I agree generally with what others have said but with a big warning 
addendum. In a former life, my company made aqueous batch cleaners and 
we experimented with this technique in the 1970s. Apart from problems 
with hot water and DI resins, which were not insurmountable, we found 
that visibly badly cleaned rosin flux residues could give low 
conductivity readings (or high resistivity) simply because these 
residues were non-ionic. This led us to abandon closed-circuit DI 
washing/rinsing and then to the concept of high volume, medium pressure 
washing to jet nozzles for cleaning and low volume high pressure 
multiple DI rinses with fine spray nozzles in open circuit for the final 
rinse, followed by rotary high pressure air knives for drying, in closed 
and open circuits. These machines were much more effective (and 
expensive!) than the modified "dishwasher" concept that I started in 
1975 and the last machines I made (a hundred or so in the 1980s/early 
90s) were actually fifth generation. Info on this technology is thin on 
the Internet, but if you Google "APL-5 cleaning machine protonique", 
there are a few references. More details are found in my book.

Best regards,

Brian

On 01/02/2013 23:46, Watson, Howard A wrote:
> Hi all,
>
> My shop just bought a batch cleaner (dishwasher type); the manual says it is Aqueous Technologies, with an onboard cleanliness tester. This is a resistivity meter that measures the resistance of the rinse water, and I believe it has a range of 2k to 2000k ohm. This unit has both a closed-loop wash and  rinse, and we are using DI water. Does anyone have any experience with this type of cleaner with an "onboard cleanliness tester"?  Is this mostly for process control?  The manual is recommending a baseline cleanliness of 200-400 kOhm. I realize that this tester is not going to provide a level of cleanliness or contamination of each board processed, but I'm not sure what it is good for other than indicating the rinse water needs to be changed.
>
> I was not involved in the selection of this system, but tasked with qualifying it.  My previous experience has been with no-clean processes, so cleaners are new to me!  I should add that currently we process a very small volume of PCBAs for space. All work is hand assembly and cleaning is by hand with Ensolv. The goal is to get away from Ensolv while still achieving clean boards. This shop has never done ionic contamination testing, ROSE, SIR, etc.  I believe some people were sold on the "onboard cleanliness tester" as a cure-all for aqueous cleaning validation, but I'm skeptical as to the benefits.  Any insight is appreciated.
>
>
> Howard A. Watson
>
>
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