Rain sensor with snow.

[RCE]

Just wondered if anyone had tried fitting a heating element inside the rain sensor to measure snow fall.

[Repairman77]

Just wondered if anyone had tried fitting a heating element inside the rain sensor to measure snow fall.

Yes I thought about it and found an easy answer in a WX station book, a small bulb, perhaps 12V 5W, fitted just inside the rain collector but you need to be able to power it from a mains transformer as a battery wouldn't last that long. It would be an idea to fit a thermostat in series with the lamp, which came on at perhaps 5 degrees above zero. It may be possible to modify an old fish tank thermostat (a separate one from the heater element - not one of the combined ones) but I haven't tried this. Another problem may be keeping any mesh above the top inlet warm enough to melt any snow that settled on it.

However as we normally only get snow at my location for a few days a year (this year is exceptional) whether it would be worth the trouble is debatable. Would be quite useful for those at high elevations North of the border in the UK I guess, as they have a lot of snow in the Winter months.

Maybe a job for the Spring or Summer?

Mike.

[RCE]

I was thinking of a 5W lamp as I guess the glow of the rain collector would look good on a winters evening . Power wouldn't be a problem as the rain gauge is next to our greenhouse that has mains power.

As for control was thinking of using my home automation system to trigger the mains supply on/off if temperature low.

May try this as I need to fit a grill anyway and don't want a sudden flow of water as the snow naturally melts.

[beteljuice]

It is only any use as a possible means of clearing your rain collector.

Measurement of snowmelt is somewhat meaningless as you would need to know the 'type' or density of the snow during any particular time period.

Then when you know that, there is a formula which gives an estimation of snow depth.

[RCE]

It is only any use as a possible means of clearing your rain collector.

Measurement of snowmelt is somewhat meaningless as you would need to know the 'type' or density of the snow during any particular time period.

Then when you know that, there is a formula which gives an estimation of snow depth.

My plan is to measure precipitation, not snow depth. It will also (if it works) mean I don't get a rain reading when the thaw begins.

I have now adapted the rain gauge with mesh filters, and fitted a ceramic resistor to provide the heat source, testing in the house it raised the temperature of the box by ~ 30' over ambient this was with about 3W @ 5v so can increase a bit if needed.

Hopefully will get chance to fit outside tonight and give it a try by loading it with snow, let it sit an hour, then power it up and see if it works.

[Repairman77]

It is only any use as a possible means of clearing your rain collector.

Measurement of snowmelt is somewhat meaningless as you would need to know the 'type' or density of the snow during any particular time period.

Then when you know that, there is a formula which gives an estimation of snow depth.

My plan is to measure precipitation, not snow depth. It will also (if it works) mean I don't get a rain reading when the thaw begins.

I have now adapted the rain gauge with mesh filters, and fitted a ceramic resistor to provide the heat source, testing in the house it raised the temperature of the box by ~ 30' over ambient this was with about 3W @ 5v so can increase a bit if needed.

Hopefully will get chance to fit outside tonight and give it a try by loading it with snow, let it sit an hour, then power it up and see if it works.

Interesting RCE; I hadn't thought of using a ceramic resistor; have you got a pic of the modification which may help others considering this. I take it you have isolated it from the actual plastic to stop it melting the casing?

Mike.

[RCE]

Interesting RCE; I hadn't thought of using a ceramic resistor; have you got a pic of the modification which may help others considering this. I take it you have isolated it from the actual plastic to stop it melting the casing?

Mike.

The resistor I used is one I had kicking round (used with motorbike LED indicators to maintain the flash rate) so it is shrink wrapped and a nice size to dissipate the heat. The surface temp got to about 60'C which should be OK with thermosetting plastic (especially with the low ambient temperatures). Will grab an internal photo in case it works!

Not sure if it wouldn't have been better lower down the case, but the size dictated the location. If I was buying the stuff would probably buy a couple of 4ohm resistors to keep the bulk down so they could be stuck to the side lower down without catching on the balance mechanism. Once I looked inside realised getting a 5W lamp in there would be a challenge so gave up on that idea.

