Author Topic: Rain Gauge Issues with new VP2  (Read 1182 times)

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Offline Padnandos

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Rain Gauge Issues with new VP2
« on: April 10, 2021, 02:50:55 PM »
i recently upgraded my Vue to a VP2 a few weeks ago.

What i have noticed is that the rainfall everyday is off compared to my old vue. Even though i have the Vue and VP2 side by side and at the same height. The New VP2 under reads by as much as 2mm.

Its extremely frustrating especially with a new vp2.

Now ill say this but i dont know if it makes any difference, my old vue is an american model so its calibrated in factory to 0.01" with every tip whereas the vp2 is calibrated to 0.2mm(UK Model).

I have made sure there is no more potential issues that could be causing this. Any help would be appreciated.

Offline mikemaps

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Re: Rain Gauge Issues with new VP2
« Reply #1 on: April 10, 2021, 03:50:22 PM »
You need a manual rain gauge near the Vantage's to see which one is closer to being correct. Can't go by just 1 or 2 lighter rains & don't forget the specs say they are accurate to something like 5%, not perfect.

Offline Mattk

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Re: Rain Gauge Issues with new VP2
« Reply #2 on: April 10, 2021, 05:43:54 PM »
2mm by itself isn't any real indication. Even if both gauges were calibrated 2mm is still possible and acceptable depending on rain rate compared to the different gauges. As for factory calibration don't read too much in that, calibration is something a little different relative to the imperial or metric counter weights that can be fitted. The other thing is how do you know which is actually off (if any), all things being equal I would take the VP2 over the Vue   

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #3 on: April 10, 2021, 05:47:40 PM »
2mm by itself isn't any real indication. Even if both gauges were calibrated 2mm is still possible and acceptable depending on rain rate compared to the different gauges. As for factory calibration don't read too much in that, calibration is something a little different relative to the imperial or metric counter weights that can be fitted. The other thing is how do you know which is actually off (if any), all things being equal I would take the VP2 over the Vue   

Well just looking at surrounding stations, they seem to be closer to my old Vue. I know I shouldnít go by nearby stations, but they are pretty close within 3km.

I would stress that the VP2 is roughly 2.5 metres off the ground, but itís the best I can do with my garden due to buildings. But the Vue is literally the same height and right beside the VP2.

Today for example I had a light shower.
My old Vue recorded 0.2mm
The new VP2 recording 0.0mm

When I took off the rain cone of the VP2 and I found that the tipping spoon was nearly full of water but obviously not enough to tip the spoon.
« Last Edit: April 10, 2021, 05:56:26 PM by Padnandos »

Offline Mattk

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Re: Rain Gauge Issues with new VP2
« Reply #4 on: April 10, 2021, 06:00:08 PM »
Correct, don't get worried regard any surrounding stations, they really don't mean anything in any of this.

So at this point a figure of 2mm was mentioned, 2mm in how what rain total? Unless both the Vue and VP2 have been calibrated then everything is rather meaningless. As mentioned there will typically be a difference between totals even if calibrated and variable depending on rain rates     

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #5 on: April 10, 2021, 06:02:35 PM »
Well the figure of 2mm would usually come in when 5mm has been exceeded in a day usually. The rain rates are usually roughly the same give or take 1mm/hr

Example

The old Vue daily total of 7mm
The new VP2 daily total of 5mm

But not all the time

I havenít calibrated them in anyway :)

Offline Mattk

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Re: Rain Gauge Issues with new VP2
« Reply #6 on: April 10, 2021, 06:04:48 PM »
.......Today for example I had a light shower.
My old Vue recorded 0.2mm
The new VP2 recording 0.0mm

When I took off the rain cone of the VP2 and I found that the tipping spoon was nearly full of water but obviously not enough to tip the spoon.

I wouldn't be worried based on that, the two will never compare perfectly, who knows without being calibrated that the Vue may be over reading?

Edit: Rain rates will affect tipping gauges in different ways so the difference will not always be the same
« Last Edit: April 10, 2021, 06:07:45 PM by Mattk »

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #7 on: April 10, 2021, 06:07:34 PM »
.......Today for example I had a light shower.
My old Vue recorded 0.2mm
The new VP2 recording 0.0mm

When I took off the rain cone of the VP2 and I found that the tipping spoon was nearly full of water but obviously not enough to tip the spoon.

I wouldn't be worried based on that, the two will never compare perfectly, who knows without being calibrated that the Vue may be over reading?

