Home made standard rain gauge

Tactical

Been longing for a weather station for a long time.

Can't afford the luxury for the foreseeable future.

A standard rain gaue seems like a good place to start for something to construct.

So with that in mind I've done a quick search on the internet for standard rain gauge dimensions and I'm not 100% sure which sites provide accurate information.

I've more questions than when I stated.

1/. What are the dimensions of a standard rain gauge.
2/. Is a funnel used and if so what should the diameter of the funnel be?
3/. A graduated cylinder won't be too hard to source, I understand it should be 2cm in diameter. Should it be graduated in CC or is there a specific graduated cylinder I should be looking for?

Essentially I'm asking if anyone has built one or if anyone knows the actual dimensions of one?

Thanks in advance for any replies.

Trogdor

I don't know much about it but just thinking about it i don't think the dimensions really matter that much as long as the sides are straight vertical and the base is flat i.e the base, the opening and any horizontal slice in between have the exact same dimensions. Any funnel used would then have to abide by this rule as well with the rim around the top of the funnel having the same dimensions as any horizontal slice of the container. Once that is always satisfied i think any dimensions or shape you want is fine with a greater area at the opening giving greater accuracy. The side of the gauge can just be marked off in whatever increments you like using a standard ruler, or the ruler could just be stuck on to it either for that matter. And then the rainfall could just be read off in mm or inches but the accuracy might fall down a bit in trying to determine exactly where the water levels are by eye (would be to the nearest mm or 2 probably). Another important point would be to have the gauge as flat as it can be so that it wouldn't read higher on one side of the gauge than the other further reducing its accuracy. I think this would be the easiest way to make one.

The graduated cylinder i presume would be used to measure the water level to a more accurate degree, but if the water was being funneled into it with a funnel of greater area at it's opening than that of the opening on the graduated cylinder then a conversion factor would be needed (which would depend on the area of the funnel opening). You could make a similar setup up as above and use the ruler markings as an estimate gauge and then the water could poured into a graduated cylinder every once in a while and measured off accurately using a conversion factor. This would greatly reduce the error in reading the level by eye I imagine and would also mean that you would not have to worry about having the gauge perfectly flat as the volume of fallen water is ultimately being measured instead of the depth. The units that the graduated cylinder measures in wouldn't really matter as this could be worked into the conversion factor.

I don't know if there are standard dimensions or not but i suspect your best bet might be su campu or mothman on that point

Coles

I've made a good one, and while it's excellent for getting a good view of weekly or monthly rain totals, you'd be better to save up your money and buy a simple 'tipping bucket' gauge. There is no shortage of them on the market and if you don't want it hooked up to your computer there are very simple and cheap dataloggers that will store the information until you retrieve it.

I'll post some pictures over the next few days of the gauge I made.

pauldry

Yeah I made one out of a 2 litre water bottle while my gauge was broken.

First you need an empty 2 litre water bottle. Then you need a scissors and sticky paper and a ruler. Cant really remember how I measured the mms but they are fairly accurate.

Anyways You cut the bottle in half as straight as you can.

Turn the funnel of the bottle upside down and place in the other half of the bottle attaching with a paper clip.

Then and I think this is how I got the mm measurement fairly accurate - wait till a day of heavy rain like today. If they say there is 20mm of rain near your area(Belmullet and Claremorris and Finner in my case) measure the 10mm with a permanent marker on the rain gauge by guesstimating how much rain is in the gauge - not fool proof by any stretch.

Oh you need to place the rain gauge in something heavy to hold it from gales so I put mine in a bucket of sand with holes in the bucket for drainage.

This is a most unideal method of making a rain gauge but when I got my tip bucket working agian it recorded 45mm of rain over a 4 day period and the water one had 50mm so not too bad.

The downside is the homemade one had to be cleaned lots and then slugs started living in it.:P

Hope this is of some help but if you want more info just google how to make a homemade raingauge.

Su Campu

A simple way of getting an accurate rainfall amount Pauldry is by weighing the water collected:

1 mm of rainfall is equivalent to 1.00 litre (i.e. 1.00 kg) of water per square metre (at 25 °C, but never mind that). If the radius of your funnel is say 6 cm (i.e. 0.06 m), then its area will be 3.142 x (0.06)² = 0.0113 m². Remember this figure.

Pour the water collected into another (dry, pre-weighed) container and find its weight. Say you measure 35.5 g water. This is 0.0355 kg. Divide this by the area over which it was collected 0.0113 and you get 3.14 mm/m rainfall equivalent (this figure, by pure coincidence, is pi!!).

