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.
resistor values...
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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
Post by Frank StellmachI've described the theoretical background and measurements on my
LTZ1000 references (2 on my own, one identical of another volt-nut) parts
#1
http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/165/
Post by Frank StellmachThose 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
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
Post by Frank StellmachDoes 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.
Post by Frank StellmachThanks,
Randy Evans
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Post by Frank Stellmachand follow the instructions there.
------------------------------
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
Post by Frank StellmachFrank,
Is there a drawing or scan for the PCB for this circuit? Are the boards
or
Post by Frank Stellmachcompleted assemblies available for purchase?
The links to the taobao.com site in the blog are obviously dead; they
lead
Post by Frank Stellmachto 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
Post by Frank StellmachDave,
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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