Electronics > Metrology

Prema 6048 teardown

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Hi everyone,

it just so happened that I bought a Prema 6048, which arrived today, so I now have a small collection of 8.5 digit meters (R6581D, S7081).
Since noone ever posted teardown pictures, this thread is addressing exactly that and also shows the hardware differences to Prema 6047, that Dave already torn down:


The meter arrived with a lot of Fluke stickers all over the place. Looks like it was calibrated in 08/2009?
Before powering the meter I visually inspected the meter and caps and took a few pictures, so this is just a first teaser, not a complete teardown yet.

The first difference is already known, Prema 6048 has a LTZ1000ACH reference, compared to LMx99 in Prema 6047. The reference board pretty much looks like how you're doin' and is a piggyback solution. Most likely from preaging and selection. Interestingly, they have choosen LT1078 instead of LT1013, while the circuit in the manual indicates LT1013 too. Maybe someone else can open his unit? Otherwise no fancy resistor magic going on here.
The reference is connected to where the LMx99 is populated on analog board in 6047. It pretty much looks like an afterthought. Some hermetically sealed RHK02 (now part of Vishay) 5k, 7k and 70k resistors can be found on the analog board.
But the most interesting part is, what is unpopulated in 6047. While we can find a PR BK7 on the analog board in both models, there is a second PR BK7 on the digital board. I was told that MickleT. revealed that this additional ADC is for temperature correction on the meter.

Edit: here is a link to MickleT.s findings: https://www.eevblog.com/forum/blog/eevblog-613-prema-6047-multimeter-teardown/msg441667/#msg441667

That's it for now, more pictures and measurement results on this meter coming soon.


Dr. Frank:
The MM2020 took place a few days too early, obviously.
Would've liked to play with that famous instrument, and of course to check its calibration. (I'm still missing my 2ppm :palm:)
Please shoot some pictures of the instrument, while measuring something. Beautiful.

Interesting that yours looks like it's been hacked in ... mine is actually a standard part of the board...

More complete board photo...

Thanks for sharing. Looks like your analog board is a later version (6048-1-5), compared to the one that is in my unit (6048-1-2 and SN 1027).
Meter is still warming up with inputs shorted and offset is already down to -2.4µV starting at about 200µV on first power on. Maybe the unit was switched off for quite some time and need to stabilize first.


Do you know what those round traces are? Is there any component on the other side of the board, held by the screw?


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