One of the things you asked us for after launching the new Power Profiler Kit II (PPK2) was extending the maximum logging time, some of you wanted hours or even days of continuous logging. We went to work and have now released an update for the nRF Connect for Desktop Power Profiler app, so the upper limit is now raised to a staggering 500 days of continuous logging. Below you can watch a video showcasing the new features we included in the app with this update.
The video mentions how lowering the resolution of the logging does not affect the accuracy of the readings. This is because when you select a lower resolution, you’re not *actually* changing the sampling frequency of the Power Profiler Kit II. The logging always runs at the base frequency of 100.000 samples per second, and when a lower resolution is selected the output is based on the average value for the chosen period. This saves space in the memory buffer and allows the PPK2 to log data for up to 500 days before hitting the buffer limit, when using lowest resolution of 1 sample per second. The table below gives an overview over the maximum logging time for each resolution when using the PPK2.
432 seconds (7 minutes and 12 seconds)
As you can see the maximum available logging time is dependent on what your selected resolution is, so you’re able to choose the resolution and length that best suits your needs. For the original PPK the base sampling frequency is lower, so the values for this change correspondingly.
Another neat feature introduced with this update is that the trigger function now also works in the PPK2. This allows you to set it up so logging of a short window automatically starts when a set rising-edge current limit threshold is met, much like the way oscilloscopes do. The window length is adjustable from 5.85 ms to 52 ms and you have the option to freely select where in that period the trigger point happens. This enables you to look at what happens both before and after your trigger point, or just on a single side of it if you’re so inclined. Due to its bandwidth limitation the original PPK does not have the same pre-trigger frequency as it’s max sampling frequency, so for that kit you’re only able to log values starting after the actual trigger event. This bandwidth limitation also makes the maximum sampling length with the full resolution less for the original PPK than the PPK2.
Both the PPK and the PPK2 support both the single trigger, and the continuous trigger mode, where the trigger keeps capturing a new window of the set length each time the trigger limit is met. If you stop it manually the values from the last of the triggers are retained on screen and can be examined further and exported or saved. Either as a CSV format for processing in Excel, MATLAB or with Python, or in the new .PPK format that can be opened in the Power Profiler app so it looks just like it did when measuring or get a screen capture of the plot with the click of a button directly in the app. To reload saved .PPK files back into the app, you first have to disconnect your device, then you can select “Load” with the button right below the “Select device” button.
We also made improvements to the digital channels, so you’re now able to show the digital inputs for windows of up to 30 seconds of length, that’s 10 times more than the previous 3 seconds. The function is as before available together along with the data logger and syncs up with it so you easily can relate what’s happening on your digital pins to the power draw of the device under test. When using the data averaging, the digital pins will also be averaged. This means that you will still see if something has happened during a certain sampling period.
If you don’t have a PPK2 yet, find out where you can get one by clicking on this link. If you already have a PPK2, check out the get started guide to get your kit up and running. And remember the most important thing of it all: have fun with your PPK2!
PPkit2 is a game-changer. There are only a handful of DC power analyzers and the most expensive(~700$) although spec is better. PPK2 is good enough for low power applications. especially single cell battery…
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Is the constraint for the "Maximum time" a capture can run the amount of RAM on the host PC? Or is it due to a constraint in the PPK2 hardware itself?
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