Hello I am in need of a current monitor/sensor like INA219 for monitoring current in the range of 0.1 uA to ~ mA. Kindly suggest a way to monitor current in such lower range. I have a microcontroller and a Accelerometer. I need to monitor the current consumption over a time using a current monitor and Arduino.
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Current consumption over a time period suggests voltage-to-frequency or current-to-frequency conversion. Current spikes will be integrated into frequency over short time periods, while any microcontroller can collect frequency in its counter/timer. Count overflows can be extended to whatever lengths are needed in software.
The Texas Instruments application note AN240 suggests some circuits:
AN-240 Wide-Range Current-to-Frequency Converters (Rev. B)
For such low range of current measurements the best approches used are
1.Shunt Ammeter and 2.Feedback Ammeter.
Feedback ammeter are much more accurate than shunt ammeters.
In shunt ammeter the voltage burden (the drop caused by the shunt resistor) will not be considered.
where as in Feedback ammeter the voltage burden will also be taken in to consideration.
The accuracy and least count of the measurement is not only depends on the method - it depends on Amplifier design, cables used for measurement, ADC resolution and resistance tolerance.
You can get one of uCurrent clones. They are pretty good and one of the cheapest way to measure very low current with a simple multimeter.