Great info, Ode, thank you very much for reporting it. I have not done
the calibrating work to know the details, but just from reading the
info that comes with the meters one can see the resolution is much
lower- it seemed like half to me; as you point out it is more than
that. I love being able to read in tenths, it makes the readings
meaningful to the calculations (Faraday stuff). Mine reads a straight
one to one with the Faraday calcs, when I read the solution
immediately. It took a while to get enough readings to be able to make
that statement with confidence, but there it is.
Kathryn
On Oct 29, 2009, at 8:03 AM, Ode Coyote wrote:
A TDS meter takes +/- 2 uS of conductivity to read 1 PPM and does
it in whole digits.
That makes the resolution of an EC meter that only displays whole
digits, about twice that of a TDS meter.
Take out around +/-.9 % for not having decimal places and that's
around 90% as good a resolution.
Subtract that from 2 digit EC resolution and you get a TDS meter
that's +/- 40% as good as an EC meter that has a decimal place.
TDS meters sometimes have a nasty habit of skipping a digit while
calibrating them too... it just won't display a 5 or a 7 as you
twist the screw...jumping from 4 to 6, for example.
That's, at LEAST, a 4 uS **possible** built in read error and could
be as much as almost 8 uS with no way to tell which...depending on
where on the scale you are and that particular meter.
I've never seen an EC meter skip a digit.
Ode
At 06:29 PM 10/28/2009 -0600, you wrote:
Ode Coyote wrote:
A TDS, in effect reads in every OTHER digit of conductivity..not
even whole numbers.
That's something like 40% as good as a COM-100
Please clarify this for me. A TDS' smallest reading is 1.0? If that
is right what you are saying is that the actual microsiemens
reading of a TDS showing 1.0 is 2.0 microsiemens? Yes? No?
thanks,
sol
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