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'[ot]: Is distilled water an insulating fluid?'
2003\08\20@222152 by rad0

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Is distilled water an insulator?

Will the two probe, capacitance circuit work to
detect the level of distilled water?

Thanks

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2003\08\20@223427 by Jinx

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> Is distilled water an insulator?

Yes, if it's truly 100% H2O

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2003\08\20@234912 by rad0

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OK, what I meant to say was:

Is what you get from a boiled water distiller machine,
an insulating fluid?


Thanks

Or, will a two probe capacitance level sensor
work on this product mentioned above?







{Original Message removed}

2003\08\21@003737 by Brent Brown

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On 20 Aug 2003 at 22:48, rad0 wrote:

> OK, what I meant to say was:
>
> Is what you get from a boiled water distiller machine,
> an insulating fluid?
>
>
> Thanks
>
> Or, will a two probe capacitance level sensor
> work on this product mentioned above?

Depends what type of capacitive sensor you mean.

The kind that changes frequency due to the dielectric characteristic
of liquid between two fixed plates may still be OK for detecting
presence/abcence of pure water.

The other kind that relies on capacitive coupling into a conductive
liquid to load down an oscillator might be a different story.

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2003\08\21@003743 by Jinx

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> Is what you get from a boiled water distiller machine,
> an insulating fluid?
>
>
> Thanks
>
> Or, will a two probe capacitance level sensor
> work on this product mentioned above?

Possibly. Have a read of this page. Saves me a lot of typing ;-)

http://www.ganoksin.com/orchid/archive/9909/msg00420.htm

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2003\08\21@070510 by rad0

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thanks all,

I think I'll just try the two probe set up and see if it works,
I thought I could use the same circuit and switch between
three probes.  And it is pretty cheap too.

The info on distilled water is interesting, thanks.

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2003\08\21@071840 by Jinx

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> thanks all,
>
> I think I'll just try the two probe set up and see if it works,

Sorry you couldn't get a definitive answer. It's likely just one of
those things that most people would have any experience of.
And that does leave you with finding out for yourself

> The info on distilled water is interesting, thanks.

It's been some time since I had a professional interest in water.
We had 4 grades - kitchen, lab, analytical and the one which
gets you sopping wet on the way to and from work. (Some of
the quality control lab ruffians had another - a blend of water,
alcohol and fermented grain. Hmmm, what was their lab motto
again ?  Oh yeah - "sink more piss". A rather quaint working
class colloquialism for party party party ;-)))) )

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2003\08\21@084550 by Spehro Pefhany

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At 10:48 PM 8/20/2003 -0500, you wrote:
>OK, what I meant to say was:
>
>Is what you get from a boiled water distiller machine,
>an insulating fluid?

Not really. De-ionized water has a pretty high resistivity, but it's
easily contaminated by ions and the resistivity will drop as a result.

Water can be used as a dielectric in some circumstances (eg. EDM
machines). Being a polar molecule It has quite a high dielectric constant
(~80, IIRC) in the liquid state.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
.....speffKILLspamspam@spam@interlog.com             Info for manufacturers: http://www.trexon.com
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2003\08\21@085212 by M. Adam Davis

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Ah, so that's what is meant when I heard someone say that water is
"self-ionizing".

-Adam

Jinx wrote:

{Quote hidden}

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2003\08\21@111506 by Bob Axtell

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The problem with water is that while it might be pure ONCE, it won't stay
that way. Water dissolves- and is contaminated by- just about everything.

--Bob

At 04:13 PM 8/21/2003 +1200, you wrote:
{Quote hidden}

--------------
Bob Axtell
PIC Hardware & Firmware Dev
Tucson, AZ
1-512-219-2363

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2003\08\21@113648 by Harold Hallikainen
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Regarding level measurement using capacity, it seems that if the probes themselves are insulated, it would matter little if the water conducts. You could consider the probes to be two capacitors in series. One is formed by the first probe, its insulation, and the water as the second plate. The other is formed by the water as the first plate, the insulator of the second probe, then the conductor of the second probe. As the water level varies, the "plate area" of each probe would vary, varying the capacity.

The contamination of the water may also not affect measurement of dielectric constant with insulated probes. I made some calibration equipment for the oil industry that determines how much water is mixed with the oil in a pipeline. A section of pipe had an insulated probe in the middle of the pipe (a sort of symmetrical bullet shaped thing that was co-axial with the pipe) with a contact outside the pipe. The instrument measured the capacity between this probe and the grounded pipe. I don't recall how the capacity measurement was actually done (I did the calibrator, not the instrument).

Finally, speaking of capacity measurement, I find the capacity measurement circuit in many hand held digital meters to be clever. The ones that I've looked at have either a Wein Bridge or Twin-T sine wave oscillator driving one terminal of the capacitor. The other terminal drives a standard op-amp current to voltage converter. The voltage out of the current to voltage converter is proportional to the capacity. Real simple! This does, however, require the capacitor to be floating.

Harold



FCC Rules Online at http://www.hallikainen.com



--- Bob Axtell <.....cr_axtellKILLspamspam.....YAHOO.COM> wrote:

The problem with water is that while it might be pure ONCE, it won't stay
that way. Water dissolves- and is contaminated by- just about everything.

