My 1AA battery sensor

[m26872]

@klim If you press the yellow button you'll see 1mAac. It will not imply real power, but impair battery life, Question is how much?

[klim]

@m26872: Why should i measure a dc current in ac mode? I did it anyway, the result was 0.87mA when sleeping. Please enlighten me.

[tbowmo]

@klim

As the stepup converter functions, by chopping the supply up with a squarewave (in the order of 100-400kHz) it will not be a dc current. It will be more like an AC current

see comment below.

[klim]

Thanks a lot for clarifying, i didn't thought about that before. This means the power consumption is not as good as it seems.

[tbowmo]

Tried to search google to back up my theory, but I failed at it :sa:

So I turned to a group of fellow electronic nerds, asking them how to measure things.. The conclusion from their responses is:

Use DC current measurement, if your multimeter is good at averaging things. Otherwise, use a oscilloscope with a series resistor, and use integral maths to calculate the real current usage..

So I was wrong in my assumptions.. Sorry :)

[klim]

Thanks for your info. That was my toughts too, to use an oscilloscope and integrating the current over time, but first i need a good digital oscilloscope to do that.

[therik]

This was also my method (using an oscilloscope to integrate the current), but...I found it difficult to measure the very low currents...µA range with an oscilloscope (these are very high quality Tectronics units, we have many at work, but there is some DC offset even though I calibrated the probe, yada yada yada). So, on some more recent measurements I used a Keithley bench multimeter with averaging. I guess the final test is to see how long the batteries (or battery) actually last.

[klim]

I know about the problems and accuracy for very low current measurements without special instruments. Therefore i want to buy a µCurrent Gold adapter soon, it is a very cost effective way to measure very low currents. This adapter with the combination of a digital oscilloscope with math is what we need here. But at the end as therik already said: the final test is to see how long the battery actually last

[tbowmo]

@klim said:

the final test is to see how long the battery actually last

Only problem is, that this is going to take a very long time to check..

[klim]

That's the reason, we must use instruments and methods to give predictions, instead of waiting for real results ;-)

[therik]

The longer it takes to find out, the better, right? ;)

[RJ_Make]

@therik Yes, but then any corrections also take longer to test.. :-)

[that0n3guy]

Well, if its pulling ~1mA, then it should only last about a month or two. (right?)

You could also pull battery voltages to see the battery "level" as well.

[Totche]

@klim Nice integration.

Do you have a schematic of your board ?
especially for the pins with the jumper.

As I can see, the blue jumper is for open/closed current loop, but for the other pins ?

Thanks

[jsiddall]

Looks like it has been a year or two now. Is it still going on the original battery?