Electronics > Beginners
Measuring voltage (and frequency) of spark
joeqsmith:
--- Quote from: petert on December 20, 2019, 01:27:11 pm ---Hello,
I experimented with a piezo crystal from a lighter to generate a high voltage spark. A coherer was able to detect the generated EM wave (from the spark/spark gap) in close proximity.
Now I am trying to generate a spark with a coil that has the same effect. I charge a coil/inductor with a 4.5V battery and when I break the contact or make it, a spark is generated as expected.
How could I measure the spark voltage (and frequency) between the two leads? I am worried it might damage my scope.
--- End quote ---
Did you made your coherer and can you post a picture of it?
When I was looking at my piezo crystal lighter, I was looking at the current rather than the voltage. To look at the voltage on my ignitions, I normally will use a capacitive coupled divider. For the lower frequency current, I have a wide band transformer. I kept one of my first DSOs just for this sort of potentially destructive experimenting.
T3sl4co1l:
--- Quote from: imo on December 21, 2019, 04:27:41 pm ---I doubt so..
The HV coil generating the sparks and the LC tank (or a resonant antenna) are two different things..
You need a resonating "something" wired/coupled to the spark gap (see above the wiki) in order to produce your "frequency of interest"..
--- End quote ---
Measure some coils, or try it yourself. Or write it out from E&M theory. I think you will be pleasantly surprised. :)
Tim
petert:
--- Quote from: tautech on December 20, 2019, 08:45:50 pm ---1000:1 probes for scopes are not that expensive.
Look up Joe Q Smith's DMM test videos where he uses grill ignitors and builds a 1000:1 probe so to see and measure the waveforms.
--- End quote ---
I suppose you mean this video?
Other possibly relevant videos:
Interesting but not directly related:
tautech:
--- Quote from: petert on December 22, 2019, 09:01:46 am ---
--- Quote from: tautech on December 20, 2019, 08:45:50 pm ---1000:1 probes for scopes are not that expensive.
Look up Joe Q Smith's DMM test videos where he uses grill ignitors and builds a 1000:1 probe so to see and measure the waveforms.
--- End quote ---
I suppose you mean this video?
--- End quote ---
:-+
Yep, all those !
We can see from Joe's investigations that grill ignitor voltages aren't that high and a 1000:1 probe capable of handling 15kV should be ample to view their waveforms safely.
See if you can find any Pintek HV probes sold locally:
http://www.pintek.com.tw/files/pintek/HVP-provided-Fig.pdf
petert:
--- Quote from: joeqsmith on December 21, 2019, 05:06:19 pm ---Did you made your coherer and can you post a picture of it?
--- End quote ---
It's not the clearest, because I used it several times already and the flexible tube has become a bit tarnished.
I also adjusted it several times (moving the screws to adjust the distance) until I found a working "configuration", tapped it to decohere it, so that some of the filings are "spread out" on the screw threads.
The filings are of Cupronickel, a mix of copper and nickel (75 % Cu, 25 % Ni).
Full resolution pic (click to zoom):
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