Voltlog #211 - Joulescope DC Energy Analyzer Review & Teardown

[johnlsenchak]

Voltlog #211 - Joulescope DC Energy Analyzer Review & Teardown
VoltLog
Published on Feb 25, 2019
The Joulescope is a low cost precision dc energy analyser which is currently on kickstarter so check the links below.



Posted  02/26/2019   Duplicate Post   turned  it into a new post  Sorry for the mistake

[David Hess]

Precision but no accuracy or noise specifications?

[coppice]

Precision but no accuracy or noise specifications?

I don't think they have specified the noise performance, but the accuracy is shown in both the above video and the manual.

[coppice]

There is a real need for a good tool of this type when developing ULP applications, but this one seems to have serious limitations that limit its value. The endlessly changing supply impedance is going to be really troublesome in a lot of designs, and the sampling is too slow to follow the true consumption of interrupt routines that only last for 1 or 2 microseconds of high consumption out of sleep mode. These are the kinds of limitations which lead TI to develop their MSP430/MSP432 tools, which feed metered shots of energy into the power supply. This gives poor accuracy in seeing exactly when the current demand goes up and down, but it solves the dynamic range issues in measuring the consumed energy with decent precision.

[splin]

It would be interesting to know what the ADCs, U22 and U26, are. I had a quick look on Digikey but the closest parts in 6 pin packages I could find are 12 bit 3MSPS parts. I wonder why there are two - interleaved perhaps?

[voltlog]

Perhaps one ADC for current and the other for voltage measurement?

[splin]

Perhaps one ADC for current and the other for voltage measurement?

Of course - I'd forgotten that it monitors voltage as well.

Are there are any markings on U22 and U26? Knowing which ADCs are used allow us to get an idea of the noise performance, which is rather important but unspecified.

[johnlsenchak]

Thanks for  joining  us here for this discussion 

[CChin254]

The ADCs used are the ADS7056 from Texas Instruments. It is chip number 10 listed in the image below.