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Record voltage across current-sensing resistor

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davekeck:
Hey all, I'm designing a PCB and would like to measure its charge consumption by integrating the current through a current-sensing resistor.

I assumed there'd be some pre-existing solution to record the voltage across a current-sensing resistor at a high rate, but I can't seem to find anything.

What would you use to sample+record the voltage across a current-sensing resistor at a high rate (khz-mhz) for a few seconds?

KaneTW:
Integrator with a suitable time constant.

EEEnthusiast:
It depends on what dynamic range you are looking to measure and at what speed. If the dynamic range is not large, then a scope with differential probe will do the trick. Use the uCurrent by Dave for the I to V conversion and feed the signal to a DSO. DSO can store the waveform for many seconds.

For high dynamic range, use a DMM with Digitizer option. Or a dedicated power profiler tool.

David Hess:

--- Quote from: davekeck on February 03, 2020, 02:14:51 pm ---What would you use to sample+record the voltage across a current-sensing resistor at a high rate (khz-mhz) for a few seconds?
--- End quote ---

I would integrate it in the analog domain with a single operational amplifier.  But as EEEnthusiast points out, many DSOs have an integrate function which can do it.

sam[PS]:
What about using a high side or cheaper low side curent sensor IC ? Some can be found pretty cheap these days (probably cheaper than a home made circuit) and they can be found in I2C or SPI output flavor, just slap any MCU there to record the data. It should be good up to few kHz region, just check the datasheets to be sure.

Now if you want to be up to the MHz region then that's another story, we are talking about a not so easy analog front end, a pretty serious ADC probably JEDC204B interface and a decent FPGA to manage it. That's probably much more complex than the remaining of the PCB you want to monitor. Plus if you are monitoring the board power supply, you probably have loads of decoupling capacitor there that limit the bandwidth anyway so i don't see the point in this.

Just my 2cts...

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