<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Two quick comments:</div><div class=""><br class=""><div class="">(1) I was always taught that in order to have deionized water, you *must* have a continuously circulating loop.</div><div class=""><br class=""></div><div class="">(2) Nothing in this business is “not difficult” ! If you do find something to be “not difficult”, then you have overlooked something. :-)</div><div class=""><br class=""></div><div class="">Good luck!</div><div class=""><br class=""></div><div class="">--Mike</div><div class=""><br class=""></div><div class="">On Feb 2, 2015, at 7:22 AM, Kamal Yadav <<a href="mailto:kamal.yadav@gmail.com" class="">kamal.yadav@gmail.com</a>> wrote:<div><blockquote type="cite" class=""><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Dear John, Noah, and Miller,<div class=""><br class=""></div><div class="">Thank you for your response. I have gone through the attachment sent by John and Noah, which is identical and discusses about the topic in detail. I did not know this one is going to be difficult as well...</div><div class=""><br class=""></div><div class="">We do not have a circulating DI water loop. We have a conductivity meter using which we try to periodically check the DI water resistivity in flowing condition in a beaker waiting for sufficient time. I was happy as it was showing 0.04 uS/cm :) as that would be around 25 Mohm-cm much more than 18.2 Mohm, until a faculty pointed out that it is theoretically impossible at that temperature and is evident from the attachments you sent.</div><div class=""><br class=""></div><div class="">We have another resistivity meter in Solar Cell Center, that one is new and gives good reading something on which we can believe, so far. Calibrating that meter after sometime need to be identified as informed by the supplier [Merc Millipore]. They do not know as of now!!</div><div class=""><br class=""></div><div class=""><b class="">Two Options I can see: [John, Noah, Miller, please comment].</b></div><div class=""><br class=""></div><div class="">1. These days 1 uS/cm standard is also available at NIST. But still far from ~ 0.055. The attachment claims ASTM standard even at 100 uS/cm can be used to calibrate UPW range resistivity meter? I am little confused whether I can use the standard, and whether it will be stable with its conductivity. We are ok as long as it shows more than 16 or 17 MOhm,..but certainly not 25 :). The good meter from Solar cell lab shows around 15 Mohm-cm so we know it may be accurate. Since it is flowing DI water in a beaker it would be little far from 18.2 compare to John's 17.5, I suppose!</div><div class=""><br class=""></div><div class="">2. Send out the meter to an outside agency, will work if agency is in India, otherwise I need to see how much it cost, which may be equal to buy a new one.</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Thanks,</div><div class="">Kamal.</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Sat, Jan 31, 2015 at 12:03 AM, Noah Clay <span dir="ltr" class=""><<a href="mailto:nclay@seas.upenn.edu" target="_blank" class="">nclay@seas.upenn.edu</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class="">Kamal,<div class=""><br class=""></div><div class="">Personally, I would send out your meter(s) for calibration by an expert. That said, here’s a reference from a company in the Boston area (google search: "calibrate ultrapure water conductivity meter”)</div><div class=""><br class=""></div><div class=""><a href="http://www.snowpure.com/docs/thornton-upw-resistivity-measurement.pdf" target="_blank" class="">http://www.snowpure.com/docs/thornton-upw-resistivity-measurement.pdf</a></div><div class=""><br class=""></div><div class="">Apparently, one can purchase standards from NIST for this (as stated in the above link), but I’m not sure if they have a standard in your range.</div><div class=""><br class=""></div><div class="">Here’s another link from the same search/query:</div><div class=""><br class=""></div><div class=""><a href="http://www.thermoscientific.com/content/dam/tfs/ATG/EPD/EPD%20Documents/Application%20&%20Technical%20Notes/Water%20Analysis%20Instruments%20and%20Supplies/Lab%20Electrodes%20and%20Sensors/Ion%20Selective%20Electrodes/AN-PUREWATER-E%20RevA-HIGHRES.pdf" target="_blank" class="">http://www.thermoscientific.com/content/dam/tfs/ATG/EPD/EPD%20Documents/Application%20&%20Technical%20Notes/Water%20Analysis%20Instruments%20and%20Supplies/Lab%20Electrodes%20and%20Sensors/Ion%20Selective%20Electrodes/AN-PUREWATER-E%20RevA-HIGHRES.pdf</a></div><div class=""><br class=""></div><div class="">Best of luck,</div><div class="">Noah Clay</div><div class=""><br class=""></div><div class=""><i class="">Director, Quattrone Nanofabrication Facility</i></div><div class=""><i class="">School of Engineering & Applied Sciences</i></div><div class=""><i class="">University of Pennsylvania</i></div><div class=""><i class=""><a href="http://nano.upenn.edu/" target="_blank" class="">nano.upenn.edu</a></i></div><div class=""><i class=""><br class=""></i></div><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class=""><div class="h5"><div class="">On Jan 30, 2015, at 11:12 AM, John Shott <<a href="mailto:shott@stanford.edu" target="_blank" class="">shott@stanford.edu</a>> wrote:</div><br class=""></div></div><div class=""><div class=""><div class="h5">
<div bgcolor="#FFFFFF" text="#000000" class="">
Kamal:<br class="">
<br class="">
Let me start by saying that I've never actually tried to calibrate
meters of this type. Why? Because it is not easy. Here is a good
reference article from over 15 years ago that describes the process
in great detail including the fact that the standard conductivity
solutions only go down to about 5 uS/cm ... which isn't very close
to the 0.06 uS/cm you are hoping to measure. They also talk about
separating the whole calibration process into the steps of
calibrating the meter itself (easy), the temperature probe
(reasonably easy), and the "cell constant" of the probe itself
(hard). A number of you will recognize that the author of this
paper works for a company that makes and sells resistivity probes
and monitors. This is not intended to be an endorsement of that, or
any other, company ... but, I think, indicates that detailed
calibration of DI resistivity monitoring systems is typically found
primarily in the companies that make and sell such instrumentation
rather than by the folks that use such instrumentation.<br class="">
<br class="">
Their solution for high-precision calibration was to measure UHP
water over a range of temperatures as a means of determining and/or
calibrating the cell constant. If you read this article, however,
you will conclude that this is not a procedure for the faint of
heart.<br class="">
<br class="">
In recirculating DI systems, I believe that it is more common to
have continuous resistivity monitoring on both the supply side and
return side of the system. In our case, we typically see supply and
return resistivity readings about 17.7 MOhm-cm or higher ... but
that rarely, if ever, read the theoretically expected 18.2 MOhm-cm.
