[SI-LIST] Re: PCBoard construction for analog signals
- From: steve weir <weirsi@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 04 Feb 2014 03:32:01 -0800
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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>
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--
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