Will report back either way how it goes.

[gemini06720]

For those of you interested, here are some information about the Davis Instruments 'Rain Collector Heater' for its Vantage Pro weather stations.

From their documentation:

"The Rain Collector Heater may be used to protect the Rain Collector’s internal components from freezing and/or to measure the moisture content of snowfall. When the heater is on, it is capable of melting snow at a rate of 1/4” (6 mm) of liquid precipitation per hour. It may not be able to keep up with larger rates of snowfall."

"The Rain Collector Heater warms only the inside of the Rain Collector and the cone itself. For some weather conditions, it may be necessary to add a lamp or heater beneath the unit to keep the drains open."

I have attached a picture of the unit Davis calls the 'Heater Assembly'

2010-01-07_00001.png

The 'Heater Assembly' includes a heater element (looks like a wire wound resistor), a thermostat (set to interrupt the power to the heater element when the temperature at the thermostat reaches 110˚F or 43˚C), and terminal block for connecting the power cable.

Also included in the $195 US (retail) package are:
- a wall transformer with power unit (a plastic box with a switch and an indicator light that is used to connect the wall transformer to the heater cable via, what appears to be, an inline fuse),
- an insulation blanket (that installs against the internal side of the rain collector cone),
- and 50’ (15 meter) of heater cable (22 gauge, two twisted-pair cable).

No, I do not have a 'Rain Collector Heater' on my weather station ... I could not accept that high of a price of a resistor, a thermostat, a power transformer and the cable!

Maybe, if Davis had also included a sensor that automatically switches the power on when the ambient temperature goes below a set point and that automatically switches the power off when the ambient temperature goes above a set point ... maybe I would have bought the 'Rain Collector Heater'...

[beteljuice]

Somewhere (unfortunately can't find it now), I saw a mod with a thin film ceramic resistor epoxy glued to the 'inside' of the chute.

The author was very happy with results (he used an old bi-metal thermostat that went to frost level), and he didn't melt his bucket !

Trouble is I can't remember any of the values ! -

Another solution I've read about is 'Reptile' wire / tape, apparently it turns itself on when cold, I suppose you could also try a 'brew' belt, but that would be quite large.

Late Footnote: Even expensive 'professional' kit usually switch off the heater when eg. less than -6.0C - fighting a losing battle and saving energy.

[Gina]

Been thinking about this myself. I have added an extra funnel held by a plant pot over the rain gauge to improve readings in light showers. At present the whole lot is under something like 8 inches of snow! My thoughts are to use a bigger funnel to give a 0.1mm resolution (the present one is 30% bigger than the gauge area). Also, to enclose this in a casing of some sort which could be heated. Running power would not be a problem.

I had a career in computers and electronics/electrics which I chose instead of the more usual marriage and children. I still have an interest in these things

[Gina]

Tried to post a diagram but it came out far too big I'll have another go later.

[beteljuice]

BTW - for those of a mathematical bent - the spoon 'size' of the Fine Offset rain gauge is 0.2794mm

Although I would still expect you to have to do a few tweaks if change your 'collector' size.

[Gina]

Here are the two different funnel arrangements. The small funnel is what I have now but I'm going to use the large funnel instead and have a wood preserver container which will fit between the top of the large funnel and the flower pot. I could then put a heater in that. I can insulate the container with polystyrene wall insulation (sort that goes between wallpaper and wall). If freezing up of the rain gauge is a problem, that could also have a heater.

Small-Funnel.png

Large-Funnel.png

[Gina]

Modified design for rain gauge with the large funnel. The outer casing is now a plastic bucket that wood preserver came in. By cutting half the spout off the funnel it will fit nicely above the rain gauge with it's top bit sitting in a large hole in the bottom of the bucket.

Rain_Gauge-3.png

[Gina]

Here's a photo of the finished rain gauge (sitting on a little table). See see attachment for cross-section.

Rain_Gauge-4.png