what are the parts and functions of a portable pH meter?

Answer 1

The only difference in a portable is that it has a battery pack instead of or in addition to a power cord.

The basic phenomenon upon which the pH meter operates is the development of an electrical potential (voltage) by a chemical reaction in an electrochemical cell. Such a cell consists of two dissimilar half cells, different in materials or concentration, separated by a semipermeable membrane. This allows for the contact of the two solutions but does not allow mixing and hence direct reaction of the substances in the two half cells. The voltage is measured across the two electrodes in the half cells.

The system consists of a pH sensor, pH Half Cell, whose voltage varies proportionately to the hydrogen ion activity of the solution, and a reference electrode, Reference Half Cell, which provides a stable and constant reference voltage.

The pH electrode consists of a thin membrane of Hydrogen sensitive glass blown on the end of an inert glass tube. Because this is a special type of glass and very thin, the bulb is very fragile and great care must be exercised in handling it.

This tube is filled with an electrolyte, and the signal is carried through Ag/AgCL wire. This is a pH half Cell.

A similar system, but without using a Hydrogen sensitive glass, is used as a reference. A small filter (diaphragm) connects this tube to the external liquid. This system is called a Reference Half Cell.

It is very common to find pH meters which are fitted with only a single combination electrode. As the name implies, a combination electrode is a combination of the glass electrode and the reference electrode into a single probe. The probe is constructed with the reference surrounding the glass electrode. The primary advantage to using a combination electrode is the ability to measure the pH of a smaller volume of sample or a sample in a container with a restricted opening. The main disadvantages to using a combination electrode are the more limited selection of internal elements (most have only a silver-silver chloride internal reference) and the higher cost.

Answer 2

Simply put: The [H(+)] concentration gradient creates a voltage difference across the glass electrode proportional to the log([H(+)]). CONDUCTIVITY???? Oh wow. So what is the pH of sat'd NaCl solution?