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'[PIC]: TDS or conductivity sensor'
2001\10\15@134336 by Peter Tran

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I'd like to build a TDS meter using a PIC. Could someone please tell me
where I can find out some inexpensive conductivity sensors for this project?
Thanks for your help.

Peter

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2001\10\16@151417 by Peter Tran

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Repost, please response if you know where I can buy some inexpensive
conductivity sensors used to monitor the quality of drinking water. Thanks.

Peter

{Original Message removed}

2001\10\16@154247 by alice campbell

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Hello Peter,

Before we can help you, we need a little more information.  Is this for a commercial product, a science project, or a hobbyst project?  Is it lab-grade or field-grade?  What exactly are you trying to monitor in groundwater?  Are you trying to detect a change in quality, or trying to precisely determine the conductivity of water?  Is it surface or ground water?  Is it in-place, or from stored samples?

Natural water generally contains about 12-50 separate dissolved constituents, all of which contribute something to the conductivity of water. Some of these substances, like carbonation, can fizz in and fizz out, while others are pretty inert.  Exposure of groundwater to air can change the conductivity of the water without really affecting the concentrations of other dissolved salts.

So you see, we need to have some idea what you are trying to do, and how you are going about it, before we can suggest conductivity probes

Alice




> Repost, please response if you know where I can buy some inexpensive
> conductivity sensors used to monitor the quality of drinking water. Thanks.
>
> Peter
>
> {Original Message removed}

2001\10\16@164220 by Peter Tran

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Hello Alice,

Thanks for replying. This is a home project to monitor the quality of my
house drinking water. I am a little bit worrying about terrorists, who can
inject some toxic materials into the water line. Although the city is
monitoring it 24/7, but I want to monitor it myseft also.

I currently use a reverse osmosis system in my house to produce the drinking
water from the tap water. I plan to monitor the input and output water from
this system continously using two conductivity sensors and a PIC-based
microcontroller, which can alert me if the water quality is changed. In the
market, it is caled TDS meter, which is availale from $100 to several
thousand dollars. It's so expensive so I plan to build it myself. I think it
quite simple because the output of the conductivity sensor is usually
resistivity based, that I can use IC555 to generate and count the frequency.
So the only thing I need now is some good-quality-but-inexpensive
conductivity sensors. Please let me know if you know where I can buy them.
Thanks for your help.

Peter

{Original Message removed}

2001\10\16@170558 by =?iso-8859-1?B?Tm9tZWwgoA== ?=

Are you sure that toxins would cause varried conductivity? Salt and other electrolytes I believe would cause them to change but toxins?

Actually, test it...Get some rat poison and put it in some water and see if the continuity changes...

For a simple solution, without getting into this high tech stuff, just get a hamster and have your water supply feed directly into his drinking water...When the hamster dies, don't drink the water... ;)

{Original Message removed}

2001\10\16@171015 by cardcd

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PPMJI,
Peter, Alice was being both polite and factual.
Please let me be more blunt.
Conductivity alone is _not_ a valid measure of water quality!
If you will make yourself happier with such measurements, feel free.
=============
Chuck Card in sunny Arizona
Unlimited Sunsets

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2001\10\16@171505 by Ned Konz

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On Tuesday 16 October 2001 01:39 pm, Peter Tran wrote:

> Thanks for replying. This is a home project to monitor the quality of my
> house drinking water. I am a little bit worrying about terrorists, who can
> inject some toxic materials into the water line. Although the city is
> monitoring it 24/7, but I want to monitor it myseft also.

Practical attacks on water supplies would likely use biological or
other organic agents that probably wouldn't change the conductivity of the
water.

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2001\10\16@174621 by alice campbell

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Hello Peter,

I don't think this kind of meter will work in this application.  Just the temperature changes from night to day will change conductivity of your water as it comes into your house.

Two technologies come to mind for water protection, heat and  carbon filtration.

If you already have a filtration system, a carbon cannister would take care of most organic molecules.  But you have to change it regularly, and you will have to have a way to determine when it is used up.  And smelling funky is not a scientific way to do this.  Those of us in the big leagues send samples to a lab for analysis at $150 or more a pop to test our carbon.  THis is not practical for homes.

Boiling water before drinking, and making it into tea, is a simple means of removing many pathogens and volatile substances, plus you get tea.  Probably the easiest and most sensible approach.

alice

sorry it doesnt have a pic in it.



{Quote hidden}

> {Original Message removed}

2001\10\16@181031 by Peter Tran

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Thanks a lot, Alice

----- Original Message -----
From: "alice campbell" <.....electrifriedKILLspamspam@spam@GEOLOGIST.COM>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Tuesday, October 16, 2001 2:45 PM
Subject: Re: [PIC]: TDS or conductivity sensor


