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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