GW1100 - WS80 WH40 WH32EP
Feeding Weewx on Pi4b, CumulusMX on Synology DS215+

GW1100 - WS69
HP2550 - WS80 WH40

Extras common to all 3
WH51 5, WH31 4, WN30 3, WH57, WH41 1, WN34S 1, WN35 1, WH55 1

 

anything