Re: Damned Projects!

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Sujet : Re: Damned Projects!
De : liz (at) *nospam* poppyrecords.invalid.invalid (Liz Tuddenham)
Groupes : sci.electronics.design
Date : 29. Dec 2024, 20:16:00
Autres entêtes
Organisation : Poppy Records
Message-ID : <1r5ccjk.jk46kq1ow3clcN%liz@poppyrecords.invalid.invalid>
References : 1 2 3 4 5
User-Agent : MacSOUP/2.4.6
Don <g@crcomp.net> wrote:

Liz Tuddenham wrote:
Don wrote:
>
Electrolysis can cause the DC sensor to degrade over time. An analog
adaptation from resistance to capacitance can curb this effect. The
above sensor needs to be altered to detect a dielectric difference
instead of an ohmic resistance.
>
Perhaps spme sort of adaptation of my conductivity meter circuit would
do the job:
<http://www.poppyrecords.co.uk/other/ConductivityMeter14.gif>
>
It generates floating AC with prevents electrolysis at the sensor and
uses synchronous rectification to eliminate spurious responses.  For
simplicity, the range switch could be replaced by a pot and the meter
drivers arranged to switch a relay.
 
Do the five Schmidt triggers in parallel after the oscillator act as a
buffer?

In this pareticular application, the source impedance of the signal is
effectively in series with the resistance of the conductivity cell, so
it needs to be as low as possible or it will affect the linearity of the
highest conductivity range.  This resistance is made 0.5 ohms by the
bottom resistor of the voltage divider which drives the cell.  (Two
1-ohm resistors in parallel)

That means that the top resistor of the divider needs to be in the
region of 750 ohms to get a reasonable signal.  Such a low impedance
across the output of a CD40106 could cause current limiting which would
give unpredicatable output levels, so several sections in parallel
ensure that there is no overloading.  All the sections must be driven
identically and be in the same chip, so that there is no significant
time difference to give rise to a moment when one output switches before
another and a huge current spike is drawn from the supply.

Besides, what ekse could you do with all those unused gates?


--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

Date Sujet#  Auteur
26 Dec 24 * Damned Projects!38Cursitor Doom
27 Dec 24 +- Re: Damned Projects!1Phil Hobbs
27 Dec 24 +* Re: Damned Projects!16john larkin
27 Dec 24 i+- Re: Damned Projects!1Cursitor Doom
27 Dec 24 i`* Re: Damned Projects!14Cursitor Doom
27 Dec 24 i `* Re: Damned Projects!13Arie de Muijnck
27 Dec 24 i  `* Re: Damned Projects!12Cursitor Doom
27 Dec 24 i   `* Re: Damned Projects!11Cursitor Doom
27 Dec 24 i    +- Re: Damned Projects!1ehsjr
27 Dec 24 i    +* Re: Damned Projects!2Liz Tuddenham
28 Dec 24 i    i`- Re: Damned Projects!1Cursitor Doom
28 Dec 24 i    `* Re: Damned Projects!7mas
28 Dec 24 i     +* Re: Damned Projects!2Liz Tuddenham
29 Dec 24 i     i`- Re: Damned Projects!1Cursitor Doom
29 Dec 24 i     `* Re: Damned Projects!4Martin Brown
29 Dec 24 i      +- Re: Damned Projects!1mas
29 Dec 24 i      `* Re: Damned Projects!2Cursitor Doom
29 Dec 24 i       `- Re: Damned Projects!1Joe Gwinn
27 Dec 24 +* Re: Damned Projects!11Bill Sloman
27 Dec 24 i`* Re: Damned Projects!10Don
27 Dec 24 i +* Re: Damned Projects!3Liz Tuddenham
29 Dec 24 i i`* Re: Damned Projects!2Don
29 Dec 24 i i `- Re: Damned Projects!1Liz Tuddenham
29 Dec 24 i `* Re: Damned Projects!6Carlos E.R.
31 Dec 24 i  +* Re: Damned Projects!3Don
31 Dec 24 i  i+- Re: Damned Projects!1Joe Gwinn
31 Dec 24 i  i`- Re: Damned Projects!1Liz Tuddenham
5 Jan 25 i  `* Re: Damned Projects!2Martin Brown
5 Jan 25 i   `- Re: Damned Projects!1Cursitor Doom
27 Dec 24 +- Re: Damned Projects!1bitrex
27 Dec 24 +- Re: Damned Projects!1Jeff Layman
28 Dec 24 +* Re: Damned Projects!6Wanderer
29 Dec 24 i+- Re: Damned Projects!1Bill Sloman
29 Dec 24 i+- Re: Damned Projects!1Cursitor Doom
29 Dec 24 i+- Re: Damned Projects!1Don
29 Dec 24 i+- Re: Damned Projects!1Don
29 Dec 24 i`- Re: Damned Projects!1Carlos E.R.
28 Dec 24 `- Re: Damned Projects!1Lasse Langwadt

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