Searching \ for '[EE]: Liquid Acidity Sensor' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/io/sensors.htm?key=sensor
Search entire site for: 'Liquid Acidity Sensor'.

Exact match. Not showing close matches.
PICList Thread
'[EE]: Liquid Acidity Sensor'
2001\02\06@152807 by Alejandro Fubini

flavicon
picon face
Hello,

I was wondering if anyone knows of the existence of acidity sensors. I'm
thinking of building a tester for liquid acidity using a PIC 16F84 and some
sort of sensor, only I've never come accross one. Any suggestions will be
much appreciated.

Thanks
--Alex

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2001\02\06@153428 by M. Adam Davis

flavicon
face
Do a search for PH sensors.  Acidity is measured on the PH scale, so the
sensors are called PH sensors.

-Adam

Alejandro Fubini wrote:
{Quote hidden}

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2001\02\06@175147 by jamesnewton

face picon face
www.piclist.com/techref/io/sensor/ph.htm

---
James Newton (PICList Admin #3)
spam_OUTjamesnewtonTakeThisOuTspampiclist.com 1-619-652-0593
PIC/PICList FAQ: http://www.piclist.com or .org

{Original Message removed}

2001\02\06@175558 by Gennette, Bruce

flavicon
face
pH probes are most often used for this.
Basically they use a special type of glass that allows the ionic activity
(charge carriers) value in a liquid solution (usually water) to pass through
the wall to an electrode in a standard solution. The leakage between the
solutions inside and outside the special glass is measured and displayed as
an adjusted value between 10^0 and 10^14 (actually 10^0 to 10^7 each side of
10^7). Warning - the probes are expensive and easily poisoned (the glass has
its special properties permanently changed by reaction with a strong
chemical).

If you are only interested in testing the one type of solution - eg chlorine
in a swimming pool then you can measure some alternative property that is
indicitive of the pH, such as conductivity.

You'll find several PIC based conductivity probe projects on the net if you
search.  These also suffer from probe poisoning, but the probes are cheap
and easy to replace.

Bye.

> {Original Message removed}

2001\02\06@191754 by Alejandro Fubini

flavicon
picon face
I'm trying to test the acidity level in home brewed vinegar and thought
maybe this would be a good way to get to grips with programming PIC's. I
guess most sensors are not made to be stuck inside food... Oh well, I'll
have to think up of something else to build.

Thank you for your replies,
--Alex

{Original Message removed}

2001\02\07@005237 by Fritz Braun

flavicon
face
Alejandro:

There are pH probes available for food processing. Also, since your vinegar
is liquid, a common pH probe ( relatively inexpensive) should do.

Look at http://www.omega.com


Fritz


----- Original Message -----
From: "Alejandro Fubini" <.....alexKILLspamspam@spam@FUBINI.FREESERVE.CO.UK>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Tuesday, February 06, 2001 7:17 PM
Subject: Re: [EE]: Liquid Acidity Sensor


> I'm trying to test the acidity level in home brewed vinegar and thought
> maybe this would be a good way to get to grips with programming PIC's. I
> guess most sensors are not made to be stuck inside food... Oh well, I'll
> have to think up of something else to build.
>
> Thank you for your replies,
> --Alex
>
> {Original Message removed}

2001\02\07@035622 by Peter May

flavicon
face
I work for the CSIRO here in Canberra Australia (I am currently of on sick
leave)and we used to make our own PH Meters. I can supply an email address
if you wish of the electronics engineer who developed them..

Regards, Peter.

{Original Message removed}

2001\02\07@042544 by Vasile Surducan

flavicon
face
If you plan an industrial measurement only metallic electrodes or FET ion
sensitive electrodes may be taken in disscution, else you may play with
any glass electrodes. However you can't interface such electrodes directly
to 16F84. Maybe to 15f85 or 16F86 when will come to the market ( if they
come) or to any pic with AD. But high impedance amplifier ( except for
very expensive ion sensitive FET probe ) is required.
Vasile

On Wed, 7 Feb 2001, Peter May wrote:

> I work for the CSIRO here in Canberra Australia (I am currently of on sick
> leave)and we used to make our own PH Meters. I can supply an email address
> if you wish of the electronics engineer who developed them..
>
> Regards, Peter.
>
> {Original Message removed}

2001\02\07@113910 by Bill Westfield

face picon face
For a particular chemical (ie vinegar), you may be able to get away with
something far short of "real" pH electrodes - perhaps something as
conductivity between stainless electrodes.  I have a pool meter that is
claimed to measure chlorine/pH to tell when acid/chlorine should be added.
I don't believe that it does much more than measure conductivity, but then
once I do find the correct balance of the pool, any drift in conductivity
will indicate that something has changed...

