Voltage not matching

[bdunham7]

Here accuracy of DVM is not enough to verify accuracy of source. End of the story, full stop.

True, but you've missed the point entirely.  He doesn't need to measure the source to within its specified accuracy to know that it is out of spec.  Confirming something is defective is often different than verifying that it is operational as specified.

[dietert1]

As far as i understand that power supply has built in meters. Do those indicate a similar voltage mismatch? Of course there is a certain risk that they used the built-in meters for calibration - who knows.

Regards, Dieter

[The Soulman]

Jan, I could send you a calibrated 7805 in the mail, I can measure it to about 0,01% uncertainty at the moment.
The 7805 will likely drift more from transportation and temperature changes but still be good enough to discern 4,900 Volt from 5,000.
Send me a pm If you think it will be useful.

[Jan Audio]

Thank you very much.
I attatched the cables straight into the DMM and it was exact correct, I feel very stupid now.
I dont know how i got the 4,9 volt ?, maybe a cable or aligator-clip problem in my project.

[Jan Audio]

Jan, I could send you a calibrated 7805 in the mail, I can measure it to about 0,01% uncertainty at the moment.

So you bought 100 pieces and measured them all on a very good meter ?
Nice one.

[Jan Audio]

So funny they calibrate gear with a agilent 34461A meter,
I almost was thinking i need it, the volt-nuts-disease is real.

[Jan Audio]

As far as i understand that power supply has built in meters.

Yes this is weird, i forgot to ask.
If i dial in 5 volt, the internal-meter says not exact 5,0000 volt.
So the meter is not changing the voltage, i thought that was how a switching power supply works, it measures and switches.

[wraper]

Thank you very much.
I attatched the cables straight into the DMM and it was exact correct, I feel very stupid now.
I dont know how i got the 4,9 volt ?, maybe a cable or aligator-clip problem in my project.

And how were they attached if not straight?

[Jan Audio]

Now with 1 cable.

[The Soulman]

Jan, I could send you a calibrated 7805 in the mail, I can measure it to about 0,01% uncertainty at the moment.

So you bought 100 pieces and measured them all on a very good meter ?
Nice one.

No, it means I can measure the output of a random 7805 fairly accurately and can give you that number such as 5,1234V  and if
you remeasure that same 7805 with your aneng meter and it reads for instance 5,120V we can be fairly certain your aneng is operating in spec.

But I believe your issues are already solved?

...the volt-nuts-disease is real.

Yes very real, I've started with two 2000 count dmm's that were a few counts apart (both well within spec) but my ocd
couldn't handle it so also got a 30.000 count bench dmm and a 10V vref, life was good for a while until a 20.000 count
bench dmm arrived, that was also just a few counts out compared to the other and the vref, but I couldn't be certain If either of them was 100% correct. 
So a few years and several external calibration rounds later I have one(!) 2.000.000 count bench dmm and 9 vrefs and various thermal sensors/probes with data logging etc. etc...

Still use those same 2000 count meters tho, lol.

[Jan Audio]

LoL, i googled OCD.