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Vangage Pro II Reed Switch Install

Discussion specific to Davis weather stations
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KC0WNY
Posts: 23
Joined: Wed 14 Nov 2012 7:03 am
Weather Station: Davis Vantage Pro II
Operating System: Windows 8 Pro
Location: United States

Vangage Pro II Reed Switch Install

Post by KC0WNY »

Is their a top or bottom on the reed switch, or any special installation tricks, I just installed one and it does not appear to be counting as it should. I tried not to touch the switch it's self. I measured out .50 in of water in a rain gauge tube and poured it in the collector, it only registered .17 in of rain, which is some improvement I guess, It wasn't counting anything before.
Amateur Radio Operators:
KC0WNY and KD0ACN Ted and Kay
BCJKiwi
Posts: 1255
Joined: Mon 09 Jul 2012 8:40 pm
Weather Station: Davis VP2 Cabled
Operating System: Windows 10 Pro
Location: Auckland, New Zealand
Contact:

Re: Vangage Pro II Reed Switch Install

Post by BCJKiwi »

Did you allow for any difference in areas of the rain gauge tube and Davis rain collector?
KC0WNY
Posts: 23
Joined: Wed 14 Nov 2012 7:03 am
Weather Station: Davis Vantage Pro II
Operating System: Windows 8 Pro
Location: United States

Re: Vangage Pro II Reed Switch Install

Post by KC0WNY »

No I did not, I would not know how to do that, I guess I assumed .50 in of water is .50 in of water no matter how it is measured.
Amateur Radio Operators:
KC0WNY and KD0ACN Ted and Kay
duke

Re: Vangage Pro II Reed Switch Install

Post by duke »

.50 of water is .50 of water but how are you trying to measure / calibrate? If they were both outside next to each other and the Davis is calibrated correctly they 'should' measure the same. Is the reed switch opening/closing with every pass of the bucket? You can check this by using a DVM or simply look at the console.

Here's a link to reed switch replacements and here is a link to calibration.
BCJKiwi
Posts: 1255
Joined: Mon 09 Jul 2012 8:40 pm
Weather Station: Davis VP2 Cabled
Operating System: Windows 10 Pro
Location: Auckland, New Zealand
Contact:

Re: Vangage Pro II Reed Switch Install

Post by BCJKiwi »

Not quite.
Some math required!

If the measuring cylinder had an opening of 1 square inch in area and 0.5 inches of rain fell then you would see 0.5 inches in the gauge.
If you then took another graduated measuring cylinder of 2 square inches in area and poured the water from the first cylinder into the second, it would show 0.25 inches of rain.
Visualise a small saucepan and a large saucepan on the lawn when it rains - they will both fill up to the same depth but the larger one will contain more water by volume.

So you have three options;
1. Wait until it rains and compare the VP2 to others nearby and if it is reasonably similar you are good to go.

2. Find a can with a similar diameter to the VP2 and fill it to a known depth and then measure that volume of water in your measuring cylinder, then drip it very slowly into the VP2 and see if you get the same amount. This is not easy to do as there is a maximum rate which is easy to exceed in which case some rain 'tips' are missed and will not show up on the console.

3. calculate and measure.
The formula for area is 3.1416 * radius * radius
Calculate the area for both the cylinder and the VP2.
Divide the VP2 area by the cylinder area.
If the answer is say 2.0, then the VP2 will indicate half the volume of water showing in the measuring cylinder.
Again if you try this method, drip the water in very slowly!
duke

Re: Vangage Pro II Reed Switch Install

Post by duke »

BCJKiwi wrote:Not quite.
Some math required!

If the measuring cylinder had an opening of 1 square inch in area and 0.5 inches of rain fell then you would see 0.5 inches in the gauge.
If you then took another graduated measuring cylinder of 2 square inches in area and poured the water from the first cylinder into the second, it would show 0.25 inches of rain.
Visualise a small saucepan and a large saucepan on the lawn when it rains - they will both fill up to the same depth but the larger one will contain more water by volume.
Good point - in my defence, it's still rather early here ;)
BCJKiwi
Posts: 1255
Joined: Mon 09 Jul 2012 8:40 pm
Weather Station: Davis VP2 Cabled
Operating System: Windows 10 Pro
Location: Auckland, New Zealand
Contact:

Re: Vangage Pro II Reed Switch Install

Post by BCJKiwi »

The VP2 rain bucket is approx. 16.4cm diameter (have not measured one myself).
If no tips were missed when the 0.5" rain was poured from the cylinder into the VP2 and the VP2 measured 0.17", then working backward, if the measuring cylinder is approx. 9.56cm diameter then the VP2 is reading the right amount.
KC0WNY
Posts: 23
Joined: Wed 14 Nov 2012 7:03 am
Weather Station: Davis Vantage Pro II
Operating System: Windows 8 Pro
Location: United States

Re: Vangage Pro II Reed Switch Install

Post by KC0WNY »

Well, I did check the tipping bucket manually by flipping it by hand slowly, it did count 0.01 with each tip, so, I guess I can assume it is counting correctly. Instructions to calibrate state: To check the accuracy of the rain collector, compare the Davis Rain Collector with a tube type rain gauge. Use a rain gauge with an aperture of at least 4 inches. Any smaller and the readings obtained may not be accurate. Place the tube type rain gauge directly next to the Davis rain collector. Compare the totals on three storms. So I guess I will check it against my National Weather Service approved rain guage I have. All I have to do is wait for it to rain, which we haven't had much of this year in SE Kansas. Thanks everyone for the Replies, It is appreciated.
Amateur Radio Operators:
KC0WNY and KD0ACN Ted and Kay
dvautier
Posts: 1
Joined: Wed 05 Apr 2017 6:42 pm
Weather Station: davis pro2
Operating System: win7

Re: Vangage Pro II Reed Switch Install

Post by dvautier »

Those reed switches seem to work in any direction. They just have to be in a magnetic field to close. Each time they close the unit measures .01 inch. I did a calibration this way. http://www.dvautier.com/misc/davis.htm 8-) 8-)
Red Raspberry
Posts: 23
Joined: Fri 07 Mar 2014 7:05 pm
Weather Station: Davis Vantage Pro 2
Operating System: Windows 7 Pro 64 bit
Location: Ashkum, Illinois

Re: Vangage Pro II Reed Switch Install

Post by Red Raspberry »

With my CoCoRaHS rain gauge 202 grams equals one inch of rain. It has a 4" opening and that is how I measure the water content of snow.

And the reed switch is just a magnet that acts on a steel contact. Polarity or direction make no difference.
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