Davis VP2 - add ons

[steve]

If anyone knows the volume of H2O Davis uses to callibrate say 1 inch of rain then please let me know

You can work it out. You said the diameter is 8.25 in, so the volume of water required for 1 inch of rain is 53.456 cu in.

[hailstone]

Good on you Steve, that is what I reqired. Maths are not my strong point as you can tell. Still I am a 68 year old pensioner.
Hailstone.

[hailstone]

Check my calculation please Steve before I set to and test the rain gauge.
I work that out at 8.76 litres.
I am pleased the collector in not any bigger otherwise it would cause a local hose pipe ban.
Hailstone.

[steve]

An order of magnitude out, I think it's 0.876 litres.

Don't forget to pour it very slowly.

[skyewright]

Check my calculation

You have the answer from Steve, but you might like to know that Google has a handy calculator for this sort of thing.

If you type 53.456 cu in in l into a google search you'll get the answer 0.875986893 litres.

It works for all sorts of units, with the general form <value> <unit> in <unit>

[hailstone]

So there you go. I said at the start I was a man of my word, and my statement about being poor at maths proves it. I did the calculation on a 24 year old Texas Instruments pocket calculator and managed to shunt the decimal point one place to the right. I have a Cola tin with a 1/2 mm hole drilled in the bottom. I use this patent method to calibrate the La Crosse gear.
That was a handytip about the Google calculator also, many thanks to all who have been my oracle over this poser.
Now I will have to wait for a long dry day to test the hardware and see if the software comes up trumps.
Let nothing you dismay.
Hailstone

[hailstone]

Dear o dear, there is what you might call an accumulation of fluctuations.
I took the collector measurements from the Davis catalogue and this is given as 8.25X8.25X9.5 inches. I have measured the mouth of the collector and that is 6.25 inches. The base only is 8.25inches.
This now works out at 501 m/litres of H20 per 1 inch of rain.
Please correct my maths if needs be before I throw in the towel.
Hailstone.

[steve]

There was something nagging at me telling me that the rain collector wasn't 8 inches wide...

But I agree with your new figure - actually I get 503 ml, but I don't think the difference is significant.

[hailstone]

Thanks Steve.
I will leave it at this point for now. I do not want to change the Console settings back to inches untill I get a 0.0 reading one morning and a couple of days free of rain.
I am still using my trusty Texas Instuments pocket calculator so it will do for me then if you get only 0.002 m/litre differance. I have a 0.5 m/litre syringe but I will not be busting a gut to use it when Davis say they only work to + or - 4%.
Thanks yet again.
Hailstone.

[hailstone]

Update.
See, I am a man of my word Steve.
Three runs with the widget back in place and reckoning in 25 mm's' all three calculations were 4.4 mm under using 500 m/litre dripped over 47 minutes average time period.
Before the last run I used the Cumulus fine tuner and set it at 1.23 mm.
This setting gave me a total rainfall of 75.2 mm for a reading using Cumulus rain total for this run.
I cannot expect anything more accurate than that, hence, I have crossed your palm with silver Steve ( Brian, cross me off your hit list please, Hi Hi ) I do not know how to operate the smilies, so I have used the letters HI which in wireless telegraphy means laughter.
Many thanks to all for your forbearance.
Let nothing you dismay.
Hailstone.

[steve]

Ah - that was you. I hadn't made the connection, even though I knew you were in Co Durham. I normally send thanks (eventually) by email, but as we're here - thank you very much.

I think my VP2 rain gauge was under-reading by a quite a bit when it arrived, now I come to think of it, but possibly not by quite as much as yours. I adjusted mine using the screws on the gauge rather than by using the Cumulus setting, though.

[hailstone]

If by adjusting the screws, a small amout of rain is left in the buckets and if temperatures drop below zero is there not a risk of accumulating an ice deposit in each bucket and possibly not of an equel proportion? This film of ice will increse over time when raining and temp. remains below zero surely? Here in the NE we do tend to get showers of rain during the winter months even though the temperature at ground level is zero. This happens when the wind is from the east and the north sea keeps the air temperature a tad above freezing. You are surrounded by sea Steve but in the North Atlantic Drift nonetheless which will keep the temperature above zero except for the odd occation or am I wrong.
I suppose the Davis electric blanket would solve the problem but, good gravy, at what cost?
Hailstone.

[steve]

Adjusting the screws doesn't cause rain to be left in the buckets. It changes the start position so that it takes more or less rain to make it tip.

[hailstone]

Roger!
I will master this beast if it is the last thing I do.
I will start again from square one tommorow.
The rain figures for the rest of the year have been knocked for six in any case.
Hailstone.

[hailstone]

I am now throwing in the towel.
I calibrated (or so I thought ) after 7 tries to finely get a reading of 25 mm for 500 m litres of water.
Fast foreward two days......
Today without touching any screws again and being meticulous as usual in measuring 500 m liters of water (lab flask used) I got the folloing readings

Start reading 0.0 mm.
1 st run end reading 23.8 mm. that is minus 1.2 mm.
Setting 2nd start to read 24 mm
2 nd run end reading 46.8 mm that is minus 2.8 mm.
Setting 3 rd start to read 47 mm
3 rd run end reading 68.2 mm that is minus 8.8 mm

I can now understand why there is a panic over Climate Change, at this rate if I keep on for two days an irreversible drout will be experianced in Co. Durham.
Any ideas?

Hailstone.