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| IoT consumption logging/profiling |
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| Jorge:
Hey everyone! I'm searching for a device to measure power consumption of a custom IoT device that ranges from a few uA in sleep up to 2A peak during data tx. Already have a ucurrent gold for small burst profiles, but this has a lot of limitations with the burden voltage and the lack of long-term logging. The budget would be about 2kish, and for what I found my options are basically Joulescope or ZS1100A. Also found the power analyzer N6705C from Keysight, but it’s well over by budget. |O Any idea if there’s any like 5x cheaper N6705C alternative? :D Cheers. Jorge |
| thm_w:
--- Quote from: Jorge on March 25, 2022, 12:25:42 am ---Already have a ucurrent gold for small burst profiles, but this has a lot of limitations with the burden voltage and the lack of long-term logging. --- End quote --- You would use an appropriate external DMM for logging for that purpose. https://www.eevblog.com/forum/testgear/how-to-measure-energy-consumption-on-a-iot-sensor/ https://www.eevblog.com/forum/testgear/test-equipment-for-integrated-average-current-down-at-the-ua-level/ https://www.eevblog.com/forum/testgear/looking-for-good-and-fast-ua-meter/ https://www.eevblog.com/forum/testgear/power-integrating-multimeter/ https://www.eevblog.com/forum/testgear/equipment-advice-battery-lifetime-testing/ |
| Cerebus:
Another route is powering from a measurement power supply, like a HP/Aglient/Keysight Model 66312A "Dynamic Measurement DC Source System" which is basically a poor man's SMU (Source Measure Unit), or a fully fledged SMU from someone like HPAK or Keithley. I pick the 66312A just because I happen to have one. They turn up on the secondhand market from time to time at quite reasonable prices - usually around the £300 GBP region. It's a 0-20V, 0-2A bench power supply with more extensive, more precise, faster measurements than a typical bench PSU. It can measure at a resolution of 2.5uA on its low range (-20mA to +20mA) and 250uA on high range, and can switch measurement automatically between the two. Will store 4096 readings with a sampling rate range of 15.6us to 31,200s. Needs GPIB for fast readings, slow ones and the 4096 reading store can be read out on an RS232 port. It sounds like it might fit your requirements. If you need faster or finer resolution you're probably into a fully fledged SMU. Again, you might get lucky and find a secondhand one within your budget, but the Keithley ones usually change hands for a bit more than 2k, HPAK ones are like hen's teeth and I'm poorly informed on other brands. |
| hans:
--- Quote from: thm_w on March 25, 2022, 12:51:15 am --- --- Quote from: Jorge on March 25, 2022, 12:25:42 am ---Already have a ucurrent gold for small burst profiles, but this has a lot of limitations with the burden voltage and the lack of long-term logging. --- End quote --- You would use an appropriate external DMM for logging for that purpose. https://www.eevblog.com/forum/testgear/how-to-measure-energy-consumption-on-a-iot-sensor/ https://www.eevblog.com/forum/testgear/test-equipment-for-integrated-average-current-down-at-the-ua-level/ https://www.eevblog.com/forum/testgear/looking-for-good-and-fast-ua-meter/ https://www.eevblog.com/forum/testgear/power-integrating-multimeter/ https://www.eevblog.com/forum/testgear/equipment-advice-battery-lifetime-testing/ --- End quote --- DMM's have two issues. uA to A is a dynamic range of 6 orders of magnitude (120dB, 20-bit). This is not out of the ordinary for 6,5 dig or more DMMs, but then the 2nd issue pops up: usually those devices only reach a high measurement resolution with multiple line cycles. For an IoT product the current profile can be rapidly switching, therefore also requiring ksps sampling rate. In the past I've made custom measurement devices for these kinds of things. Basically put two current ranges side by side. Let the uA clip once the A 'needle' is finally moving off center. With 2 channels you don't need 20-bit accuracy but can get away with e.g. 14 or 16-bit. If purchasing off the shelf.. I'm afraid either make a compromise on resolution/accuracy or sampling rate, or price. E.g. normally I would recommend the Nordic Power Profiler, but that doesn't go up to 2A. |
| Jorge:
A DMM could be kinda slow (a few ksps). On our use case where the narrow current spikes will make a hell of a difference on a 3-to-5-year battery life span, and I’m afraid of the slow data sampling. Those R&S with 500ksps seems okish, of course it’s an awesome DMM, but I need it for the data logging. |
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