Measuring rain or snow by means of static charge?

[cdev]

Its my understanding that rain and snow carry a static charge. Have any of you ever attempted to measure (or indicate the presence of same) by means of this charge? How did you do it?

I recently saw a YT video where a substantial charge was being collected on an antenna and was arcing. It must have been a very high voltage to draw these arcs.

Yutube channel? I think it was Mr Carlsons Lab (I may have the spelling wrong)

This leads me to think that it may be interesting to measure this, if it can be done in a way thats safe to your hardware. 

The static was arcing due to a snow storm.  It was a long (dipole?)  antenna.

[TimFox]

Was that arcing due to accumulated charge along the antenna, or intermittent conduction through the snow along or across the wires?

[T3sl4co1l]

Ah yeah, I recall that video, Mr Carlson's indeed.

You may want to be careful to avoid induced field effects -- you could very easily make an accidental Kelvin dropper, I suspect.  Maybe kind of unusual for an antenna, being that the structure is usually wires not cages, and usually off to each side, not crossed; but weird shapes are used from time to time, and maybe with the right wind it could happen, hey who knows.

Oh, also that assumes some means of reference: it works when water drops off one electrode, in the field of the other; free raindrops/snowflakes are charged at whatever they start with from the clouds and can only be deflected by electrodes they don't touch.  But that can easily happen with some colliding with the antenna then dripping on down the way.

So with that consideration covered, what's left should simply be charge deposited by particles in contact, which comes from the atmospheric potential.  Which is, well, there you are.  Hook up a meter and log away!

There's still one thing: charge removed by particles colliding or dripping off the element.  If its voltage is held near earth, you can at least null the charge loss (or gain, when regenerative as above) due to dripping.  Not sure what can be done about triboelectric charging though; especially if it's something like freezing rain or sleet and the elements get caked with snow/ice, and so you have snowflakes rubbing against an insulating layer, as well as sometimes landing in place depositing charge.

As for avoiding it, easy enough to galvanically ground it of course, which often happens incidentally with the use of a balun, tuner, or what have you.


Ed: heh, would be interesting to plot this as just some random ancillary data on one's weather station -- if so equipped.  I'm not sure that it would really be very meaningful or interesting by itself, but it might be one of those oddball things that interesting correlations can be found on.  Like varying with intensity of storms, or ionospheric activity or something.

Tim

[Kleinstein]

I would expect the charge the raindrops start with to vary. So a measurement of the charge of the rain drops may be an interesting experiment, but I would not expect it to replace a conventional rain measurement. It would likely need more measurements too, like measure the size and overall rain too.

It could still be tricky to measure small currents / charge pulses in a humid / wet environment.

[T3sl4co1l]

Varying, you mean of individual particles?  Hmm, that might be interesting.  You'd need something quite other than an antenna to do that, of course.

Else -- in aggregate that all averages out, but you might then mean with respect to weather conditions, which would also be interesting, and would probably use antenna-like hardware.

Hmm... I wonder what you'd do for that... maybe an electrode array, each electrode attached to either a bit of a transimpedance amp (since we're measuring fairly small currents here), or an integrator / charge amp (for obvious reasons), or perhaps even doing it at high frequency say with RF amps or tuned networks (since there will be a transient as the particle splats in place -- moreso for rain than snow).  The array wouldn't so much for resolution, as to give a wider range of rainfall densities to track events more discretely -- not so much for imaging purposes as just for getting good statistics / dynamic range.

Alternately, could do something like an insulating pipe with charged electrodes around it, and measure the deflection from vertical (mind, after falling some distance away from wind, to avoid situations where it's blowing sideways, as sometimes happens ).

Tim

[Nominal Animal]

Because snow is triboelectric, the polarity and the amount of static charge does not really depend on the amount of snow: it depends much more on things like air velocity, pressure, temperature, and relative humidity.  (In very cold, air has very little humidity, and the static charge in snow due to triboelectricity tends to be larger.)  Even the rate of accumulation of the snow affects the charge, because the weight acts like a strain on existing snow.  Plus, when it is windy enough (stormy), snow gets thrown around even without it raining any additional snow: snowdrift.

I'd say it's as useful as measuring the potential difference between two isolated electrodes in air, one a meter or two higher than the other, for predicting the weather.

Assuming the lower electrode is not very high up from the ground, we'd expect around 100 V/m difference.  The exact potential would be interesting, but it would not be that useful for predicting the weather, if you consider thunder and rain different from dry thunder.  It should be indicative of the likelihood of thunder, but that isn't really weather, because thunder does not necessarily mean rain or snow...  Similarly, the static charge in snow due to triboelectricity isn't dependent on the amount of snow, but it could be otherwise useful information; maybe "crispiness" of the winter?

[LaserSteve]

If you shop around on Ebay you can find working Vibrating Reed Voltmeters. Your next stop after that  will be constructing a rotating sector  Field Mill. Beware of so called field meters / non-contact  charge detectors without moving parts as usually they make some pretty harsh/crude  assumptions about the target they are used with.

Do not stick your finger onto the detector slot portion of an active Vibrating Reed probe. Unless you like severe shocks. Many of them work as a bridge circuit where a voltage controlled internal HV source is adjusted to null or equal the external field.

 I actually like the ones made for calibrating Xerox photocopier drums more then the lab grade ones.
They have better dynamics and sensitivity  at the low end then most lab grade probes.

Often the Electrostatic Voltmeters on Ebay by Trek or Monroe will be missing the probe. Make sure you get the whole unit.

Trek and Monroe US  Patents often have workable schematics.

Steve

[Doctorandus_P]

https://hackaday.com/2020/03/26/whirling-shutters-on-this-field-mill-measure-electrostatic-charges-at-distance/