[volt-nuts] A new LTZ1000A transfer standard is born

Hendrik Dietrich don_hendi at gmx.de
Sat Mar 2 04:14:02 EST 2013

Good morning fellow nuts,

after a short planning and long wait times to get LTZ from china[1], PCB
from the Ruhr valley[2] and resistors from the UK[3], I was no longer
able to wait and slap everything together. 
It is a clone of the Williams design in Linear Technology AN86 with
2x25K in parallel as R4, as suggested by Dr. Frank Stellmach from this
maillist. The interesting resistors are General Resistance Econistors,
the zener plus is buffered with a further LT1013 before breakout with
4mm copper-tellur receptacles[4]. The LTZ1000A has a hat made from a
little plastic cap and a o-ring to fix it to the LTZ case. The positive
and negative out and also a hole for a guard are on a slotted part of
the PCB and around the LTZ I spent some holes to give it a bit of

It worked instantly, I didn't even try step-by-step startup, current
limiting was the only safety measure. No stability measurements yet, but
the HP34401A at work (where I soldered it during lunch break) and the
HP3456A at home have shown the same voltage (the 3456A is calibrated
against my work DMM).

After finishing the circuit board, I have put it into a tinned sheet
iron case[5] and made a makeshift thermoinsulation from bubble wrap and
a cardboard box. Result:


that is the newborn and one of the spare PCBs.

Planned next steps, any hints?

0. Keep it on the HP3456A today and watch infrequently and hope that
only the last digit might change
1. Put it in the thermal chamber at work (hot-cold-hot cycle, tmax=80°C)
2. keep it powered for a few weeks
3. Hook it to my 3456A and use EZGPIB to get some voltage-over-time
measurements for a few days, although I think that the drift+noise from
the HP reference and my LTZ are quite close
4. Beg a cal lab to do a un-accredited HP3458 measurement with results
written on a napkin to get a number! (Repeat after a year or so)



[1] ebay seller polida 2088
[2] http://www.fischer-leiterplatten.de
[3] http://www.rhopointgermany.com/
[4] http://www.multi-contact.de/

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