Re: [volt-nuts] PCBs with ceramic substrates

[Andy Bardagjy]

Synthetic sapphire has come down in price quite a bit, a 25mm dia 5mm thick
sapphire window can be had for just $71

https://www.thorlabs.com/thorproduct.cfm?partnumber=WG31050

Andy ◉ Bardagjy.com  ◉ +1-404-964-1641

On Sun, Apr 16, 2017 at 12:03 PM, Scott Stobbe 
wrote:

> As a practical aside regarding surface resistance, ignoring guard
> amplifiers and guard traces, the historic solution is to point to point
> wire in air. With some designs using Teflon standoffs for a more rigid
> approach. Some of this can still be seen today, your smoke-detector likely
> has a one-layer phenonlic PCB with the sense pin of a DIP package IC bent
> up off board and point-point wired in air to the Ion chamber.
>
> On Sun, Apr 16, 2017 at 1:25 PM, f...@gmx.net  wrote:
>
> > Possibly Macor (machinable ceramic) from Corning, or the comparable
> > Vitronit, which are both glass ceramics.
> >
> > Comparable to borosilicate glass.
> > Extremely machinable (HSS or carbide tools, use proper speeds and
> > coolant), continously stable until 800°C.
> > No safety concerns or toxic effects. The dust created when machining can
> > be an irritant.
> >
> > Available from Corning as standard size maxi slab of 36*36*6 cm.
> > Price = ?
> >
> > Quoting Wikipedia for technical data for Macor:
> > ---
> > Density: 2.52 g/cm³
> > Young's modulus [GPa @ 25°C]: 66.9  (FR4 = 21 - 24, Aluminium = 69, Steel
> > = 200)
> > Specific stiffness [E6 m²/s²]: 26.55  (Al = 26, Steel = 25 +/- 0.5)
> > Poisson's Ratio []: 0.29 (FR4 = 0.118 - 0.136, Al = 0.32, Steel =
> > 0.27-0.31)
> > Thermal conductivity [W/(m*K)]: 1.46  (FR4 ~ 0.3 - 1, Al ~ 300, Steel ~
> > 15-50)
> > compressive strenght [MPa]: ~350
> > Electrical resistivity [Ohm*cm]: 1 E17 (FR4 = 1 E14, PTFE = 1 E23 to 1
> E25)
> > Coefficient of thermal expansion [E-6 m/(m*K)]: 9.3 (FR4 ~ 13 , Copper =
> > 16.6)
> >
> > Firat
> >
> >
> > Am 16.04.2017 um 13:08 schrieb John Devereux:
> >
> >>
> >> Hi Chuck
> >>
> >> But the context is "PCBs with ceramic substrates". Are any of *those*
> >> tough? They may well be, perhaps you know of some? It does not help us
> >> with the subject much if there are ceramics with these amazing
> >> properties if they are not available as PCBs.
> >>
> >> There is also the question of exactly what properties of FR4 are
> >> limiting for "metrology" use.
> >>
> >> John
> >>
> >
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Re: [volt-nuts] ***SPAM*** Re: Some questions to zeners (1N823-1N829)

[Andy Bardagjy]

The ADS1282 is a really cool part! After studying the ADS1282
datasheet is appears that *at best* it can achieve 130dB SNR which, by
my calculations is effectively 21.3 bits - by the formula
SNR=(6.02N+1.786)dB.

This got me thinking, are there any higher performing 24 bit ADCs we
should look at for our nuttery. One that I found is the Linear
LTC2440 (and others in the family). It claims, at its highest
resolution, 24.6 effective bits. That said, I am having trouble
comparing SNR directly. I need to read more to understand how to
convert its noise spec - 200nV RMS noise - to a SNR dB figure.

Andy Bardagjy
bardagjy.com


On Tue, Jan 29, 2013 at 4:43 AM, Тимофеев Михаил timk...@yandex.ru wrote:
 The ADS1282 offers outstanding specification, but not very useful in the 
 wide-scale DVM application range due to low input and reference voltages.
 Within a year I'm trying to develop a design of the selfcal 7.5-digits DMM 
 with ADS1282 ADC. Reference (+/- 10V) is a aged 1N829A with 0.03ppm noise and 
 2nd order TC correction, downscaled to +/-2.5 V with zero TC divider.

 Mickle T.


 29.01.2013, 11:38, Poul-Henning Kamp p...@phk.freebsd.dk:
 Content-Type: text/plain; charset=ISO-8859-1
 
 In message AA473A4936944A1199FC6F4C9C5D9A1A@laptop, Andreas Jahn writes:

 Amazing!

 Recently I came across a very interesting ADC from TI, designed for
 use with geophones: ADS1282

 It might be interesting for volt-nuttery:  It samples 2 bits at
 4MHz, which are then downsampled to 31 bits at 4kHz or less.  For
 this reason it is incredibly linear and has very good S/N.

 --
 Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
 p...@freebsd.org | TCP/IP since RFC 956
 FreeBSD committer   | BSD since 4.3-tahoe
 Never attribute to malice what can adequately be explained by incompetence.
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