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I have an embedded application that wakes up every 15 minutes and performs some specific function for a period of two minutes.

I need to log the current consumption of this specific function on the embedded board say for a period of two weeks and see if there was any unwanted current consumptions caused due to some unknown software cases.

I am thinking of buying a cheap NI DAQ. I would like to have some suggestion on how to go about this task.

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    \$\begingroup\$ "cheap NI DAQ"...I've never heard that phrase before... \$\endgroup\$ – The Photon Feb 15 '13 at 4:00
  • \$\begingroup\$ @ThePhoton USB-6008 is relatively inexpensive. \$\endgroup\$ – Nick Alexeev Feb 15 '13 at 4:11
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My initial presumption is that software cases that will lead to increased current consumption are those that result in subsystems being powered for longer than expected.

At a first-pass (and without needing any extra hardware) I would suggest that in firmware you log the amount of time that the processor is "awake". This will check that you are in fact only in full-speed mode for 2 minutes. The longer you spend in full-speed mode, the higher the average current draw.

Also look for peripherals whose power is controlled by your embedded system and log their on/off periods. Again, any logged event that is longer than an expected deviation may be indicative of a problem.

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The $30 Tekpower multimeter has an RS-232 interface and would do that with a laptop and the appropriate software. Connect it in series with your +5V (or 3.3V or whatever it's running on) and come back in two weeks.

Note that the meter does not send ASCII strings (which most any terminal program could save to a text file) but rather a packet of bytes representing the display, segment by segment. I use QtDMM but it may not have enough storage for two weeks worth of data. Some terminal programs may be able to collect and store binary data which you could post-process.

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New at it but i guess you must also have switched the CPU to Low power mode while its sleeping. Logging the time for peripherals on-off is a good idea, but you may have interrupts in between and timing may not be consistent always. You may need to take care of it.

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  • \$\begingroup\$ I think you may be misunderstanding the question. It is not about how to low power, it is about how to measure his current draw over time to see what the system is doing. this is an important part of auditing a design. \$\endgroup\$ – Kortuk Feb 24 '13 at 2:25

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