--Bob

At 04:13 PM 8/21/2003 +1200, you wrote:
{Quote hidden}

--------------
Bob Axtell
PIC Hardware & Firmware Dev
Tucson, AZ
1-512-219-2363

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2003\08\21@114516 by Spehro Pefhany

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At 03:36 PM 8/21/2003 +0000, you wrote:
>Regarding level measurement using capacity, it seems that if the probes
>themselves are insulated, it would matter little if the water conducts.
>You could consider the probes to be two capacitors in series. One is
>formed by the first probe, its insulation, and the water as the second
>plate. The other is formed by the water as the first plate, the insulator
>of the second probe, then the conductor of the second probe. As the water
>level varies, the "plate area" of each probe would vary, varying the capacity.

Assuming we're using sine wave excitation and measuring the impedance:

            Cx
     Cs       /      Cs
o----||--x--|/|---x--||------o
         |  /     |
         |        |
         +---Rp---x

For Cx to dominate, we would like 2* Cx << Cs

For Rp to be negligible, we would like Xc << Rp, so a relatively high
frequency is called for. (Xc = 1/wC  where w is the freq. in radians/sec)

{Quote hidden}

It takes a more complex bridge circuit to eliminate the effect of Rp
where it's significant. The LRC bridge instruments do this.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamspam_OUTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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2003\08\21@123108 by Sergio Masci

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From: Bob Axtell wrote:

> The problem with water is that while it might be pure ONCE, it won't stay
> that way. Water dissolves- and is contaminated by- just about everything.
>
> --Bob
>

Yes, even itself.

Water ionically dissociates into hydrogen and hydroxyl ions in other words H2O
goes to H+ and OH- (actually the hydrogen ions are hydrated to hydroxonium ions
to form [H(H2O)n]+ )

So pure water does contain charge carriers and is not an insulating fluid in the
same sense that an organic liquid such as carbon tetrachloride is an insulating
fluid.

The ionic product of water is 10^-14 (10 to the power -14) at 25 C but increases
rapidly with temperature. In other words the conductivity changes with
temperature.

Regards
Sergio Masci

http://www.xcprod.com/titan/XCSB - optimising structured PIC BASIC compiler

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2003\08\21@124724 by Richard J. Pytelewski

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True distilled water has no ability to transmit electrons so it is an
"insulator"

-----Original Message-----
From: pic microcontroller discussion list
[@spam@PICLISTKILLspamspamMITVMA.MIT.EDU]On Behalf Of rad0
Sent: Wednesday, August 20, 2003 7:20 PM
To: KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU
Subject: [ot]: Is distilled water an insulating fluid?


Is distilled water an insulator?

Will the two probe, capacitance circuit work to
detect the level of distilled water?

Thanks

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2003\08\21@140902 by Arutner

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In a message dated 8/21/03 12:49:00 PM Eastern Daylight Time,
RemoveMEres0bidcTakeThisOuTspamVERIZON.NET writes:

> Is distilled water an insulator?
>

This OT topic piqued my interest and so I dug up my copy of "Handbook of
Chemistry and Physics" 40th edition 1959 pp 3456; published by Chemical Rubber
Publishing Co. price December 1960 US$ 5.75 (!!)"

      Dialectic constant of water:  88.00 at 0 degree C     55.33 at 100
degree C

       Resistance in ohms per centimeter cubed:
                         Distilled water at 18 degree C   =  0.5 x 10^6
                          Petroleum at ? degree C         =  2 x 10 ^16

       clearly there is sufficient diference in resistivity to detect water
contamination in "petroleum".

       On the matter of purity and how long it stays pure:

        In 1961, as part of a research program investigating the roll of
trace metals in biochemical processes, I needed water with less than 10 part per
billion (10^9) contamination with zinc and other elements. This was acheived
with municipal water passed over cation and anion exchange resins, then double
distilled and checked by atomic absorption spectrophotometry. All containers
were pretreated with at least three cycles of washing with aqueous non ionic
detergent followed by 10% hydrochloric acid, water, 10% sodium hydroxide, then
water. We used pyrex or kimex glass, tygon tubing and polypropylene reagent
bottles. This process leached out ionic contamination and gave at least a 6-12
month shelf life of stock solutions. Clearly a labor and time intensive process.

       All purity is relative (I'm not reffering to morals).

Alan

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2003\08\21@165528 by Dave Tweed

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Alan <spamBeGoneArutnerspamBeGonespamAOL.COM> wrote:
> TakeThisOuTres0bidcEraseMEspamspam_OUTVERIZON.NET writes:
> > Is distilled water an insulator?
>
> This OT topic piqued my interest and so I dug up my copy of "Handbook of
> Chemistry and Physics" 40th edition 1959 pp 3456; published by Chemical
> Rubber Publishing Co. price December 1960 US$ 5.75 (!!)"
>
>        Dialectic constant of water:  88.00 at 0 degree C     55.33 at 100
> degree C
>
>         Resistance in ohms per centimeter cubed:
>                           Distilled water at 18 degree C   =  0.5 x 10^6
>                            Petroleum at ? degree C         =  2 x 10 ^16

Better get a new handbook! Volumetric resistivity has units of ohm-cm, not
ohm/cm^3. This paper gives some relevant data:

 http://www.purite.co.uk/technical/CHARACTERISTICS_OF_DEIONISED_WATER.pdf

"Ultra-pure" water falls in the range 10-18  Mohm-cm
"Pure" water falls in the range        1-5   Mohm-cm
"Purified" water falls in the range   20-500 kohm-cm

Apparently, the theoretical maximum resistivity at 25C is 18.3 Mohm-cm,
which means that a 1-cm cube of water would measure 18.3 Mohm across
opposite faces. Whether this qualifies as an insulator depends on the
application, I guess.

Resistivity goes higher at lower temperatures. I guess pure ice really
is an insulator.

-- Dave Tweed

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