Can anyone help with designing a 0V reference? FB
0V reference
May 14, 2006
40 Replies
The intended accuracy and drift ? :-)
Rene
Thanks for the reply, Rene.
100% accuracy, 0% drift - It is critical that this is a 0.0000V reference. FBI was told that a resistor to ground would do it, with a capacitor to 0V to stabilise the voltage. What values of resistor and capacitor would you recommend for 1 amp? Fred
For your quoted 0.0000V reference at 1A the resistor needs to be
0V relative to what?
0.0000V is trivial. 0.0000000 is more difficult.
Best regards, Spehro Pefhany
"it\'s the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Hello Spehro,
Nah, replace the bolts with marine grade stainless and give it some more torque :-)
Regards, Joerg
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Nah, stainless is a bad conductor, worse then steel. Copper is what you need ;) If its a audio application, you will need a 101% super-duper-ultra-OFC-OMG-WTCF-STFU plated bolt made from 50 year old
5-times refined silver from a certain mine in england that was processed by a tibetian monk.Othwerise it will sound rough, cold, shady and dark. ;)
Are you one of them? ;)
Even marine-grade stainless steel is stainless by virtue of a thin and cohernet layer of chromium oxide - I don't know which one - which has an appreciable electrical resistance.
My conductivity meter stopped using stainless steel electrodes - a bad idea that I'd inherited - at the point where I could prove that the oxide film had an appreciable electrical resistance by changing that resistance by exposing the film to 2% aqueous sodium hydroxide (whose conductivity the meter had to monitor, along with that of the tap water that washed it away).
Bill Sloman, Nijmegen
would -273.16 degrees C help?
martin
Lots of unpleasant ways for 100nV to crop up..
Best regards, Spehro Pefhany
"it\'s the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
You left out "Dank" ;-)
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
Well, guys, this was meant as a joke...
Ok then, how 'bout a nice thick gold plating on everything? Of course only gold mined from a particular mine here in California in 1850.
Regards, Joerg
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A reference has never 1 amp. References just supply the voltage, not power. Lookup "supply" or "voltage regulator"
Rene
;-)
How pure? Gold-copper doesn't have much thermocouple voltage, but a couple tenths of a degree C would be enough to swamp 100nV. Galvanic action might be possible too.
Of course the advantage of selling such a 'reference' to unsophisticated customers would be that few would be able to test it sufficiently accurately to complain.
Best regards, Spehro Pefhany
"it\'s the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
In that case the reference has appreciable resistance / impedance.
An ideal reference would have zero impedance and laugh at an Amp.
Graham
You've been looking at some schematics that have 0Vref on them haven't you ? ( blushes )
Graham
An ideal reference yes, but actual references only supply a few mA at close to zero ohms
Rene
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