Electronics > Metrology

Prema 6048 teardown

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dietert1:
Please don't adjust any of your precision devices, but do everything on paper. Without notes it's easy to get lost. Some people use a lab notebook to keep important information like that in a safe place.

You could just measure the Fluke reference as good as possible and note down the result, maybe together with ambient temperature. After the P6048 mod you could repeat the exact same procedure and determine the new value. This way you can always calculate "unmodded", calibrated results by subtracting the shift caused by the mod. It's easier to revert the mod as long as you don't adjust the Prema calibration.

Regards, Dieter

Rax:

--- Quote from: dietert1 on November 14, 2023, 03:59:30 pm ---It's easier to revert the mod as long as you don't adjust the Prema calibration.
Regards, Dieter

--- End quote ---

Dieter - thank you for your points, and no! I wasn't planning to touch the Prema calibration in any way. Not even close!

The only one I was considering adjusting is the 731B (to match the Prema at 10V), which, as much as it has unusually good tempco, it's a transfer standard, so literally designed for this purpose.

That said, your recommendation makes sense.

Rax:
I finally got tonight to replacing U9 and U10 with OPA 189. I'm getting "Error 1," which doesn't let me go any further (other than, when trying to null the instrument, "Error 4").

Any thoughts?

branadic:
Is this with something connected at the input? If not, that message is not surprising:


--- Quote ---OVERFLOW INDICATION ... ERROR1 in the main display
--- End quote ---
page  2/7


--- Quote ---ERROR 1 Overflow of measurement result
             Overshoot of the allowed  numerical span.

ERROR 4 Error during offset measurement
              The offset which is present at the input sockets is too large.
--- End quote ---
page 5/12

-branadic-

Rax:

--- Quote from: branadic on December 31, 2023, 09:05:09 am ---Is this with something connected at the input?
-branadic-

--- End quote ---

It comes up regardless. I start the meter with nothing at the input, so it'd run its startup checks undisturbed, and the error comes up right after the checks. The unit settles into the largest range on VDC. If I connect a short or a known voltage at the input, it stays on "Error 1," and if I try to null it with the short on the input it gives "Error 4." So no useful measurement would be rendered with both U9 and U10 replaced.

I may try to only replace one at a time and see where that takes me.

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