Ofcourse yes thatís another way of looking at it. The Vue is 11 years old this year. But as I said the Vue is usually closest to the stations around me.

The ground would be beginning to get wet and the Vue would record the first 0.2mm tip, while it would take longer for the VP2 to record the first 0.2mm tip.

Offline CW2274

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Re: Rain Gauge Issues with new VP2
« Reply #8 on: April 10, 2021, 06:21:45 PM »
The only way you'll truly get a working knowledge is to calibrate them yourself or get one of these for comparison. Just using the Vue and VP2 against each other without a control is pretty meaningless.

https://www.scientificsales.com/6330-Stratus-Rain-Gauge-p/6330.htm

Offline ocala

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Re: Rain Gauge Issues with new VP2
« Reply #9 on: April 11, 2021, 05:35:58 AM »
The only way you'll truly get a working knowledge is to calibrate them yourself or get one of these for comparison. Just using the Vue and VP2 against each other without a control is pretty meaningless.

https://www.scientificsales.com/6330-Stratus-Rain-Gauge-p/6330.htm
Do this ^^^^
And don't worry about other stations. You are getting data from your backyard, not somebody else's.

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #10 on: April 11, 2021, 06:27:18 AM »
The only way you'll truly get a working knowledge is to calibrate them yourself or get one of these for comparison. Just using the Vue and VP2 against each other without a control is pretty meaningless.

https://www.scientificsales.com/6330-Stratus-Rain-Gauge-p/6330.htm
Do this ^^^^
And don't worry about other stations. You are getting data from your backyard, not somebody else's.

I know yes but the difference between my Old Vue and the New VP2 is bothering me

Offline ocala

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Re: Rain Gauge Issues with new VP2
« Reply #11 on: April 11, 2021, 09:33:25 AM »
To put your mind at ease put a know amount of water in each rain gauge on a slow drip and see what the results are. That should tell you what gauge is more accurate. To further calibrate do each on moderate drip and a fast drip. 

Offline CW2274

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Re: Rain Gauge Issues with new VP2
« Reply #12 on: April 11, 2021, 04:16:54 PM »
The only way you'll truly get a working knowledge is to calibrate them yourself or get one of these for comparison. Just using the Vue and VP2 against each other without a control is pretty meaningless.

https://www.scientificsales.com/6330-Stratus-Rain-Gauge-p/6330.htm
Do this ^^^^
And don't worry about other stations. You are getting data from your backyard, not somebody else's.

I know yes but the difference between my Old Vue and the New VP2 is bothering me
I say again, you'll never know which if either is accurate as it can be until you have something of know value to compare to. Simple as that.

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #13 on: April 11, 2021, 04:19:54 PM »
The only way you'll truly get a working knowledge is to calibrate them yourself or get one of these for comparison. Just using the Vue and VP2 against each other without a control is pretty meaningless.

https://www.scientificsales.com/6330-Stratus-Rain-Gauge-p/6330.htm
Do this ^^^^
And don't worry about other stations. You are getting data from your backyard, not somebody else's.

I know yes but the difference between my Old Vue and the New VP2 is bothering me
I say again, you'll never know which if either is accurate as it can be until you have something of know value to compare to. Simple as that.

Many thanks for your advice. Iíve actually noticed today that each new VP2 tip of 0.2mm was worth 2 tips of the old Vue. So therefore 0.6mm was the total for the new VP2 and 1.2mm for the old Vue.

Could be just a coincidence though but I will keep note of a potential pattern.

Offline CW2274

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Re: Rain Gauge Issues with new VP2
« Reply #14 on: April 11, 2021, 04:21:05 PM »
To put your mind at ease put a know amount of water in each rain gauge on a slow drip and see what the results are.
This won't work due to the different values of water needed for the two different ISS's. For instance, the VP2 (at least the old spoon design) takes 544ml of water to equal one inch of rain. I have no idea what the Vue is, but I'm all but certain they would be considerably different.

Offline PaulMy

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Re: Rain Gauge Issues with new VP2
« Reply #15 on: April 11, 2021, 05:10:22 PM »
Are you sure the hardware (ISS) is correct for mm (0.2 mm per tip), and the consoles' settings to match?


Enjoy,
Paul

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #16 on: April 11, 2021, 05:12:42 PM »
Are you sure the hardware (ISS) is correct for mm (0.2 mm per tip), and the consoles' settings to match?

For the new VP2? Yup they are both at 0.2mm.

