Hi Steve: As others have correctly pointed out micro-Siemens and megohms are
simply the inverse of each other. 
Back to the washer. 
1. Have you tried running it without boards and cleaning chemistry(if
used)to see if it shows the same condition? That will help pinpoint whether
it's a cleaning Vs water problem.
2. Do you have an inline resistivity meter at the output side of your DI
system? If not you probably should. What does it read? If it has acceptable
readings then your DI treatment system is OK.
3. Are you doing any heating of the water after DI treatment prior to
introduction to the board washer? Improper materials of construction in the
heater can cause a loss in resistivity. This is also true for the rest of
the plumbing going to the washer.
4. It's possible the resistivity meter built into the washer control is bad.
It possibly may not be reading correctly or temperature compensating
correctly. There are fairly cheap handheld portable resistivity meters on
the market that you can cross check your washer with. We use an older one
made by Myron-L.

                                                        Good Luck
	
Michael Barmuta
	
Staff Engineer
	
Fluke Corp.
	
Everett WA
	
425-446-6076

-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Thursday, February 26, 2004 10:36 AM
To: [log in to unmask]
Subject: [TN] Conductivity and Resistivity Correlation


Hi All!

Is there any chart, formula, or conversion that I can use to correlate a 
conductivity reading to a resistivity reading?

The reason I'm asking is that I have a new batch cleaner that has been up
and 
running the last three weeks or so. One of the neat things with the cleaner 
is that during the rinse cycle, it monitors the rinse water resistivity to a

setting that you program in the machine. If it reaches that pre-programmed 
resistivity setpoint before completing the number of rinse cycles that you
program, 
it will terminate the rinse cycles and go into the dry cycle. If it never 
reaches the resistivity setpoint within the number of rinse cycles that
you've 
programmed, it will display "FAILED" on the touch screen. You can then run 
another cycle, or start trying to figure out why the boards didn't come
clean.

Well, everything has been going fine with the cleaner up until yesterday. 
Every batch of boards I ran failed the resistivity setting I had in the
machine. 

The manual recommends a setting between 350-750 kohms, I've had my setting
at 
550 kohms from the beginning, and everything has been fine. I've had to
lower 
the setting to 400 kohms so the batches would pass. It's still within the 
350-750 kohm range, but I'm curious why all of a sudden things won't pass at
550 
kohm like it's been doing the few weeks.

So I called tech support for the cleaner, and they feel that my input DI 
water may be going bad. I have a US Filters reverse osmosis filtering system
that 
dumps that water into Ion exchange columns and that water goes directly to
my 
cleaner. The DI system displays the conductivity of the output water in µS 
(micro-siemins). I want to correlate that to resistivity to see if my DI
water is 
truly going bad.

Thanks!

-Steve Gregory-

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