Hanna Instruments portable meter for pH in mash, one model.
HI99151
This Hanna Instruments portable meter measures pH in mash, wort and beer, with an electrode built for them.
Mash pH decides enzyme activity, and therefore fermentability and the finished beer. A general-purpose electrode clogs on grain and protein within a few brews; this one has a junction that survives it.
An electrochemical meter is three things that fail separately: the electrode, which ages and eventually dies; the meter, which rarely goes wrong; and the calibration, which is only as recent as the last time somebody did it. Almost every bad reading traces to the first or the third.
Budget for electrodes as consumables, store them wet in storage solution rather than water, and calibrate against fresh buffers at the temperature you will measure at.
Measure mash pH on a cooled sample at a consistent temperature; the same mash reads meaningfully different hot and cool.
Supplied as one model.