[collectd] Averaging Samples when SigRok provides higher resolution

Kieran Bingham kieranbingham at gmail.com
Thu Sep 26 15:45:26 CEST 2013

Hi Bert,

On 25 September 2013 15:51, Bert Vermeulen <bert at biot.com> wrote:

>> For example, I have implemented a patch to do this at :
> https://github.com/kbingham/collectd/commit/47acd32d7a83538b74ec4d186af4891404f6ec08
>> Is this something that is worth adding ?
>> What are peoples initial thoughts, reviews, and reactions?
> This suggestion has come up before, but I disagree with it.
> - While you certainly do lose resolution by dropping measurements, averaging
> doesn't really get you that resolution back. Any transient spikes that get
> lost by measurement drops won't show up properly by averaging it all
> together, either.

We are looking at sampling windows of between 5 and 10 seconds.
Without some sort of enhancement, this means we are using 5 to 10
sampling points instead of 25 to 50.

I agree that averaging will not show any transient peaks/troughs but
it does at least bring those sampling points back into the equation.

Ideally - it would be better if I could dispatch all of the "min/max/avg" to RRD
for each period. But I'm not sure if thats easily possible with the
current framework.

> - The fact that you need to set MinimumInterval to 1 second because that's
> as low as RRD goes, and that this is not good enough, just shows that RRD is
> not the right tool for this particular job.

Indeed - its hard to disagree with that - but I'm not aware of any other tool
that will do what RRD does as well as it does it ... or anything better ...

is there anything you know of that could act as a stand in replacement?

Ultimately - we just want to be able to record and graph/visualise the data
points that we are taking.

We are looking at sampling windows of about 5 to 10 seconds per test,
so we don't really want to lose the resolution of the multimeter.



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