What is commonly referred to as Potential is in fact a potential difference: the difference between the potential at one point and the potential at another point, such as at the two ends of a battery (Figure 1).
In electrochemistry the standard hydrogen electrode has under standard conditions a potential of 0V by convention. This is used to give the potential for a single point, because it is referred to the 0V potential of the standard hydrogen electrode.
When two points with different potentials are connected to each other, the potential will equalize in a way similar as the law of the communicating vessels (Figure 2).
In case of electrical or electrochemical potentials electrons are exchanged between the two points. This electron current is used for example to make electronic devices operate (Figure 3).
Measuring the potential
A potential can be measured with a voltmeter, which in essence is also present in a potentiostat, galvanostat or EIS analyzer.
- A potentiostat is capable of applying a constant potential to a conducting surface. In contact with another object or liquid this surface acts as an electrode. The applied potential induces electrochemical reactions which cause electrons to flow with a certain number of electrons per second. As an example this phenomenon can be used to detect the presence of certain substances in a liquid. The EmStat and PalmSens series are potentiostats developed by PalmSens.
- A galvanostat is capable of applying a constant current through an electrolytic cell, this current can induce a change of the electrodes and/or the substance under research. An example for a galvanostat is the PalmSens4.
- An EIS analyzer is used to measure the resistance (as well as other parameters e.g. inductance) of a substance or article by applying a controlled sinusoidal potential wave and measuring the response to it. These measurements can be executed with the PalmSens4.