Missing the Coulombcounter on the markers

I’m currently using version 0.6.8 due to the functionality of the markers. I’m a bit lazy, and measuring the coulombs between two markers was really useful for analyzing proposes. Is there a reason why this coulomb counter is removed in version 0.7? Currently i’m exporting the data between the dual markers and take the overall counted coulombs which lead to similar results, but this takes more time.

Thank you for reading!

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Hi @Groj

Wow, you are total right, and I confirm what you see. This computation must have been lost when we restructured the markers to prevent crashes in 0.7.0. I created issue #40 on GitHub:

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∆t is there, on the time axis between the markers. But yeah, it’d be great to have the charge consumption shown, preferably in mAh if possible :slight_smile:


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Hi @JuliaTruchsess - ∆t used to be displayed with all the other stats in addition to being up top. The value up top is not always easily legible, so I will plan on adding it back to the rest of the marker statistics. Once I have a way to cleanly display ∆t up top, I can get rid of it.

You will also be happy to see this:

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Just a curiosity question, I’m interrested in the way the Coulombs are calculated. Is it the integral of the current over the time. Or does the Joulescope use a coulomb-counter that measures the charge in (n/u)Ah?

Hi @Groj - Joulescopes are shunt ammeters, which is a fancy way of saying that they have a calibrated, precision resistor between IN+ and OUT+, measure the voltage across the resistor, and use Ohm’s law to calculate current. The Joulescope software then computes charge by integrating current over time. The existing implementation uses Euler integration, which is the sum of each sample times the sampling period. The software integrates in a sequence of small time chunks in single-precision floating point (soon to be double-precision) which then get combined into a 0.5 seconds window. That 0.5 second window then accumulates into an infinite precision integer in units of pC. This avoids any numerical instability/inaccuracy with floating point. If I didn’t answer your question or you want more detail, let me know!

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That is really precise! Also a clever way for floating point calculations.
Maybe it is irrelevant, but is there also a reference point used by shunt ammeters?

Thank you for the information!

Hi @Groj - To learn more about measuring current, I like my blog post :wink:

Lee Teschler drew upon a couple of my blog posts for his article in Test & Measurement Tips:

Wikipedia also has a decent summary:

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Thank you for the information! :smiley:

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Fixed in 0.8.x. Upgrade now!