Electronics > Beginners
How to measure average power use over time for small fluctuating circuit?
mzzj:
--- Quote from: ogden on September 23, 2018, 05:39:10 pm ---If we assume that 0.1V drop is tolerable during 1ms spike @0.4A:
(0.4Amp * 0.001sec)/0.1Volts = 0.004 farads = 4000 uF. No need for supercapacitor.
--- End quote ---
You get rid of voltage ripple but still have "somewhat big" peaks on current measurement depending on your shunt resistor value.
OP's needs or scope shots are bit open to interpretation but guessing from the scope shot he has 1ms peak every 1 second?
4000uF cap with 1ohm shunt would reduce 400mA 1ms peak alone to ~90mA peak over the ~0.4mA average.
ziplock9000:
--- Quote from: imo on September 23, 2018, 06:07:37 pm ---The OP wants to measure over several minutes, afaik. Also, he/she is using a few "electrically moving parts", maybe servos. Therefore 2A peaks are possible..
--- End quote ---
The most demanding part is a WIFI module. As stated earlier, the largest peak is 300-400mA.
ogden:
--- Quote from: ziplock9000 on September 23, 2018, 08:21:41 pm ---The most demanding part is a WIFI module. As stated earlier, the largest peak is 300-400mA.
--- End quote ---
Hey, when instead of chatting you will solder capacitor on your device input terminals and actually try something? :D
David Hess:
My better handheld multimeter has a minimum, maximum, and averaging function which can make these measurements over arbitrarily long times. A multimeter with averaging would be perfect for this.
ziplock9000:
I imagine they do this digitally by taking samples as mentioned in my OP. I'm going to make an assumption here that the sample rate is going to be at least 2 order of magnitude too slow for my use (which isn't really that high speed anyway) of around 1 to 10x second whereas I need at least 1ms. For example all of my DMM, bench and mobile are WAAYY off and don't catch the MAX spikes or even the MINS that are much longer in duration.
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