Spikes in Recording

Hi, I have Spikes in my recordings pretty regulary. The RaspiShake is sitting in a metal case, only the seismometer is outside. Those Spikes are occuring every few hours. I did check for it on the Data View online as well as on the downloaded file via Swarm viewer. So this should be an issue within the process of measuring, amplifying, ADC, archiving.



Welcome to the club Thomas :slight_smile:
If you do a search on “spikes” you will find quite a few long discussions on these.
There have been multiple theories as to the cause, some of which are (in my opinion) occasionally correct. Speaking purely for myself, I have become convinced that the ones I see are due to heating/cooling of the building/concrete pad that it sits on. (It’s in a 30’x40’ pole barn with a concrete slab floor.)

In my case, it’s a shake/boom and the spikes only occur on the seismometer trace. It it were RF interference (which was a hot contender at one point) it is highly likely that it would affect both channels.

If I had a bit more spare money to buy another device, it would be interesting to place the second device on the same concrete pad to see if both get the spike at the same time, then maybe a short distance outside etc.

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Thx for your reply. Yapp I red some of the old replys but i could not see a simple solution. I have my shake just since a few days in operation and wonder of course if it is a fault in the unit (or its amplifier). Unfortunately the circuit layout is somehow not public. But there are some things we should try like:
Different Power supply’s, shortend/open input of the measurement channel, different location of the equipment, different raspberry pi boards. If the issue remains then it should be a faulty board… right? Since there are so many customer of this product I would be interested to know how many of them experience this? The amplifier is probably extremely sensitive and maybe there is something static charging up which then causes such behavior? The Shake HAT could be mounted remotely from the Raspberry just connected via RS232 maybe that could help as well?

BTW, is there somewhere documented for what the Connector K2 is good on an RS1d board? Maybe already an OOTB rs232 interface?

On the other side I could monitor in Europe the big Earthquake in Turkey without even a complex mounting of the shake (deep in the earth). The Shake is just standing in the basement on the floor … pretty impressive!

kr, --thomas

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I am convinced at this point that it is not a problem with the shake. As I said, I think it is expansion/contraction of (in my case) the concrete floor or maybe the metal walls/roof of the barn.

Watch it for a while, and I think you will see the frequency of these spikes increase as temperature swings are larger, and diminish when temperatures don’t change much between day and night - like here at the moment the temperatures vary from 40s (F) night to 50s (day) there are none of those spikes:

(The one at about 18:50 PST is me on my radio, running ~ 1Kw)

It will look quite different when the rain stops and there are big temperature swings.

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Japp that would be a good explanation if it’s linked to tension changes related to temperature changes. But on the other hand in our basement it’s the most stable temperature in the house… but I will keep an eye on it and also change the location… Its always an extremely short spike like a single sample which is out of the range and it looks always the same… if its liked to the surrounding there should be more variations… lets see … the time will show.

here a maximal zoom: spike with zoom

It also could be a driver issue were the values get red from the ADC and then get written to the storage… for example when I restart the raspi shake I have also a funny “swing in” as in the following picture: reboot_start_rs

those pattern are reproduce-able and similar … so they seem not to be related to real movements of the seismometer …

I am currently using a raspberry 2b.

The next time on the site I will change the deployment and see.

kr, --thomas

Hello R2D2, and welcome to our community!

As Philip has mentioned, spikes as the ones you are seeing every now and then have been noticed by many users in the past years, most being related to WiFi usage or RF interference signals.

Could you please take some pictures of the enclosure and the Shake inside it, and send them to us? Having them will help in providing more information on the general environment next to the instrument.

Thank you.

FWIW, I noted two this morning:

These are relatively small, I have see much larger ones.

Those look fairly sharp, and could, at first sight, resemble glitches in H/W or even S/W.
However, if you look at the data (dat.txt, below), you will see that it is not. It actually takes quite a few samples to drop to its lowest level (11564), and recovery is even slower.

dat.txt (3.7 KB)

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