Comparing SAR to SINC performance using ADIMonitor

Document created by Jens Employee on Jul 15, 2013
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When you want to monitor variables you need to get the address from the IAR map file and Copy&past it into “Var Address” field. The table below summarizes the variables representing current measurements:Capture.JPG

 

 

 

 

There are two groups of signals – raw, unscaled signals and scaled signals (green). When comparing sigma-delta to SAR it is best to use the scaled version as it makes the signals directly comparable. That is not the case with the raw data. Furthermore the scaled version is floating point and uses Ampere as unit (easier to relate to).

 

To compare current measurment performance it is recommended to monitoring signals marked with green – for example ia_sar and ia_sinc. Both of these are single precision float so you need to specify 2*4bytes=8 buffers in “Buffer Setup”

 

Always click corresponding "Update" bottom when making changes to ADIMonitor settings. Though not required, it is a good idea to stop plot refresh when making changes.

 

To display 2 signals in the same plot, specify same number in “Plot#”. For example “1” next to both signals. To uses two different plots specify different numbers in “Plot#”. For example “1” and “2”. Again, remember to click update.

 

When done ADIMonitor should look something like this:

ADIMonitor.png

 

And the resulting plot should look like this:

plot.png

Top plot shows the result with LEM sensor+amplifier+SAR ADC.

Bottom plot shows result with Sigma-Delta converter+SINC demodulation.

Data are sampled at 10kHz and with 200 samples per plot; time range is 200/10000=20ms.

Y-axis show true current in ampere. Full scale currents are 2*6.8A=13.6A

Inverter was switching at 50% duty-cycle while data were obtained.

 

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