In fact, it is not uncommon to see a return resistivity that is
slightly higher than the supply-side resistivity ... which would
seem unlikely.<br class="">
<br class="">
Then, on an occasional basis ... probably not as frequently as we
should ... we (well, a third-party analytical laboratory) collect
samples and have them measured for particle content, bacteria grown,
total oxidizable carbon, dissolved silica, and a 30-element
mass-spec analysis for metal levels in the ppt range that is
commonly used for DI systems. In short, there are lots of things
that CAN be wrong with DI water that are not seen by even an
accurate resistivity measurement. In other words, as long as our
resistivity readings are on the order of 17.5 MOhm-cm or above on
both supply and return lines, I, for one, don't worry about the
resistivity aspects of our water. In fact, earlier this week, I was
comparing these DI analytical test results with another frequent
contributor to this forum from the Bay Area institution with the
longest history as a university laboratory in this field.<br class="">
<br class="">
Finally, when you say "periodic monitoring" do you mean that you
have a probe in a continuously recirculating loop and you want to
look at the resistivity of that periodically ... or that you
occasionally collect a sample of water and are trying to measure
it's resistivity? If it is the latter, that can be tricky: when
exposed to air, DI water absorbs CO2 which forms carbonic acid that
can cause your resistivity numbers to degrade.<br class="">
<br class="">
My guess is some of the folks that run newer labs than ours will
have more details about the way that they monitor the DI water in
these newer operations.<br class="">
<br class="">
Let me know if you have any additional questions.<br class="">
<br class="">
John<br class="">
<br class="">
<div class="">On 1/30/2015 2:01 AM, Kamal Yadav
wrote:<br class="">
</div>
<blockquote type="cite" class="">
<div dir="ltr" class="">Dear All,
<div class=""><br class="">
</div>
<div class="">What is the best way to calibrate conductivity meters for
DI water resistivity periodic monitoring.</div>
<div class=""><br class="">
</div>
<div class="">Standard known conductivity solutions are available but
which one is good and stable for this range of measurement.
[18 MOhm-cm or ~ 0.06 uS/cm]</div>
<div class=""><br class="">
</div>
<div class="">Thanks a lot!<br clear="all" class="">
<div class=""><br class="">
</div>
-- <br class="">
<div class="">
<div dir="ltr" class="">
<div class="">Thanks,<br class="">
</div>
<div class="">Kamal Yadav</div>
<div class="">Sr. Process Technologist<br class="">
</div>
<div class="">IITBNF, EE Department, Annexe,</div>
<div class="">IIT Bombay, Powai</div>
<div class="">Mumbai 400076</div>
<div class="">Internal: 4435</div>
<div class="">Cell: 7506144798</div>
<div class="">Email: <a href="mailto:kamal.yadav@gmail.com" target="_blank" class="">kamal.yadav@gmail.com</a>,
<a href="mailto:kamalyadav@ee.iitb.ac.in" target="_blank" class="">kamalyadav@ee.iitb.ac.in</a></div>
</div>
</div>
</div>
</div>
<br class="">
<fieldset class=""></fieldset>
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</blockquote>
<br class="">
</div>
</div></div><span class=""><thornton-upw-resistivity-measurement.pdf></span>_______________________________________________<span class=""><br class="">labnetwork mailing list<br class=""><a href="mailto:labnetwork@mtl.mit.edu" target="_blank" class="">labnetwork@mtl.mit.edu</a><br class=""><a href="https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork" target="_blank" class="">https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork</a><br class=""></span></div></blockquote></div><br class=""></div></div></blockquote></div><br class=""><br clear="all" class=""><div class=""><br class=""></div>-- <br class=""><div class="gmail_signature"><div dir="ltr" class=""><div class="">Thanks,<br class=""></div><div class="">Kamal Yadav</div><div class="">Sr. Process Technologist<br class=""></div><div class="">IITBNF, EE Department, Annexe,</div><div class="">IIT Bombay, Powai</div><div class="">Mumbai 400076</div><div class="">Internal: 4435</div><div class="">Cell: 7506144798</div><div class="">Email: <a href="mailto:kamal.yadav@gmail.com" target="_blank" class="">kamal.yadav@gmail.com</a>, <a href="mailto:kamalyadav@ee.iitb.ac.in" target="_blank" class="">kamalyadav@ee.iitb.ac.in</a></div></div></div>
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