Electronic – how do energy consumption (Ah, kWh) meters work

current measurementenergymeasurement

How do devices which measure energy consumed work? For example the ones in solar regulators/chargers which display how many Ah went into the battery and how many went out?

Do they just measure the current for example every second and a microprocessor constantly adds up the measurements, assuming that the current 0.5s before and after each measurement is the same as while they take the current measurement, or do they have a way of really measuring how much energy went through, without referring to such, possibly inaccurate approximation?

Best Answer

An MCU is not required to perform this sort of measurement. The STC3100 is a simple I2C interfaced coulomb counter that measures the charge state of a battery. It works by integrating the measured current into/out of the battery over time and providing the result in a form that can be read by the processor.

I have used this device on a couple of products and find the results better than I would have thought bearing in mind the large variations in the load current that can be seen, in my case the load current varies over at least 4 orders of magnitude. The errors due to the sampling of the varying current seem to cancel out over time.