Electronics > Metrology

Siglent SDM3055 comparison

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I don't think Andreas was having a go at you or anything, it's just very common that meters aren't adjusted when they go for calibration.  ^-^

It sounds like your 3457A was adjusted to be right on the money, does the report state the uncertainties of the references? Usually they only tell you the equipment used, it's only when you get an accredited calibration that you get all the uncertainty data. This is all a biiit unnecessary but we are volt nuts after all, I just like seeing uncertainty data, no matter how big or small.

Just throwing it out there, I think my 3457A has never been adjusted and it reads roughly 20ppm high on 30V range, reference is about 4ppm uncertainty(95%).  :P

I'll post some data from the report when I get home tonight.


--- Quote from: mojoe on February 23, 2016, 06:36:45 am ---If you are (or think you are) an expert, take this into account and don't jump down my throat

--- End quote ---

I do not regard myself being a expert.
And it is not my intention to go at your throat.
I am just curious (and asking a lot).
From the first post I did not recognize that the instrument has been adjusted/calibration data was lost.

But also if it has been just adjusted it is no guarantee that the reading after adjustment is perfectly spot on.
E.g. through noise or other effects as you can see in the thread of Dr. Frank from his 34465A.

I also still have to learn as most of us.
E.g. I did not expect that you can adjust a instrument just by changing orientation.
The big question is: where is this specced in the data sheet?

Most LM399 based instruments are affected, some more some less.
The HP34401A has its largest change between placing on the back side and the front side down.
The Keithley on left and right side. (As in the photo).

With best regards


I didn't have time to post it last night, but here is some data from the 5-page report I got back with my meter. Make of it what you will.


--- Quote from: mojoe on February 23, 2016, 02:29:43 am ---(asumming the 3457A is dead on)

--- End quote ---

That is a rational preliminary assumption. Who would assume that one of the two 5.5 digit meters showing different values (and I assume with no recent calibration) would be more accurate than a newly calibrated 6.5 digit meter.

Of course, even if the calibration included adjustment, the meter might not be spot on for several reasons originating in calibration laboratory, transportation trauma, environmental change, intermittent instrument error or whatever.

That is not the point. The point is that - in lack of more information - your best estimate for an accurate volt reading is the newly calibrated 6.5 digit meter. And you rationally assume - until you gain suspicion, indications, evidence, 'proof' or you-name-it contrary to this assumption - that the meter is spot on.

Assuming, with no reason to do so, that the meter is 4.5 ppm low or 7 microvolt high when you receive it from calibration would imo be somewhat special.


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