Generally, DCS system treats the current higher than 20.2mA or less than 3.8mA as a fault, and the pressure transducer also has fault current settings. For example, it can set the fault current of pressure transducer to 3.6mA or 22.8mA, or setting as needed and related to failure alarm setting. When the output current of pressure transducer is less than 4mA or greater than 20mA, it refers to the common saying that the instrument display is below zero or the instrument display is maximum. In this case, the fault is analyzed and judged in excess of the range. When checking the over-range fault of pressure transducer, firstly check the components related to the process, whether the process parameters have significantly changed, whether the instrument sampling valve and connecting pipes are normal, whether the connecting line or safety grille is faulty or damaged. Then check the pressure transducer itself, whether its range is selected correctly, whether the measuring diaphragm and circuit board break.