[SI-LIST] Re: PCBoard construction for analog signals
- From: steve weir <weirsi@xxxxxxxxxx>
- To: keithK EPD <epd2001usa@xxxxxxxxxxx>
- Date: Tue, 04 Feb 2014 21:23:58 -0800
Assume vector addition:
Pload = Vsource^2*Zload/(Zload+Zinterconnect+Zsource)^2
Steve.
On 2/4/2014 5:01 PM, keithK EPD wrote:
> Does Zo matter for low level signals?
> Does micro-strip behave better then other board constructions? (for
> low level applications, like mine)
>
> I appreciate your responses
> keith
>
>
> > Date: Tue, 4 Feb 2014 03:32:01 -0800
> > From: weirsi@xxxxxxxxxx
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: PCBoard construction for analog signals
> >
> > When it comes to low level analog my strong preference is to get to
> high
> > level analog and then to digital as close to the signal source as
> > possible. What as close as possible translates to of course ... depends.
> >
> > Steve.
> > On 2/4/2014 3:07 AM, DAVID CUTHBERT wrote:
> > > Keith,
> > > before any design a complete set of specifications is needed,
> otherwise the
> > > circuit may be under or over designed. For your 1 uA signal the
> basic specs
> > > are:
> > > - Accuracy
> > > - voltage on the 1 uA node
> > > - measurement bandwidth
> > > - maximum temperature
> > >
> > >
> > > >From these two specs you can derive:
> > >
> > > - maximum allowable leakage current of amplifiers and other components
> > > - maximum PCB leakage current
> > > - thermal and 1/f noise of components
> > >
> > > This information will drive the topology, the board material,
> guard traces
> > > (if any), driving guard traces, board material, stack-up, component
> > > selection, and so on.
> > >
> > > The *Keithley Low Level Measurements Handbook* is a must read for
> this type
> > > of design. http://www.keithley.com/promo/wb/1401
> > >
> > > Dave Cuthbert
> > >
> > > NARTE Certified EMC Engineer, consultant on EMC, every thing analog,
> > > power, instrumentation,
> > >
> > > Rubium Technology LLC
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > On Mon, Feb 3, 2014 at 5:46 PM, keithK EPD
> <epd2001usa@xxxxxxxxxxx> wrote:
> > >
> > >> I am using a mixed (rigid and flex) board (6 layers) for sense analog
> > >> signal around the order of 1uA (a current source). I have multible
> > >> sensors on this board .... after the sensors , the signal travels
> through
> > >> a 6" section of flex (now 3 layers) , and finally goes to a connector
> > >> away from the sensors.
> > >>
> > >> the questions are: what would be the best way to preserve the most
> > >> signal (x-talk) , interference, etc....
> > >> Should the signals be sandwiched between copper ...
> > >> all signals are analog in nature..... no digital levels anywhere.
> > >>
> > >> keith kowal
> > >> keith@xxxxxxxxxxxxxxxxxxx
> > >>
> > >> any rules of thumb and why would be helpful
> > >>
> > >>
> > >>
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> >
> > --
> > Steve Weir
> > IPBLOX, LLC
> > 1580 Grand Point Way
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> >
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--
Steve Weir
IPBLOX, LLC
1580 Grand Point Way
MS 34689
Reno, NV 89523-9998
www.ipblox.com
(775) 299-4236 Business
(866) 675-4630 Toll-free
(707) 780-1951 Fax
All contents Copyright (c)2013 IPBLOX, LLC. All Rights Reserved.
This e-mail may contain confidential material.
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and notify the sender.
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