> Hello Peter,
>
> I don't think this kind of meter will work in this application.  Just the
temperature changes from night to day will change conductivity of your water
as it comes into your house.
>
> Two technologies come to mind for water protection, heat and  carbon
filtration.
>
> If you already have a filtration system, a carbon cannister would take
care of most organic molecules.  But you have to change it regularly, and
you will have to have a way to determine when it is used up.  And smelling
funky is not a scientific way to do this.  Those of us in the big leagues
send samples to a lab for analysis at $150 or more a pop to test our carbon.
THis is not practical for homes.
>
> Boiling water before drinking, and making it into tea, is a simple means
of removing many pathogens and volatile substances, plus you get tea.
Probably the easiest and most sensible approach.
{Quote hidden}

can
> > inject some toxic materials into the water line. Although the city is
> > monitoring it 24/7, but I want to monitor it myseft also.
> >
> > I currently use a reverse osmosis system in my house to produce the
drinking
> > water from the tap water. I plan to monitor the input and output water
from
> > this system continously using two conductivity sensors and a PIC-based
> > microcontroller, which can alert me if the water quality is changed. In
the
> > market, it is caled TDS meter, which is availale from $100 to several
> > thousand dollars. It's so expensive so I plan to build it myself. I
think it
> > quite simple because the output of the conductivity sensor is usually
> > resistivity based, that I can use IC555 to generate and count the
frequency.
> > So the only thing I need now is some good-quality-but-inexpensive
> > conductivity sensors. Please let me know if you know where I can buy
them.
{Quote hidden}

for a
> > commercial product, a science project, or a hobbyst project?  Is it
> > lab-grade or field-grade?  What exactly are you trying to monitor in
> > groundwater?  Are you trying to detect a change in quality, or trying to
> > precisely determine the conductivity of water?  Is it surface or ground
> > water?  Is it in-place, or from stored samples?
> > >
> > >  Natural water generally contains about 12-50 separate dissolved
> > constituents, all of which contribute something to the conductivity of
> > water. Some of these substances, like carbonation, can fizz in and fizz
out,
> > while others are pretty inert.  Exposure of groundwater to air can
change
> > the conductivity of the water without really affecting the
concentrations of
> > other dissolved salts.
> > >
> > > So you see, we need to have some idea what you are trying to do, and
how
{Quote hidden}

tell
> > me
> > > > > where I can find out some inexpensive conductivity sensors for
this
> > > > project?
> > > > > Thanks for your help.
> > > > >
> > > > >  Peter
> > > > >
> > > > > --
> > > > > http://www.piclist.com hint: The list server can filter out
subtopics
> > > > > (like ads or off topics) for you. See
http://www.piclist.com/#topics
{Quote hidden}

here
{Quote hidden}

to get it now!
{Quote hidden}

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2001\10\16@183700 by Josh Koffman

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You could boil pics and make pic tea, but I don't know if pics are food
grade products. They might have lead in them. Then again, if you add
enough sugar, you'll never notice.

Josh Koffman

Peter Tran wrote:
>
> Thanks a lot, Alice
>
> {Original Message removed}

2001\10\17@065240 by Vasile Surducan

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Whooh ! My daughter's hamster does NEVER drink water !
What king of hamster do you have ?
Vasile


On Wed, 17 Oct 2001, =?iso-8859-1?B?Tm9tZWwgoA== ?= wrote:

> Are you sure that toxins would cause varried conductivity? Salt and other electrolytes I believe would cause them to change but toxins?
>
> Actually, test it...Get some rat poison and put it in some water and see if the continuity changes...
>
> For a simple solution, without getting into this high tech stuff, just get a hamster and have your water supply feed directly into his drinking water...When the hamster dies, don't drink the water... ;)
>
> {Original Message removed}

2001\10\17@185836 by Peter L. Peres

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> Two technologies come to mind for water protection, heat and  carbon
> filtration.

imho replace heat with a 500W hard UV on-demand source and a suitable
slow-flow exposure unit (this requires a clean-water accumulator after
it). Heat does not really kill critters afaik. In warm countries you have
all sorts of interesting algae growing inside hot water pipes (which do
not go beyond 75C - the upper limit for hot tap water outside a lab). The
UV kills them very dead and also destroys many virii afaik but do not take
my word for it, check. So UV + sub-micron (actually 5 um is common I
think) carbon filter changed monthly sounds pretty good. In fact someone
makes exactly such a unit but I do not remember the make.

The hard UV will destroy all organic compunds and organisms if the
exposure is sufficient. Also many molecules will be split, among
them plastic, so the unit must be made of something else.

Peter

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2001\10\18@072748 by 742-9014

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> The hard UV will destroy all organic compunds and organisms if the
> exposure is sufficient. Also many molecules will be split, among
> them plastic, so the unit must be made of something else.

Hmm.  Makes you wonder what some of the harmless large organic molecules get
split into.


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Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, RemoveMEolinTakeThisOuTspamembedinc.com, http://www.embedinc.com

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2001\10\19@161346 by Peter L. Peres

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> Hmm.  Makes you wonder what some of the harmless large organic molecules
> get split into.

In theory the split bits of whatever you were thinking of recombine
immediately with locally available ions of suitable charge. For biological
purposes they should be k.o. this way. That's water most of the time (H+
and OH-). Hard UV photons carry enough energy to split C=C bonds afaik, so
all organic molecules will be eventually destroyed completely (broken down
to alkanes and alkyl compounds probably). I don't know if they carry
enough energy to break C-C too so they'd turn everything into methane and
methyl compounds eventually. But I am not a chemist... Anyway this takes
time (hours, days, years etc).

The ready made water steriliser equipment runs the lamp for several hours
a day if I am not wrong. Adding some reactive additives to the water
before irradiation improves cleaning. One possible additive is ozone
(perhaps bubble the water with air - the UV turns some of the oxygen in
the bubbles into ozone).

Peter

PS: I seem to remember that hard UV also splits water (into H2 and O2) but
I may be wrong. Maybe one of the analytical chemistry gurus could step in
here - and perhaps drop a hint as to where one finds a bond energy table
on the web - I have a program called cactus (demo I think) that does
something like this but as I said I am not a chemist. cactus is from Uni
Erlangen in Germany, I got it in a Suse linux disk.

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