A hydrogen-ion responsive electrode usually consisting of a bulb, or other suitable form, of special glass attached to a stem of high resistance glass complete with internal reference electrode and internal filling solution system. Other geometrical forms may be appropriate for special applications, e.g. capillary electrode for measurement of blood pH.
PAC, 1985, 57, 531. 'Definition of pH scales, standard reference values, measurement of pH and related terminology (Recommendations 1984)' on page 540 (https://doi.org/10.1351/pac198557030531)