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In general, power supplies should output pretty much exactly the voltage that they claim; in reality there will always be a tolerance, typically 5% or better and you'll see this in the datasheet for the device.  On high-current supplies you'll sometimes see 'sense' inputs; the purpose of these is that they can be connected to the point of load so the supply can adjust the output to make sure the load sees exactly the right voltage.

Incidentally, vehicle electrics are 13.8 because that's the normal charging voltage a 6-cell lead-acid battery.  The idea that it's 2v per cell (12v total) is an approximation and depends on the load and state of charge (etc).  You may see bench supplies designed to drive automotive equipment such as radio transceivers that specify a 13.8v output.
Repair / Re: Part identification help :)
« Last post by kalinga on Today at 03:06:41 PM »
Hey dave,

i was thinking the same, thanks!
Test Equipment / Anyone else own a Z-TEST troubleshooter?
« Last post by dorkshoei on Today at 03:05:24 PM »
Curious if anyone else owns one of these?  Made by a Canadian company called Z-Test.   It was released in the US under the Fluke brand but in Canada under the Z-Test brand in the early 1990s.   Basically a more advanced version of the BK Precision 860 out-of-circuit/in-circuit tester.   

I have one of the Z-Test TM3000 versions.   Supposedly there were later TM-3028 and TM-3064 versions but the only information I can find on these two later versions is a scanned service manual.     Z-Test are nominally still in business, but doing something totally different.  Their reply when asked for help was pretty much; we're glad to hear you're using this 20yo old stuff, now please go away ;-)

Curious if anyone has more info on these later 3028/3064 models,  or even owns one.

IF ANYONE HAS ANY PARTS I'D LOVE TO HEAR FROM YOU (please private message me).  I'm looking for the Interface Buffer (approx 8"x8"x1" sized box) that plugs into the side of the main unit.   Until I can find one,  the main unit (pictured below) is basically just a doorstop.

No, we don't "know".

Some usb chargers have sense wire all the way to connector so that output will be 5v no matter the load
Others will just use a 5.6v zener diode as voltage reference

Car stuff is more like "whatever battery or alternator gives" with additional allowances for spikes or reverse voltage periods ... auto power is just ugly.

if you mean atx power suply voltages they're standardized , just read the atx specification, it's available on the net a site with "form factors" or something like that in name has it
I got the chrome plated steel version; it's holding up well so far.  (Granted it's in a dry location)  To make the shelves more 'small part' friendly, I cut 2 x 4 foot sheets of 1/8" thick tempered hardboard to fit; that gives a nice smooth surface and is well supported by the fairly dense wire beneath it.

It sounds like buying real shelves makes sense.
I`m looking most quiet / low ripple switching power supply architecture to power up my lab: signal generator, bench multimeters and other projects.
Can anybody help me with proper guidelines and/or design manuals?

Beginners / Re: Change a Dc power supply for an AC power supply?
« Last post by Brumby on Today at 03:01:16 PM »
To make things very simple - AC is just DC that changes over time (in a cyclical manner).

Purely resistive circuits are easy.  They can be analysed at any point in time with a DC input at that point in time.

When the input is steady DC, then that analysis will apply at all times.
When the input is AC, then the analysis will be the collection of (an infinite number of) DC points where each DC point is defined as the input at a specific moment in time.
Projects, Designs, and Technical Stuff / Standard power supply voltage
« Last post by 001 on Today at 02:56:57 PM »
We know that common USB charger voltage is not 5.00000 volts but 5.1-5.3 to compensate wire loss
And automotive radio PS marked '12V' in fact about 13.8V for same reason

What about 'real' voltage for 3.3/9/15/24 volts power supply?
Beginners / Re: output from transformer is coming not as expected
« Last post by Brumby on Today at 02:51:18 PM »
That circuit is very basic.  Since you want to parallel two of these, there are more things to consider.

Personally, I would take a different approach - but rather than muddy the waters with my thoughts, I will defer to those who have had more experience in building custom power supplies.
by tweaking 32h. as fine adjustment as it gets. Adjusting 33h makes voltage jump.

It suggest that calibration data are parity and checksum encoded, and such tweaking will leads to oblivion unless you decode the encoding.
It wouldn't be just poking the bytes.
There is no checksum. And CAL works fine.

I was hoping that this brand of instrument is somewhat reputed, though not in the same rank and file with names like Agilent, Tektronix or even fluke... but to imagine that the programmer did not checksum or parity encode the calibration data for integrity checking before starting up is somewhat insane, so to speak.... if that's true, then we should drop the brand by mere reason that it is startup unsafe. Furthermore the ripple voltage is as huge as like the elephant boogies.. |O
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