[SI-LIST] Re: Guard Rings ... DC - dielectric absorption effects
- From: keithK EPD <epd2001usa@xxxxxxxxxxx>
- To: <ci249534@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 22 Nov 2010 16:22:31 -0500
A few more questions to the group:
1) if I use a guard ring would it be better to route it, very close or far away
from the ground ref that is on that layer?
a second question -> should it be close (say 5mil) around the
electrode or farther?
2) should there be 1 guard ring on top and/or 1 guard ring on the bottom layer
3) I have a series resistor (1m) on the input of each electrode , is it better
to keep the resistor closer to the electrode
or farther away? ( the distance between the op amp and the electrode is only
0.060") / 5 mil or 25 mil trace, obviously
no vias.
Thanks in advance !
Keith Kowal
www.product-designs.com
> Date: Mon, 22 Nov 2010 12:26:50 -0800
> From: ci249534@xxxxxxxxx
> Subject: [SI-LIST] Re: Guard Rings ... DC - dielectric absorption effects
> To: epd2001usa@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
>
> Keith,
> I'd like to bring one more comment on top of all the rest of good ideas and
> advices for this question:
>
> Depending on your specific physical design and functionality, dielectric
> absorption may affect measurements and performance due to very long time
> constant charge displacements inside the insulating materials, which from the
> circuit functionality and troubleshooting perspective may look like leakage
> currents.
>
> Cosmin Iorga,
> NoiseCoupling.com
> http://www.noisecoupling.com
> tel: (805) 231-9786
>
>
>
>
>
>
> ________________________________
> From: keithK EPD <epd2001usa@xxxxxxxxxxx>
> To: si-list@xxxxxxxxxxxxx
> Sent: Thu, November 18, 2010 7:24:06 PM
> Subject: [SI-LIST] Re: Guard Rings ... DC
>
> I am dealing with DC ! so, some of my questions are not for the entire High
> speed audience, so I apologize
>
>
> I have a 4 gig ohm electrode/electrodes(s) ..... my electrode spacing is
> 0.230"
> and my socket has a 0.175" diameter / 4 layer
>
> I haven't seen much lit on the subject -
>
> PCB material / voids / components / etch width to the 1 resistor into the
> opAmp
> / given 0.060" / slots req'd
>
> what does conformal coating do for me....
>
> comments, pointers to white papers, etc are welcome.
>
>
> Keith Kowal
>
> www.product-designs.com
>
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