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Windows 7: Volts question

18 Jan 2019   #1
F22 Simpilot

Windows 7 Ultimate x64
Volts question

I have a true RMS multimeter. When I measure the voltage of a 12 volt AC adapter it comes out to be around 14 volts. Why is that?
My System SpecsSystem Spec
18 Jan 2019   #2

Windows 10 Pro x64 x3, Ubuntu

Most general purpose Power supplies AC Mains to DC (or rarely AC/AC), are designed to provide their rated output "On Load". [Connected to the device they are powering]

This makes them much easier and cheaper to produce than the type that would produce an accurately controlled output when open circuit Off load which is what you are testing using a multimeter. The output "floats" until it is connected to the load when it has some feedback and can accurately match the requirements of the application.

on a 12V DC I would expect to see around the 14V that you are seeing, but for accuracy you would really need to test under load Either a voltmeter reading across the input or maybe a current draw reading and a quick calc for a truly accurate reading
My System SpecsSystem Spec
18 Jan 2019   #3
F22 Simpilot

Windows 7 Ultimate x64

The adapter I have here is AC. As I mentioned it outputs 12 volts AC. I had to buy a 12 V AC adapter in lieu of a 12 volt DC adapter for my Ring doorbell. Don't know if Ring is a market in the UK, but it's essentially a doorbell with a camera.

I think I may test the voltage with it's draw and see what number I get this time.

I have an UNI T DMM which is also a clamp meter, and I made my own AC line splinter so I can test current.

Really is a great DMM despite it not being a Fluke version.
My System SpecsSystem Spec


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