[SI-LIST] Re: PCBoard construction for analog signals
- From: DAVID CUTHBERT <telegrapher9@xxxxxxxxx>
- To: epd2001usa@xxxxxxxxxxx
- Date: Tue, 4 Feb 2014 04:07:51 -0700
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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