Am I reading my multimeter wrong

[Bishop Vogue]

Had a happy accident recently when I grabbed a spare Boss 9v adapter, plugged in my nothing special, DIY NPN Fuzzface pedal, and it roared to life.  My first thought was that my battery must have been half dead for it to go from just OK to amazing just by changing from battery to adapter.  But I measured the battery and it was full.  Next logical step: measure the adapter.  So I hooked it up to my multimeter and ...WTF?  I know there are plenty of people here who really, really know their stuff, so I thought I would put it out there: how can this adapter measure almost 16 v when it says 9v on the label.  Images below...

[wavley]

The ACA is an unregulated adapter so it will read just as you have it without a load.

http://www.bossarea.com/other/aca.asp

[mcknib]

Can't see your images but the output difference depends whether it's a regulated power supply

From wiki:

A regulated power supply is one that maintains constant output voltage or current despite variations in load current or input voltage. Conversely, the output of an unregulated power supply can change significantly when its input voltage or load current changes.

Most Boss adaptors will be regulated yours must be unregulated

I've only ever had about 9.4v out of my regulated boss adaptors.

[armdnrdy]

The ACA is an unregulated adapter so it will read just as you have it without a load.

#1

As R.G. has pointed out in several threads, AC/DC wall adapters are rated (guaranteed) to at least output the voltage listed at the current listed. In this case It will output 9 volts up to 200 milliamps.
Higher than 200ma.....the voltage will drop below 9 volts.

[MrStab]

definitely not the case here, but for future reference, dead batteries in the multimeter can produce too-high voltage readings. that happened to me just earlier, with 9V reading 18 or so. i knew what the problem was, but unscrewing the 3 screws on the back was too much effort i care about the environment and i wanted to drain every last drop of that battery.

[PRR]

Note that the label says *input* is supposed to be _100V_.

If you plug that to North American 110-125V wall-outlets, the full-load output must be 10%-25% high.

On top of that, an un-regulated wart will un-sag 5%-40% when checked no-load.

Taking the extremes: 9V * 125% * 140% = 15.75V on a nominal 100V-9V wart. Which is within 1% of what you are seeing.

How do you have a 100V (Japan-only) wart? Maybe BOSS makes these so good they survive 125V wall outlets, or maybe you got it on your last Tokyo Tour and should not have brought it back to the land of 120V.

[armdnrdy]

Maybe you need a transformer for your transformer! 

[Bishop Vogue]

PRR... I think you nailed it.  I did get this while working in Japan!