[volt-nuts] Making a Reference IC
Dr. David Kirkby (Kirkby Microwave Ltd)
drkirkby at kirkbymicrowave.co.uk
Mon Sep 14 07:08:52 EDT 2015
On 13 Sep 2015 09:15, "M K" <m1k3k1 at hotmail.com> wrote:
> There has been some of those references available second hand from ebay,
mostly pulled, but some may be counterfeit, so look for sellers with
pictures showing it as old..
Several sellers have more than 1, but with one photo, so you would have a
hard time arguing that your board is a fake just because it looks newer
than the photo. I believe it is standard practice to photograph a genuine
article but to ship a fake.
In any case, it is probably possible to make a board look older.
A used 3458A fetches several thousand USD, so I find it hard to believe
that many would be broken for parts. But even if there is a reason 3458As
are being broken up, why are other parts not showing up as often as the
I just looked on ebay for "3458A board" There are 10, of which 6 are the
voltage reference and the other 4 being various other 3458A boards.
Looking for "3458A PCB" changes it to 6 references and 2 two other PCBs. It
seems a bit suspicious to me that the one board that has wider usage than
the others is available in roughly 2~3 times the quantity of all other
boards put together.
We why don't we see 3458A front panels, power supplies etc, showing up
much - why all the voltage references?
The fact that there seems to be a market for 3458A reference boards
suggests to me that there would be a market for a voltage reference board
based on the same chip, but designed as a stand alone board.
I can think of a few improvements over a 3458A board.
1) Option to run from batteries to keep it as stable as possible when there
are power failures.
It should also make it possible to ship a board to another volt-nut,
keeping it powered in transit.
I don't know the power consumption of the reference, and I am aware that
there are some issues shipping batteries, but these seem much more relaxed
if the battery is inside equipment.
2) Option to run chip at a lower temperature than in a 3458A, as some have
claimed is better.
3) Temperature sensor that recorded min and max temperatures during
4) Ability to read time board has been powered on.
I for one would buy such a board, if someone produced one, either as a
blank PCB or populated with components & adjusted. Specialist components
would be more readily available is there was a number wanted.
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