Is this signal a hardware issue or is my ground always moving?

[Goemi]

Hello,
i am from Germany and a new member of the community. I installed my Raspberry Shake RS1D a few days ago. It is installed in the basement directly on the tiles of the concrete floor. I use a short LAN cable to connect the Shake to the WLAN router. The router is about 1.5 meters away. The Raspberry Pi i use is a 3B+.
I know i live in a very noisy place with a big road nearby. But when i set the filter to regional 0.7 to 2 Hz i have a continuous “noise”. Is this a issue of some hardware? Maybe the power supply? Or is the distance between the RS1D to close to the WLAN router? I turned everything off in the basement (the heating with all pumps, the NAS, the washing machine, etc.) but the “noise” is still there.
Can i do something again the noise? Or is this singal real?

Greetings,
Michael

[Stormchaser]

Hello Michael, welcome to our community!

I have looked at the daily views of the data your Shake is recording, and the signal appears to be real.

As you can see, it seems to be a cyclic appliance that turns on and off at more or less regular intervals, and mainly during daytime hours. At nighttime the influence on what you record is definitely less.

Do you perchance live close to an industrial plant, or large apartment/office buildings, that may have such appliances turned on and off regularly? It could be a heat pump, or air conditioning equipment, or something close to these.

[Goemi]

Hello Stormchaser,
thank you for your reply.
I think what you see in the recording is the big street near to me and the regular intervals are triggered by the traffic light.

This is what it looks like when its “quiet” and with the filter “Hyper Local” 3.0 - 20.0 Hz.

But i am wondering what this Signal is:

This is the same time period but with the filter “Regional” 0.7 - 2.0 Hz. This waverform is like a groundnoise from the sensor.

So i thought that could be maybe a problem of my powersupply or something.

[Stormchaser]

I have taken time to review the data your Shake records, and that signal (the constant line below 3-4 Hz) is indeed constant, with very well structured pulses at regular intervals, if one zooms back a little bit.

I have also tried to see if some of the appliances you listed (router, power supply) that I have at home would generate such a signal, but without success.

I put the Shake very close to the PS unit and my router, but that signal did not appear. You can however try to switch your PS unit, if you have another available, to see if that was causing this wavey signal, or also maybe move the Shake to other locations in your house, to see if the signal continues to appear. It would be interesting to see what you can capture in different positions.

However, I have similar constant noise lines (at a bit higher frequencies) due to PC fan noise and other appliances, and they are a part of my local noise environment.

[Goemi]

I tried a lot of different things over the last weekend. Lastly, I switched the Pi3B+ to a Pi4. I also changed the power supply and the LAN cable. All I left old are the parts from the DIY RS1D kit. I also changed the location and moved from the basement to the 2nd floor. The new temporary spot is on a windowsill of an outside wall.
This has changed the station ID to R1053.

But the “noise” is still there. Is it possible to disconnect the geophone and check the Raspberry Shake circuit board with an open input? Or will i damage the board with this test? Is it better to connect a resistor instead of the geophone?

And now i have another question:
I will switch back to the Pi3B+ is it possible to delete the unused station ID after the change back?

Thanks in advance.

[PhilipPeake]

I don’t know how feasible this is, but what might be a good test would be to take the Shake to a different location, preferably outside the city.

[Goemi]

Testing somewhere else would really be the ultimate test. But I need a quiet place with a LAN connection. And that’s a small problem.
So I thought I can test the hardware. If this hardware test is then OK, I know that this signal is really present and an error can be ruled out.
But I think I’ll buy a cheap USB WiFi stick, take a big power bank and my portable hotspot and drive somewhere in the “woods” and test it.

[Stormchaser]

In this Philip anticipated me, as I wanted to advise a similar approach.

Even a friends/relative/colleague’s house could be a good testing spot, if it is sufficiently away from your location so that you will definitely be reading different signals.

Naturally, if you have the chance to go to a quieter place away from the city, all the better, since it will provide you a very good low-local noise environment to analyse. In the case you have no network available in this location, here’s our guide on how to use the Shake in that particular situation: Offline and stand-alone applications (like classroom demos) — Instructions on Setting Up Your Raspberry Shake

[Goemi]

Yesterday i had the time to test my Shake in a different location. And you are right!

It isn’t a hardware issue. My ground at home is permanently moving at a low frequency. It would be interesting to know where that “hum” came from.

Thank you for your great support!

Attached are a few pictures from Swarm for comparison.

At home:

Away:

[Stormchaser]

Hello Goemi,

Glad to hear that you were able to do a full comparison as you have shown! It is indeed very interesting to see the differences (the spikes in the Amplitude vs Frequency plot pop out very well in the first set) and it will also be interesting to try and discover where that very low frequency “hum” comes from.

Happy to help, and enjoy your Shake!

[PhilipPeake]

Well, that was a worthwhile test. At least your mind is now at rest about the hardware.
I don’t know how practical it is, but you might like to try different locations around your home to see if you can find somewhere that is a little quieter.

Determining what the vibration is coming from may be a little challenging (and doing anything about it even more so!). I have been surprised how far these vibrations travel - I suppose I shouldn’t have been, since I have seen earthquake signals from the other side of the world.

Since it is more or less constant, my guess is that you may be seeing vibrations from something like a large pump? Water supply or perhaps sewage?