[albada]

Try looking for Beckman Zeromatic model. Again the accuracy as someone mentioned is in the probe itself. Get your buffer solutions to calibrate and you're set.
When I was doing photo chemical analysis in the 80s under military spec requirements, we used Beckman pH meters as the standard. Lots of Beckman stuff on eBay cheap.
http://www.ebay.com/itm/Beckman-Zero...item3cba92e07b
And, in best practice you leave them running all the time with the probe in a proper buffer solution.

Thanks for the suggestion. I'm realizing that I can't go cheap on the probe, so I'm looking at a refillable model from Thermo Scientific. Interesting that the Beckmans are cheap on eBay. I'd guess those meters were well north of US$1000 when new.

Mark Overton