Many toxic gases are also very reactive, and under appropriate conditions change with chemical reactions.
An electrochemical sensor is a micro-reactor, which with the presence of reactive gases, produces electrons exactly like a battery.
The flow of electrons is a very low, but still measurable electric current.
An electrochemical sensor consists of at least two electrodes (measuring electrode and counter electrode) that have an electrical contact in two different ways: in one hand via an electrically conductive medium called electrolyte (a pasty liquid to transport ions), and in the other, via a circuit of external electrical current (a simple copper cable to carry electrons).
The electrodes are made of a special material that also has catalytic characteristics making possible chemical reactions in the so-called 3-phase zone, where there is presence of gas, solid catalyst and liquid electrolyte.
The electron collector, needed for this reaction, oxygen, comes from the ambient air.
More electron collectors are known, like chlorine, fluorine, ozone or nitrogen dioxide.
In this way the current of the sensors used for these gases flows in an inverted direction, this current can be measured with a micro-ammeter.
More than a hundred gases and vapors are detectable by the Dräger electrochemical sensors. Some of these react very specifically to standard gas, others are typical gas group sensors that are sensitive to different reactive gases.
The Dräger electrochemical sensors are mainly equipped with three electrodes, a measuring electrode, a counter electrode and a reference electrode. The measurement capacity of the sensor is increased by a bias voltage (polarization) measured and maintained constant by the reference electrode and an electronic control circuit (the so-called potentiostatic circuit).
Additionally there is a temperature measuring element inside the sensor, because the electrochemical processes are extremely dependent on the temperature and therefore need to be compensated.
Only by the external electrical circuit of the sensor (especially for the temperature compensation and the amplification and the conditioning of the very low and noisy sensor current – only a few microamps) that produces a 4-20-mA signal, the electrochemical sensor is It converts into a real gas detector.
Electrochemical sensors just need a very low amount of energy, so they can work in intrinsically safe enviorements.
Thank you for reading.