Hi all, I’m looking to make a simple oscillator with a screen readout, battery opersted, that can have long metal spikes attached (say up to 40cm long) to push into the ground to read what resonance the land is operating in. the range needs to be very low between 400-500Hz not MHz or lower with an ability to read subtle changes instantly.
Does anyone have an idea where to start creating one? I’d like to be easily able to make a number of these to order if possible.
Hi Samantha
A bit skinny on info.
Variable frequency or fixed
Sine, square, pulse, triangle.
Voltage
Power required.
Frequency changes or amplitude changes.
Some sort of block diagram might be useful
I would think if you are trying to measure “resonances” you would be looking at variable frequency and measuring for dips and spikes in amplitude. series or parallel resonance.
If you want instantaneous results as in tuning for resonance you should be looking at analog meters. DMMs or digital devices will be far too slow in acting. Analog meters still have their place.
Cheers Bob
Hi gator
That would be half wavelength for an electrical signal in free space.
Speed sound pressure in air is 343M/sec so half wavelength would be about 0.4M.
Speed of sound in soil is significantly faster and depends on to a large extent on type and compactness of the soil
I am not too sure of exactly the object is here so will await more info.
Cheers Bob
it’s to plunge a metal probe into the ground and read what the land is resonating at. The earth resonates at that frequency in certain places. Not to be used above ground.
Hi Samantha
That does not answer any of the above questions.
I have no idea what you need to do that. Someone on the forum might.
If you know please share then we might have a chance.
An oscillator of some flavour is not terribly difficult if that is all you want. There are volumes and articles on the subject everywhere. It is what you want to do with it is the more strange part. After all it is probably not the sort of thing most people would do very often.
Cheers Bob
Hey @Samantha280626,
Interesting project! Some extra info about the usage may be useful (I’m not a geoscientist after all!), but I can make some guesses at the general idea.
I would think an oscillator is somewhat unnecessary here. While it could definitely be used, I think a much easier alternative would be to use a Geophone. This is effectively a ground microphone, designed to pick up vibration frequencies from the earth, and while it is listed as having a frequency range from 10 Hz to 240 Hz, a quick look at the datasheet shows that it should work perfectly fine for your 400-500 Hz range.
Please let me know if this suggestion is way off, as I may be misinterpreting the question. It’s also possible you could get a geophone for cheaper than this, I haven’t looked into specifics very much.
Hope this helps!
Now this answer is getting really close! I wondered if this would work but it is about how deep you can put the receivers to pick up the wave.
One can alter the wave with various things and we need visual tool to see if what has been tried out worked to alter it. Soil is a living organism and as such has an optimum wave form that needs to be tuned into and activities altered that maximise this capacity. A bit like being able to sit in a room of noise and focus shutting out everything else. Soil can do this too.
I found this but no idea if it’s good enough or could have some receiver attached?
https://www.ebay.com.au/itm/166707698359?_skw=low+frequency+oscillator&itmmeta=01J8NKTSR6ZVBTCW473PT5EX1C&hash=item26d08d9ab7:g:-bMAAOSwoH9mF4GX&itmprp=enc%3AAQAJAAAA8HoV3kP08IDx%2BKZ9MfhVJKlL2ZtZ%2Bt%2FFE9N8ytw2%2BMvgFPR2Fk9pj7bVvlNOVxqngIP04wKw%2FLgxXgLEuaXWMG7pIN%2FMf%2BoCHPBJcKSI%2BdIK8M7sgX6FWVlGqf4W4%2FQePHJrn1hbd%2BuwrI%2F19vFdpXG5iSn7%2Fu%2FMelXiiUEtxyIIrsVsPbCdUOxcGqpzfIldWanWV75dRqvdIFG9MUoCDjKLGPK1U1WqlZVLC3KU4zncgpbwcSpRyPnJKBW–MpXZqHJXl35EkBmPREDp9ukAsEEt%2Bkd4kN18A5H8%2Fu3We8Oq86a1LWjXceOM7nMrRD2FQ%3D%3D%7Ctkp%3ABFBMopzrs8Vk
The Earth resonates at ~8Hz. That frequency doesn’t change between locations, but you might be trying to detect where it is stronger and weaker. If you are referring to soils resonance then that is measured using a test column and vibration sensors, not stakes. Ground resonance is measured directly, but not over lengths as small as 40cm. And those frequencies are both much lower than 400Hz. So it is not clear exactly what you are trying to measure.
To use stakes pushed into the ground to measure vibrational resonance you would apply a force sensor of some type between the two pieces while vibrating the ground over a range of frequencies and measuring the response at each frequency.
Generating the vibrations would simply require a motor with an unbalanced shaft and a variable speed drive. How big that would be and how you would mount it depends on the ground.
Measuring the response is the tricky bit, and that’s what your question is directed at. At 400Hz that is probably above the range of a resistive strain gauge. But a Piezo sensor would handle that frequency, and could be configured for adequate sensitivity. Selecting the correct sensor is the place to start because that will determine the other components of the project. There is a good discussion on selecting an appropriate piezo sensor here: 002_sirohi00_jimss.pdf (utexas.edu)
Thank you for the explanation.
I am confused by this because yes I’ve read the earth resonates at 8 Hz but also at 432Hz so I’m not sure what part of the earth it is referring to to be so disparate?
Hi @Samantha280626,
That link you sent is a test device for crystal oscillators. It is not exactly designed to be connected to a receiver of any sort, it’s also generally designed to be used at higher frequencies than what you are dealing with, as crystal oscillators are typically much higher frequency (MHz-GHz).
Hope this helps!
thanks Zach I think i will forge ahead with your geophone idea ! now to figure how to put it down a hole!
Hi Samantha
If you want to generate a signal and alter the wave type and see what you are doing you really need a Function Generator. Most will go down to a couple of Hz or less and should cover your frequency requirements. I think mine goes down to 0.1Hz but I would have to dig out the specs and have a look.
For interest mine is a UNI-T Model UTG932E. Quoted frequency 1µHz to 30MHz. Don’t know what use the 1µHz is but looks good for marketing purposes. 1µHz is one cycle every 1000000 seconds. Pretty slow.
Cheers Bob
Thanks, I’ll check it out. And it can show 450Hz easily too?
Hey @Samantha280626,
From my understanding, the Schumann resonance or the frequency at which the earth vibrates is 8Hz (7.83 Hz to be exact).
432Hz is commonly cited as a frequency that resonates with 8Hz. This means that something vibrating at 432Hz, most commonly audio signals, will also output wavelengths at certain points at higher and lower frequencies and for 432Hz this includes 8Hz.
If you are planning on measuring the resonate frequency of the earth you may detect something measurable around 432Hz but sampling around 8Hz will give you the most accurate reading of the ‘true’ frequency.
Hope this helps!
Hi Samantha
I reckon that might be within this instruments range.
Cheers Bob
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