Hanna Instruments portable meter for pH in low-conductivity drinking water, one model.
HI99192
This Hanna Instruments portable meter measures pH in low-conductivity drinking water.
Clean water is hard to measure: with few ions to carry the signal, an ordinary electrode drifts and takes minutes to settle. An electrode designed for low ionic strength gives a stable reading where a general-purpose one wanders.
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.
Take the reading in a flowing or stirred sample; still low-conductivity water absorbs carbon dioxide from the air and the pH falls as you watch.
Supplied as one model.