Measuring, signalling and checking apparatus and instruments, namely, temperature sensors, pressure sensors, moisture sensors, fluid quantity sensors, fluid flow sensors, electric conductivity sensors and electrochemical sensors, electrical and electronic probes, meters, electrical and electronic indicators, transmitters, electrical transducers and electronic transducers; electric and electronic control and regulating apparatus, namely, control valves for regulating the flow of gasses and liquids, gas pressure regulators, liquid pressure regulators, thermostats, hygrostats, and process controllers for controlling temperature, pressure, moisture, fluid quantity, and fluid flow; protective apparatus and safety devices, in particular for influencing process engineering processes, namely, temperature switches, pressure switches, moisture switches, fluid quantity switches, fluid flow switches, electric power switches, electronic power switches, electrical fuses and electronic fuses; sensors and apparatus for measuring electrochemical measurement variables, namely, electrolytic conductivity, pH value and redox potential; temperature sensors, pressure sensors, flow sensors, power sensors, strain sensors; software for controlling, regulating and parameterisation of the aforesaid apparatus, instruments and equipment; apparatus for recording, transmission or reproduction of sound and images; electric and electronic indicators, loggers and recorders, namely, electronic data loggers, electronic data recorders, pressure loggers, and pressure recorders