testing the geoduinos

[jerabaul29]

@jvoermans with reference to #21 .

Do you think it would be possible to test the geoduinos? I.e. for example put the logger on a table at rest, connect all the geoduinos as would be expected, and hitting the table with a hammer at the opposite side of the table, varying the strength of the hammer hits? This would allow to test the full chain software + hardware, and to have a look at how this kind of "model signals" look like.

[jvoermans]

Yes I can do next week :)

[jerabaul29]

Perfect :) Yes, good to keep the issue opened as long as not this has been tested, so that we do not forget :)

[jvoermans]

@jerabaul29 Finally time to test the geophones, see data here: https://github.com/jvoermans/Vibration_Logger/tree/master/material_Jean/BinarySdDataParser/all_example_data/example_data_geophone_temperature

It includes 4 temperature probes (temperatures are not the same due to the sun). I amplified the signal of the z-coordinate in 3 ways (gain of 5, 10 and 200), so you'll see one excessively large signal.

This leaves just the pressure probe, wind anemometer and sonar. I compared temperature probes, the difference between them is within the specified accuracy. However, pressure probe shows quite some differences. I have to see why did is (it is originally not designed for atmospheric pressure)...

[jerabaul29]

Perfect, that looks very good I think @jvoermans :)

• interesting geophone signal. Were you performing some form of pseudo periodic forcing or other to get such a well defined frequency in the data? How did you generate the motion that was logged?

• Yes, agree, it looks like the temperature probes are perfectly well read and parsed.

• Ok, maybe you should consider using an atmospheric pressure probe. Which one were you using so far? The bluerobotics pressure probes are thought for measuring depth, and will have a range completely different from what is needed in atmosphere (in atmosphere a probe should have a range 970-1050 hPa or something like this, for a ROV rather 0 to 10 atm). If you want to measure atmospheric pressure, wonder if you should rather use something like this:

https://www.adafruit.com/product/3966

and a wind sensor in this kind may be enough?

https://www.adafruit.com/product/1733

[jvoermans]

The frequency should correspond to the natural frequency of the bench I would say, which dampens in time.

Regarding the atmospheric pressure, I've been looking for a decently priced one for a while, but one that is robust in extreme environments is hard to get. The adafruit one is possible, but need some epoxy to protect it. This is a pain. I think the blue-electronics one has quite a high accuracy, it just hasn't been calibrated for that range (i.e. atmospheric pressure is basically just a reference for them).

I already have a wind sensor, got the Davis Anemometer. Reviews seem to suggest that this one is a bit sturdier in very cold environments :)

[jerabaul29]

That sounds reasonable, this is what I would have guessed but good to get confirmation :)

Ok, sounds good! I think for the pressure sensor that the simplest would be to have it in a small box on top of the logger, and make a few holes at the bottom of the small box, in such a way that when the whole thing is in the right upwards position, falling water / snow will not fall inside the box onto the pressure sensor. That should be enough to protect against direct water exposition. This way, should be ok to have it outside (at least reasonable to test :) ).

[jvoermans]

Yes, I thought about that. FirstI thought you can just put it in the pelican, as it has a pressure valve so should be reasonably close to atm pressure. Issue is heating, whole box needs to be protected from the sun. Though I'm sure can make the box small... Also not how it works with condensation.

[jerabaul29]

Testing will tell :) I think that pressure measurements should not be negatively influenced by temperature. I am more worried that the pressure valve may have a quite high hysteresis / that it requests quite a bit of pressure difference to open it. So would be more in favor of an additional small box with holes.

[jvoermans]

That is true. Perhaps put them in the freezer overnight to see how that goes!

I'll look at a simple 1 dollar light sensor as well. Should be possible to 'epoxy' that in the lid of the pelican. Should give an idea whether there is snow on the case or not.

Another question related to this, if there would be water damage to one of the sensors, do you know how this will impact the instrument? i.e., will it just give error values for the sensor, or will it break down the logger?

[jerabaul29]

I think that would be a good idea.

That's an excellent idea with the snow measuring light sensor.

I hope that, as long as the damage is not too catastrophic, it should "just" give bad measurement. There is a risk that there may be a short circuit if the sensor is very damaged, but I think this should be quite unlikely.

[jerabaul29]

A possibility would be to put the "risky sensors" on some small transistors to switch them on / off, in case they fail we can just disconnect them.