With respect to a physical magnitude, the one we measure. By varying this resistance, the output voltage will be different and that voltage will be read by the analog input of our plc. Wheatstone bridge for analog inputs in plcs certain sensors offer measurement of physical variables by varying a capacitance rather than a resistance. In this case, a capacitive bridge will be built that will follow the same philosophy as resistive bridges. It will have abilities instead of resistances though. Some of the most used sensors humidity sensor : these sensors measure the amount of water that is contained in the environment or in gases in general.
Generally this measurement is observed on the change of the capacity in a capacitor or a resistor. This capacity or resistance varies depending on the permittivity of the surrounding air. This in turn will vary with the amount of water it contains. The e commerce photo editingcapacity variation is slow, so they are not usually used for sudden changes in humidity. They are usually limited between 5% and 90% relative humidity with an accuracy of 3% for the most standard models. Temperature sensor : the most common are resistive. These vary the value of their resistance with the temperature they have. They exist in both directions, that is, they increase their resistance with temperature or they decrease it.
The most used are the ntc, ptc and rtd. They all have an exponential character, so we try to always work between their linear sections. Pressure sensor : they are based on the change in magnitude of a resistance. It will be measured on a deformable material, as the pressure of the environment increases, the shape of the surface will vary. This surface change will also modify the resistance value. It can also be calculated on a capacity. The pressure varies the length between the planoparallel plates of the condenser and varies its capacity. Weight cell : weight cells work through the