[volt-nuts] Resistors for LTZ1000A circuit

Wed Dec 11 14:43:07 EST 2013

Hi list,

None of the resistors actually need to be high presision. They need to have
the best possible stability, time, temperature wise. But actual resistance
values are not critical.

It would require a longer discussion to sort out all the why /how to select
resistor values...
Den 11 dec 2013 18:00 skrev <volt-nuts-request at febo.com>:

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> Today's Topics:
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>    1. Re: Resistors for LTZ1000A circuit (Dave M)
>    2. Re: Resistors for LTZ1000A circuit (Andreas Jahn)
>    3. Resistors for LTZ1000A circuit (Frank Stellmach)
>    4. Re: Resistors for LTZ1000A circuit (Bruce Griffiths)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 10 Dec 2013 13:46:36 -0600
> From: "Dave M" <dgminala at mediacombb.net>
> To: <volt-nuts at febo.com>
> Subject: Re: [volt-nuts] Resistors for LTZ1000A circuit
> Message-ID: <8ED467935EBC4B82B5DABC46445D8054 at D77M7BF1>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>         reply-type=original
>
> >
> > I've described the theoretical background and measurements on my
> > LTZ1000 references (2 on my own, one identical of another volt-nut) parts
> > #1
> > -#6, starting here:
> >
> >
> http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/165/
> >
> > Those 0.1% wirewound resistors, are available from stock, they are called
> > "econistors", 8G16, cost around 8$/? each and are distributed via a
> > british
> > company
> >
> >
> http://www.rhopointcomponents.com/components/resistors/precision-through-hole.html
> >
> > regards Frank
> >
>
> Frank,
> Is there a drawing or scan for the PCB for this circuit?  Are the boards or
> completed assemblies available for purchase?
> The links to the taobao.com site in the blog are obviously dead; they lead
> to a department store type retail site.
>
> Dave M
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Tue, 10 Dec 2013 21:25:06 +0100
> From: Andreas Jahn <Andreas_-_Jahn at t-online.de>
> To: volt-nuts at febo.com
> Subject: Re: [volt-nuts] Resistors for LTZ1000A circuit
> Message-ID: <52A778A2.7030802 at t-online.de>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hello Randy,
>
> another source could be the UPW50 or UPW25 series of wire wound resistors.
> Some values are available at RS-Components.
> the 70K = 50K + 20K
> the 12,5K = 10K + 2K + 500R (50 degrees setpoint temperature)
>
> another possibility is the trimming service of DigiKey for VSMP resistors.
>
> http://www.digikey.de/product-search/de/resistors/precision-trimmed-resistors/66806?k=vishay%20metal%20foil
> You can get every value within 4 ohms - 120K.
> the only disadvantage is that there is only little mechanical decoupling
> against PCB stress of SMD devices.
>
> With best regards
>
> Andreas
>
> Am 10.12.2013 04:01, schrieb Randy Evans:
> > Does anyone know a good, hopefully low cost, source for the precision
> resistors required for the LTZ1000A circuit as shown in the LTZ1000A data
> sheet.  I found the 1K and 120 ohm .01% resistors on Mouser but no source
> found for the 13K and 70K .01% resistors.  Vishay is quite expensive but i
> haven't contacted them directly.
> >
> > Thanks,
> >
> > Randy Evans
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>
> ------------------------------
>
> Message: 3
> Date: Tue, 10 Dec 2013 23:49:19 +0100
> From: Frank Stellmach <frank.stellmach at freenet.de>
> To: volt-nuts at febo.com
> Subject: [volt-nuts] Resistors for LTZ1000A circuit
> Message-ID: <52A79A6F.7010207 at freenet.de>
> Content-Type: text/plain; charset=ISO-8859-15; format=flowed
>
> Dave,
> well the schematic is the same as in the LT specification.
> My PCB is a prototype, and I would not like to publish it, because it
> contains several bugs.
> One one those bugs led to the first change of the initial LT
> specification, i.e. I discovered the parasitic diode in parallel to  the
> heater, by reversing the polarity.
>
> I did not put any taobao.. link anyywhere, so I don't know what you
> mean, sorry.
>
> Frank
>
> >Frank,
> >Is there a drawing or scan for the PCB for this circuit?  Are the boards
> or
> >completed assemblies available for purchase?
> >The links to the taobao.com site in the blog are obviously dead; they
> lead
> >to a department store type retail site.
> >
> >Dave M
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 11 Dec 2013 15:42:29 +1300
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> To: Discussion of precise voltage measurement <volt-nuts at febo.com>
> Subject: Re: [volt-nuts] Resistors for LTZ1000A circuit
> Message-ID: <52A7D115.1000001 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Frank Stellmach wrote:
> > Dave,
> > well the schematic is the same as in the LT specification.
> > My PCB is a prototype, and I would not like to publish it, because it
> > contains several bugs.
> > One one those bugs led to the first change of the initial LT
> > specification, i.e. I discovered the parasitic diode in parallel to
> > the heater, by reversing the polarity.
> >
> > I did not put any taobao.. link anyywhere, so I don't know what you
> > mean, sorry.
> >
> > Frank
> The datasheet heater circuit for the negative reference is still
> inconsistent with the block digram given on the datasheet in that the
> parasitic diode in parallel with the heater is formward biased.
>
> Bruce
>
>
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