In this case, we can say that 1 mm of rainfall is equivalent to 0.0113 kg (11.3 g) of water collected. So weigh your water in grammes, divide by 11.3 and you have mms rainfall equivalent.

Now just accurately measure your actual funnel area, and use that figure instead.

Tactical

Many thanks for the replies, much appreciated.

I had planned on using a copper pipe, (offcut of a large diameter pipe of approx 4" diameter which I'll measure the internal diameter of shortly with a calibrated vernier caliper), to which I was planning on fitting a flat copper base. Then a graduated cylinder sitting inside, fed by a funnel.

The idea being that the copper vessel would be heavy enough to avoid tipping over and be tall enough to not be affected by any splashes, although it would be located in an open area that is grass rather than concrete.

I understand the funnel would be needed to offer a standard collection area size due to the narrow diameter of the graduated cylinder. The outer vessel would then collect any overflow should the graduated cylinder should conditions give enough rain.

I've certainly seen a few sites on the internet that give construction details for the plastic drink bottle solution and while these actually seem fine, I thought I'd like to have a go at something more professional, something that would be sturdy and something that would actually look nice (well to anyone interested in weather :eek:), all while using as many materials as I have to hand.

Su Campu

Tactical wrote: »

Many thanks for the replies, much appreciated.

I had planned on using a copper pipe, (offcut of a large diameter pipe of approx 4" diameter which I'll measure the internal diameter of shortly with a calibrated vernier caliper), to which I was planning on fitting a flat copper base. Then a graduated cylinder sitting inside, fed by a funnel.

The idea being that the copper vessel would be heavy enough to avoid tipping over and be tall enough to not be affected by any splashes, although it would be located in an open area that is grass rather than concrete.

I understand the funnel would be needed to offer a standard collection area size due to the narrow diameter of the graduated cylinder. The outer vessel would then collect any overflow should the graduated cylinder should conditions give enough rain.

I've certainly seen a few sites on the internet that give construction details for the plastic drink bottle solution and while these actually seem fine, I thought I'd like to have a go at something more professional, something that would be sturdy and something that would actually look nice (well to anyone interested in weather :eek:), all while using as many materials as I have to hand.

The nice thing about using a polyolefin container (polyethylene or polypropylene) is that they're low-energy surfaces, so the water will run off them easily, therefore reducing any residue remaining when you pour it out into the other weighing container (see my post above).

Tactical

Su Campu, you're a genius

I'll happily be using the copper pipe. I'll look for an internal collection container of the material type you've suggested.

While I source one, would it be acceptable if I used a clear lacquer on the inside of the copper vessel to reduce surface friction?

I love the scientific approach and will definately be using your method.

As time allows I'll be attempting to construct my own copper funnel too :eek: but I'll be constructing the collection vessel first

Su Campu

Tactical wrote: »

Su Campu, you're a genius

I'll happily be using the copper pipe. I'll look for an internal collection container of the material type you've suggested.

While I source one, would it be acceptable if I used a clear lacquer on the inside of the copper vessel to reduce surface friction?

I love the scientific approach and will definately be using your method.

As time allows I'll be attempting to construct my own copper funnel too :eek: but I'll be constructing the collection vessel first

Exactly, a waxy lacquer will do either. Just as long as it isn't soluble in water!!!

Failing that, any old PE or PP bottle or tupperware container (remember those?) will do as a container inside your copper pipe. Anything that will allow good run-off, as residue will contribute a large error for low rain amounts.

Tactical

I have a non-water soluble spray lacquer that I use on metal and water beads pretty well on it. I might even apply a car wax to it to ensure it performs well.

It'll do until I identify something with a suitable surface (as suggested by Su Campu) in a larger supermarket than local to me.

I'll post a photo of the outer vessel

tphase

this is what ME use, aperture is 400 cm2

http://www.vaisala.com/Vaisala%20Documents/Brochures%20and%20Datasheets/RG13-RG13H-datasheet-B010195EN-D-low.pdf

Tactical

My offcut piece of pipe has an internal diameter of 102.5mm which is 10.25cm.

This gives a collection area of 330 cm2 or 0.33 m2.

Now, I'm off to search the internet for a length of vessel that will avoid splashes from the ground. If the recommended length is longer that the length of pipe I have, I'll just mount the vessel on a pedalstal that is the same diameter as the vessel.

I see that the one detailed has a height of 39cm, so I'm guessing this is an ideal height to avoid ground splashes.

DOCARCH

Here's a simple one....

http://www.rmets.org/weather/observing/raingauge.php

....with jelly at the bottom! Yum yum.

Tactical

Have the pipe cut to 39cm and a 15cm piece.

