Why does the glass bulb at the bottom of electrodes come in a variety of shapes?
The glass membrane on pH electrodes comes in a variety of different shapes based on the fitness for purpose of the electrode. The most common membrane shapes in use today are outlined below: In practice there is a trade-off between the speed of response of the electrode and its ruggedness, thus the application the electrode is being selected for will govern the choice of membrane design. The classical sphere shaped membrane offers low electrical resistance due to its large surface area but is relatively fragile. The cone shaped membrane is seen as a universal design as it is robust, of medium resistance and is easy to clean.
