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RE: pH Meters and Electrodes
There's been a lot of discussion on pH probes and their
calibration here, but I wanted to point out some advances
I saw a year ago that looked interesting.
Apparently you can take an optical fiber and run it into your
tank, and send a light down the center of the fiber. A certain
amount of light will be "refracted" back into the fiber based
on the pH of the solution.
When I found this a year ago, I thought it was really cool.
They also had mounts for other sensors (temp, etc.) and
all were driven with light in a fiber optic line.
The efficiency of operation, no-wearing parts, no need for
calibration, and applicability in hazardous or volatile
environments are obvious (sometimes you just don't want
an electrical current inside the gas storage tank.)
I did a quick web search and couldn't find the source from
last year, but I did run across a similar type device at
http://www.topsensors.nl/ooe/phsensor.html
It's a little expensive and has a halogen lamp that may
wear out, though (the one I was looking for is just a
terminated fiber optic wire.)
FYI, I've seen a lot of other fiber optic measurement
devices that may be interesting to our hobby, such as
a fiber optic oxygen monitoring device at
http://www.instechlabs.com/oxygen.html
that measures oxygen by coating the end of the
fiber with a fluorophor captured in a sol-gel, and
then measuring the fluorescent quenching resulting
from oxygen binding to the material (a pulsed blue LED
is used, and we all know LEDs don't wear out.)
I'm thinking my automated system will be all fiber.
--charley
charleyb at cytomation_com