Besides that, you may not WANT pH - IIRC, the pH of "strong" acids tends
to be constant over a wide range of concentrations - 5% HCl has about the
same pH as 30% HCl (2?)...

BillW

--
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


2001\02\17@151509 by Snail Instruments

flavicon
face
>Besides that, you may not WANT pH - IIRC, the pH of "strong" acids tends
>to be constant over a wide range of concentrations - 5% HCl has about the
>same pH as 30% HCl (2?)...

Little bit late, but...

the pH dependance on acid concentration is one of the well defined
relations in chemistry. For strong acid (like HCl, HBr, HI...)

pH = -log (c)

for weak acids, like acetic (vinigar), benzoic and other organic acids

pH = [pK-log(c)]/2

where c is molar concetration (in mol/L), pK is constant of disociation,
this is characteristics of the strength of particular acid and can be found
in chemistry tables.

Otherwise I would agree that pH is not a very good indication of acid
concentration in vinigar, conductivity is a bit better but can suffer from
any salt content, which come from the vine.

Personaly I would suggest a very simple, but not automated method - a
titration. Measure certain volume of your vinigar, dilute with distilled
water, add a little of phenolphtalein (acidobasic indicator), start adding
sodium hydroxide solution while stirring constantly until the solution is
pink (dark red is too much hydroxide). This will indicate that all acetic
acid has reacted with hydroxide. The hydroxide solution could be
standardized for instance by titration of bought vinigar.

Josef


=======================================================================
Electronical devices for chemical laboratory, custom electronics design
-----------------------------------------------------------------------
Snail Instruments                      Josef Hanzal, M. S.
Vojanova 615                           phone/fax: +420-311-624433
266 01 Beroun                          e-mail: .....snailKILLspamspam.....iol.cz
Czech Republic                         URL: http://www.vitrum.cz/snail/
GPS: 49deg58'28" North, 14deg 4'35" East
=======================================================================

--
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


2001\02\20@173623 by Gennette, Bruce

flavicon
face
Maybe you could automate the titration by watching conductivity.
It will be high at first due to the acid, then fall towards neutralisation,
then rise again due excess alkali.
You just establish the slope of the rise and fall, then solve the equations
simultaneously to find where they crossed.

This would allow the titration to be done cheaply, using small measuring
cylinders to measure out a test quantity of vinegar and multiple additions
of alkali to the test cell rather than expensive pipettes, burettes, special
chemicals, etc.
And of course a PIC to prompt the user, read the cell, do the calcs and
display the acidity value.

Bye

       {Original Message removed}

2001\02\20@174247 by Alice Campbell

flavicon
face
Well, how about using CO2 gas to titrate with, and automate
the gas flow with a pic?

http://www.thekrib.com/Plants/CO2/co2-pvc.html

alice

{Quote hidden}

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestspamspam_OUTmitvma.mit.edu


2001\02\26@173253 by Snail Instruments

flavicon
face
Hi Bruce, Alice and all,

unfortunately titration of weak acid with a strong base is not well suited for conductivity determination of equivalence point. The conductivity rises both before and after the equivalence, only at different slopes. Using weak base gives better result - first rise, then constant.

I guess photometric indication should work, pH metry as well, even calorimetry (measuring amount of heat generated by neutralizaton)...

{Quote hidden}

In case you don't seek EPA certification for your laboratory procedures, then you can use graduated syringe or even drops counting. Just compare drop count of your samaple with 8% vinigar bought at Smiths' and that's it (of course the drops should be counted by PIC :-)

>Well, how about using CO2 gas to titrate with, and automate
>the gas flow with a pic?

I'm affraid that noone is going to convince acetic acid to react with carbon dioxide.

Josef


=======================================================================
Electronical devices for chemical laboratory, custom electronics design
-----------------------------------------------------------------------
Snail Instruments                      Josef Hanzal, M. S.
Vojanova 615                           phone/fax: +420-311-624433
266 01 Beroun                          e-mail: @spam@snailKILLspamspamiol.cz
Czech Republic                         URL: http://www.vitrum.cz/snail/
GPS: 49deg58'28" North, 14deg 4'35" East
=======================================================================

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2001\02\26@181953 by Alice Campbell

flavicon
face
ouch, Josef, a little brain fade there,

shoulda said ammonia, and use a methyl orange end point and
read it photometrically with a pic.

alice

{Quote hidden}

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2001\02\28@023829 by Vasile Surducan

flavicon
face
If you've got the required sensitivity for a photometrical measurement
OPT301 from Burr-Brown is a good choice for detector ( unless your option
will be a Hamamatsu 1024 photodiode array and against a colorimeter
tehnique you'll like a spectrophotometer one )
Vasile


On Mon, 26 Feb 2001, Alice Campbell wrote:

{Quote hidden}

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


More... (looser matching)
- Last day of these posts
- In 2001 , 2002 only
- Today
- New search...