The 15cm piece has been cut along its length and will be annealed before being flattened and cut into a piece for the base of the rain gauge.

Will update later as have a few jobs to attend to before I'll get a chance to get back to my little project.

Tactical

Base has been annealed, flattened (from a cut section of pipe), annealed and filed to size 15cm x 15cm.

All ready for soldering to 39cm long tube.

Positioned and flux applied.

Again, have to leave it for a while and anyways I can't located my bar solder at the moment but can always pop off to the plumbing wholesaler for another bar if I can't located mine.

Tactical

Found my solder

Base and tube have been soldered together and are currently cooling.

Next test will be to fill with water and check for leaks.

After that it'll be cleaning, lacquering and waxing

Will post a photo of the completed item.

Tactical

As promised some photographs, but before cleaning.

Leak test passed

The first shot is the overall rain gauge and the second is a closer shot detailing the soldering between the pipe and base.

Will post better shots of the cleaned item placed in its collection location.

Coles

Nice job. You seem to have a fairly clear idea of what you're at so I'm going to wait until you've finished before posting some pictures of my gauge.

Tactical

Its finished, for the moment...

Just needs a good clean up after the annealing and soldering. That won't be happening until Monday evening or Tuesday at the earliest due to other committments for the weekend.

I have planned to make a funnel providing I have enough copper to make a funnel of a diameter a good bit larger than that of the vessel (102.5mm inside diameter)

So post away your pics

(Actually, I started another thread about home constructed weather instruments as I'm curious to hear about other peoples experiences and see any constructions they have undertaken)

Coles

I wanted my rain gauge to give accurate measurments for low levels of rain (1 to 5mm), but also to give good measurments for medium term rainfall totals (max 150mm, typically one month).

I decided to use a 2" Marley Pipe to construct the gauge as it was cheap and easy to work with, but also because as it is white any evaporation from the gauge is minimised so the accuracy of long term low level rainfall periods is maintained. A funnel at the top of the pipe catches the precipitation and feeds it directly into the pipe.

The ratio of the area of the funnel to the tube is 8.65 to 1, so every 1mm of rain fills the pipe by 8.65mm. A smaller diameter pipe would give a more accurate reading for very low level precipitation events, but it would also limit the maximum total or the lenght of time the gauge could be left unattended. As it is, the gauge has a total lenght of more than 2m and is capable of recording 150mm of rain.

Inside the pipe there is a float which is connected by a lenght of fishing line to a marker on the outside that indicates the exact level of the water inside the pipe. This is a great system and it allows a very quick and easy reading without touching the gauge. During extreme rainfall events I tend to take a reading every 15 minutes, but sometimes I only look at it once a week. I usually empty the gauge (screw cap at the bottom) when it's almost full.

It works extremely well and it was well worth making (total cost €30), but it's too much work to take daily measurments. I would definitely recommend a simple tipping bucket gauge with an event datalogger, and while it might cost €80 to make it would be infinitely more useful.

Tactical

Great account of what you've done

I'm unfortunately not in the position to purchase an automatic station or a datalogger so manual measurements it is for me at the moment.

I do intend to make a funnel for the rain gauge (providing the material available to me will allow me make one of sufficient diameter, otherwise it'll be a purchase of a cheap plastic or stainless steel one...).

The I intend putting a smaller collection vessel, such as a graduated cylinder within the rain gauge, fed by the funnel.

That way I can efficiently collect and measure / weigh small amounts of rain fall and in the event that I log over a week or so, any overflow from the inner collection vessel will overflow into the outer vessel allowing collection and measurement.

Besides, I like the idea of the "old school" instruments.

The Valentia Obs at Caherciveen have a fantastic collection of old instruments at Westwood House on-site. Fascinating stuff.

Coles

Here's a picture. The overall lenght of the gauge is about 2 meters. The funnel that is fitted at the moment is 150mm diameter, but I have larger one (250mm) that I fit when I want to take more accurate readings during a particular storm.

Tactical

I know I'm resurrecting an old thread, but I just wanted to share a mail order source of graduated cylinders

http://radionics.rs-online.com/web/c/?sra=oss&searchTerm=Graduated+cylinder&x=0&y=0

Almost a year on from the original construction and I'm only now finding the time to make the copper funnel for the gauge

The car wax has worked perfectly as a low friction surface inside the vessel. However, now it's getting dark early in the evenings again, time can now be found to progress the item.

It's had a good bit of use over the year and hasn't once fallen over so I seem to have hit a reasonable height to base width dimension. The copper funnel will (hopefully) be heavy enough to stay in place in windy weather.