The purpose of 4-20mA loops is to transmit the information from sensors that are measuring physical parameters such as temperature, flow rate, pressure, speed, etc. It is an analog signal standard where the electric current is used to proportionately represent measurements. The physical signal is converted to a current signal where typically a 4mA current represents the sensor zero level output and 20mA represents the sensor’s full scale output. Any current value in between 4 and 20mA represents a percentage in between 0% and 100%.