The Main Sensor Types and What Each One Measures
Selecting sensors requires matching physical transduction principles to measurands while accounting for thermal drift, noise floor, and fab availability.
Electrochemical Gas Cells
Functional Definition
Amperometric transducers quantify the partial pressure of target gases through redox reactions occurring at an electrode interface. These electrochemical gas cells generate a current proportional to the concentration of the gas being measured. Operation relies on the diffusion of molecules through a porous membrane to reach a working electrode.
Operating Principle
Internal electrolyte provides the medium for ions to travel between electrodes. Most electrochemical gas cells utilize a four-electrode configuration consisting of working, reference, counter and auxiliary components to maintain a stable potential. This arrangement ensures that the reaction remains within a linear range even when gas concentrations spike.
The sensitivity of the device is typically expressed in microamps per part per million.
Calibration Requirement
Periodic verification against a certified gas standard accounts for the gradual depletion of the electrolyte and electrode poisoning. While electrochemical gas cells offer high selectivity for specific species such as carbon monoxide or hydrogen sulfide, cross-sensitivity to other gases can induce measurement errors. Temperature compensation is required because reaction kinetics vary with ambient conditions.
Most sensors require a minimum oxygen level to function over long periods.
Service Life
The physical degradation of the chemical components defines the end of the functional period for the assembly.