Making an electrode for a conductivity meter

In fact the commercial inductive sensors don't seem to be too good
below about 1mS/cm so they wouldn't be too good with tap water. which
isn't my idea of a low-conductivity liquid.
-----------
Bill Sloman, Nijmegen

 

[John Woodgate]

I read in sci.electronics.design that bill.sloman@ieee.org wrote (in
<1104366355.241964.316220@z14g2000cwz.googlegroups.com&gt about 'Making
an electrode for a conductivity meter', on Wed, 29 Dec 2004:

And don't forget that the windings on both inductor cores have got to be
non-progressive, otherwise you get an effective single turn around each
of the toroidal cores, which rather messes up the concept.

I don't understand 'progressive' in that context. Could you please
enlarge?
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Bill Sloman]

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> schreef in bericht
news:BZuFQ0A$K70BFwuy@jmwa.demon.co.uk...

I read in sci.electronics.design that bill.sloman@ieee.org wrote (in
1104366355.241964.316220@z14g2000cwz.googlegroups.com&gt about 'Making
an electrode for a conductivity meter', on Wed, 29 Dec 2004:

And don't forget that the windings on both inductor cores have got to be
non-progressive, otherwise you get an effective single turn around each
of the toroidal cores, which rather messes up the concept.

I don't understand 'progressive' in that context. Could you please
enlarge?

If you wind your wire around the toroid in the obvious way - starting at 0
degrees and adding turns until you get around to 360 degrees - you've made a
loop around the toroid.

Rayner and Kibble's "Coaxial AC Bridges" (ISBN 0-85274-389-0 and available
from NPL
http://www.npl.co.uk/electromagnetic/publications/guides/ac_bridges.html)
discusses this at length in section 4.2.1.

They list a couple of ways of making the winding non-progressive or
"astatic", starting with taking the end of the coil back around the toroid
to the start, which roughly cancels the loop, proceeding through the
Ayrton-Perry or "bootlace" technique where you put on half the turns going
clock-wise around the toroid, and the remainder back-tracking anti-clockwise
over the top of the first lot, to a more complicated variant where you wind
the first 25% of the turns over 180 degrees of the toroid, going around the
toroid clockwise, then wind the next 50% over the full 360 degrees, going
back around the toroid anti-clock wise, then reverse again to wind the last
25% over 180 degrees, going around the toroid clockwise back to your
starting point.

The last variant gives you a coil with less self-capacitance.

I posted most of this on s.e.d. on Mar 12 2003, at 1:32 am, in the thread
"Conductivity meter probe questions".

--------
Bill Sloman, Nijmegen

 

[John Woodgate]

I read in sci.electronics.design that Bill Sloman <bill.sloman@ieee.org>
wrote (in <cr0npf$8ta$1@reader10.wxs.nl&gt about 'Making an electrode for
a conductivity meter', on Thu, 30 Dec 2004:

I posted most of this on s.e.d. on Mar 12 2003, at 1:32 am, in the
thread "Conductivity meter probe questions".

Thank you for the information.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk