# How to measure voltage differential across different altitudes

Imagine two points, one directly above the other.
Point A - 10,000 feet (PA)
Point B - 20,000 feet (PB)

Imagine there's voltage potential between those two points.

Questions:

1. How could you measure the voltage between those to points?
2. What if the points were at the same altitude, but 10 miles away from each other. How could you measure the voltage potential? (i.e. PA is in Ohio at 10k feet and PB is in Indiana at 20k feet altitude - ground distance between the two points is 10 miles)
3. How could you determine if the potential was oscillating?
• What about the distance do you think makes this different than any other voltage measurement? Aug 18, 2020 at 18:14
• Be careful when writing "10m", I (and probably many people) read "ten meters", not "10 miles". Aug 19, 2020 at 7:45
• @CortAmmon the goal was to find techniques across great distances. One of the solutions using weather balloons probably requires FAA registration, something you wouldn't find if you're measuring a circuit in your basement. Additionally, my goal was to see if other people were working on a similar scale and would be interested in joining efforts. Aug 20, 2020 at 0:29
• @Jean-MariePrival thank you for the insight, I've updated the original post to avoid that problem Aug 20, 2020 at 0:30
• "techniques across great distances" -> ludicrously long cable + plus standard mid air plugs :-) Seriously, no idea how to exactly measure a potential between mid air points. Air to ground can be estimated to a few magnitudes when lightning strikes (no measuring instrument I know of could survive) a prepared lure, aka lightning rod, or by examination of fulgurites, but I am not an expert ...
– user20217
Aug 20, 2020 at 10:16

1. How could you measure the voltage between those to points?

I imagine you could measure the potential difference using weather balloons. Send one balloon up to 10,000 ft (Balloon A) and one to 20,000 ft (Balloon B) with wires connecting them to a voltmeter. The challenge here is to account for the wire resistance, which, if the potential difference is low, will in all likelihood interfere with the measurement. If the difference is too low to be measured, you would have to amplify the voltage and then account for the amplification and wire resistance.

1. What if the points were at the same altitude, but 10 miles away from each other. How could you measure the voltage potential? (i.e. PA is in Ohio at 10k feet and PB is in Indiana at 20k feet altitude - ground distance between the two points is 10 miles)

I would try using weather balloons again, but obviously Balloon A and Balloon B would be at the same altitude but 10 miles apart from each other.

1. How could you determine if the potential was oscillating?

Instead of a voltmeter measure with an oscilloscope. There's going to be noise no matter what; what oscillations are produced by noise and what is actual oscillations is a judgment call. I would say that truly oscillating potential difference is likely to be low frequency, so to filter out high frequency noise connect the circuit to a low-pass filter before processing with the oscilloscope.

Another way to determine oscillations is to measure the voltage with a data logger and post-process with computer software; any programming language that can easily manipulate large amounts of data would be sufficient, even excel would work. Plot the voltage vs time using a linear regression model to smooth the noise out. As an example, python's numpy has a regression function called polyfit. With a linear regression model and a moving window you will truncate the beginning and end of the dataset, but that shouldn't matter if you have a lot of data.

• Would having such a long wire be subject to being influenced by voltages at other altitudes? i.e. if there's a strong potential between 10K and 13K but I'm measuring between 10K and 20K could that induce voltages? is there a way to measure without using wires? Aug 20, 2020 at 0:40
• I wonder if the "two ballons with a with a wire between them" runs afoul of point #6 "knowingly operating a balloon that creates a hazard ..." overlookhorizon.com/flight-safety Aug 20, 2020 at 0:45
• I think you would need a tether to hold them at the correct location and altitude; that tether can accommodate a wire to measure the potential difference at that altitude. Since they would be on a tether anyway, it makes sense to just tether them together. From that flight safety page it seems that you just need FAA permission to launch them. If you can't tether them together, you can measure the potential difference at each altitude from the ground and find the difference. Aug 20, 2020 at 1:37
• As for the influence of voltages, good wire insulation should prevent that. However, there is the possibility of eddy currents if the electric field is moving. I don't know how this could be done without using wires. Perhaps radio transmitters could be used instead. Or, since you would be measuring electric fields, an EMF meter? Aug 20, 2020 at 1:40