Again, thanks for everyone's comments. I'm pretty sure this is just a terminology thing on my part.
If your DC voltage is changing up and down in a cyclic way you can understand this voltage as a sum of two components: a pure DC bias component and an AC component superimposed on top of it. Your multimeter and AC coupled oscilloscope are able to remove the DC bias component and show just the AC component which remains.
So your supply "switches between" (aka. "alternates") between 2 and 3 volts.
And then you ask why you are measuring "Alternating Current"?
You are measuring AC because you are generating AC.
Yes, I asked why I'm measuring "Alternating Current" because as far as I know the current never actually alternated or reversed its polarity.
The current still flowed in one direction, just at different amplitudes.
Here is another example but simpler than my previous one...
Place a 1.5 volt AA battery with a 100 ohm resistor and you get .015 amps of DC current.
Add another AA battery in series and we now have 3 volts and .03 amps of DC current.
Take one battery away and we are back to .015 amps.
My little brain tells me by removing the battery we simply reduced the voltage and current. The current never reversed or alternated its flow inside the wire. Or did it? If so can somebody please explain?
Cheers
Mark
The multimeter doesn't care!------If the
dc voltage goes on & off.or if you could switch very quickly between your one battery & two batteries in series,the meter will quite happily see it as
ac.
All it cares about is that there is a
change in voltage ----it will see the difference between the two voltage levels.
In fact,if you connect your meter,set to
ac volts,across a battery,at the instant you make the connection,the meter will attempt to give you a reading of that sudden change.
You can make a simple
ac volt meter by connecting a diode in series with one of the meter leads of a
dc volt meter.
You then only measure the average amplitude of the 1/2 cycle during which the diode is conducting.
DON"T DO THIS WITH THE MAINS!-------the chances of
killing yourself,blowing up your meter or your diode are high!
"Half-wave rectifiers" as described above, tend to give some errors which can be resolved by using a "Full wave rectifier".
This causes each consecutive cycle to be in the same polarity,so a
dc meter can read the average of the amplitude of all half cycles.
This can be,(& is,in practical devices),converted to read in RMS volts------but more on that later.
This is how analog multimeters read
ac,but the rectification is done inside the meter.
I'm not a DMM guru,but as far as I know the same thing is done in them.
You could measure both 1/2 cycles individually,then combine the results with software,but that means your Analog to Digital Converter (ADC)would have to have a greater dynamic range.(maybe this is done in some meters).