Re: [volt-nuts] Resistors for LTZ1000A circuit
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@febo.com:
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Today's Topics:
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@mediacombb.net
To: volt-nuts@febo.com
Subject: Re: [volt-nuts] Resistors for LTZ1000A circuit
Message-ID: 8ED467935EBC4B82B5DABC46445D8054@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:
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
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@t-online.de
To: volt-nuts@febo.com
Subject: Re: [volt-nuts] Resistors for LTZ1000A circuit
Message-ID: 52A778A2.7030802@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.
and follow the instructions there.
Message: 3
Date: Tue, 10 Dec 2013 23:49:19 +0100
From: Frank Stellmach frank.stellmach@freenet.de
To: volt-nuts@febo.com
Subject: [volt-nuts] Resistors for LTZ1000A circuit
Message-ID: 52A79A6F.7010207@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@xtra.co.nz
To: Discussion of precise voltage measurement volt-nuts@febo.com
Subject: Re: [volt-nuts] Resistors for LTZ1000A circuit
Message-ID: 52A7D115.1000001@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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End of volt-nuts Digest, Vol 52, Issue 2
Hello Jan,
some shameless self-plugging:
My Website has a ZIP with the eagle schematic and layout of one of the
Circuits discussed on this eevblog thread: I am the babysitter.
http://dg3hda.primeintrag.org/doku.php?id=ltz1000a
Hendrik
Am 11.12.2013 20:43, schrieb Jan Fredriksson:
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@febo.com:
(...)
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:
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
(...)