What's the best piece of test equipment to measure mash pH?
if you are going to measure and then compensate for the pH during the mash you need a meter that reads quickly and is temperature compensated. I bought one like this on Ebay. http://www.ebay.com/itm/Digital-Waterproof-pH-Temp-C-F-0-14-Meter-Tester-Auto-Calibration-BIG-LCD-/200875806509?pt=LH_DefaultDomain_0&hash=item2ec521 8f2d You still need to cool the wort but I use a metal measuring cup into which I scoop just enough wort for the reading and set it in ice water to cool. I do BIAB and with that I get conversion in less than 20 minutes so I need the reading quickly if I am going to adjust. This meter reads quickly enough for that.
I won't buy anything from Hong Kong anymore.
I use this one: http://www.ebay.com/itm/Hanna-Checker1-pH-Meter-FREE-Calibration-Buffer-/170543846662?pt=LH_DefaultDomain_0&hash=item27b534 9506
It has a replaceable probe, and mine has lasted years.
BTW, you also need some buffer solution. Get a bottle of 4ph and a bottle of 7ph for calibrating. You'll also want some storage solution, which is the same chemical as what is in the probe. It will help make the probe last a long time.
Keg #1: Two-row/homegrown Cascade Smash
Keg #2: Cascadian Stout
Keg #3: BMC West
Keg #4 RHESB 6.1
Fermenter #1 Thor's Hammer