My old Vue is American. Would that have any effect on the difference?
« Last Edit: April 11, 2021, 09:07:00 PM by galfert »

Offline PaulMy

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Re: Rain Gauge Issues with new VP2
« Reply #17 on: April 11, 2021, 07:11:21 PM »

Quote
My old Vue is American. Would that have any effect on the difference?
There should be no significant difference whether they are inch or mm, as long as the ISS and the console setting are matched.
My first VP2 was bought in Canada and came with the mm sleeve installed in the ISS.
My replacement ISS 10 years later from USA vendor came with a separate sleeve for mm that I had to install.


Enjoy,
Paul

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #18 on: April 12, 2021, 03:13:51 AM »
How do you set the ISS to mm or inches?

I have the console set to 0.2mm

Offline Mattk

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Re: Rain Gauge Issues with new VP2
« Reply #19 on: April 12, 2021, 05:55:16 AM »
How do you set the ISS to mm or inches?

I have the console set to 0.2mm

The VUE can have an Imperial or Metric module, do you know which one your have? The VP2 rain collector can have an Imperial or metric counter weight, which one do you have?

When you know how the rain collectors are configured then the console can be set to display the required output   

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #20 on: April 12, 2021, 08:08:58 AM »
The VP2 is a UK Model.

The Vue is a US Model with I presume a metric collector 0.2mm

I feel like Iím at the conclusion that the VP2 tips less often then a Vue.
« Last Edit: April 12, 2021, 08:12:08 AM by Padnandos »

Offline azchrisf

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Re: Rain Gauge Issues with new VP2
« Reply #21 on: April 12, 2021, 12:15:38 PM »
You can call Davis OR your local supplier since you seem to be in the U.K. and explain you feel itís off.They will probably do an RMA and test it.

If the Vue was a US model it would be 0.01 inch per tip unless specifically ordered with the mm module - if that is even n option for Vues.

Do you have the tipping bucket or tipping spoon in your VP2?
Davis Vantage Pro 2 Plus 6163 w/ 8 Transmitters!
Also doing Soil and Leaf 4x
WU: KAZGLEND106 CWOP: FW1398 (F1398) Purpleair: 98793/LAZGLEND8

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #22 on: April 12, 2021, 12:19:19 PM »
Well ya see I had the same problem with the first new VP2 I got about a a month ago. My supplier then replaced it with another new VP2 a few days ago and Iím still having the same differences with my old Vue.

So thereís nothing wrong or faulty with this new VP2

If my Vue is at 0.01Ē module would that mean itís recording it as 0.25mm on the console?

Yea I have the tipping spoon in the VP2. I must actually double check what module is int the Vue, I have it 11 years and Iíve never checked it!

Offline azchrisf

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Re: Rain Gauge Issues with new VP2
« Reply #23 on: April 12, 2021, 02:27:05 PM »
If both are tipping spoons and 0.02mm, then I'd say yeah, reasonable deduction says you have something wrong.
Simply swapping one for another isn't a solution, the tipping spoon mechanism itself needs to be sent off for calibration. There is an adjustment screw for it, but it is not recommended users do it vs. the tipping bucket because it is non-linear.

The other route you can take is to downgrade/swap from the tipping spoon to the tipping bucket by buying a spare part and doing the swap (https://weatherspares.co.uk/products/davis-vantage-pro2-metric-rain-tipping-bucket-assembly-7345-444?_pos=6&_sid=0df589f48&_ss=r). They are both reed switches so they will work without any further modification. Some users like the tipping bucket's accuracy more. Personally my tipping spoon upgrade matches within 0.01 of my CoCoRahs rain gauge. I was having the same issues as you just backwards lol.

Whichever way you go, you will need to take time to calibrate it yourself to be correct, or send it off to Davis. There is no simple fix in this situation.
« Last Edit: April 12, 2021, 02:28:57 PM by azchrisf »
Davis Vantage Pro 2 Plus 6163 w/ 8 Transmitters!
Also doing Soil and Leaf 4x
WU: KAZGLEND106 CWOP: FW1398 (F1398) Purpleair: 98793/LAZGLEND8

Offline Padnandos

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Re: Rain Gauge Issues with new VP2
« Reply #24 on: April 12, 2021, 02:29:18 PM »
Thanks for the advice but this my second VP2 in the space of a month. Whatís the odds of the two of them being wrong?

Unless Ofcourse my old Vue is just over reading in general.