Analog quantity refers to the quantity of a variable that changes continuously within a certain range, that is, it can take any value within a certain range.

For PLC, analog quantities are presented in two forms: analog input and analog output.

Our common analog input signals, such as temperature, pressure, weighing, flow, concentration, humidity, PH value (acidity and alkalinity), light intensity, displacement ranging, radar speed measurement, etc., need to transmit data to the PLC receiving signals are all called analog input signals.

The analog output signal, such as: controlling the size of the valve, controlling the frequency change of the frequency converter, etc. These control methods that require PLC to output changing signals are called analog output signals.