How to handle input module plc plc signal

PLC analog input module to analog ( continuous signal ) is converted to digital ( discrete signal ) usually after : sampling and quantization two processes. For example, "analog" is the distance from the PLC Programmable industrial controller plc origin of moving objects , " sampling " is equivalent with a camera shooting, at regular intervals on the " capture " a picture , as long as a suitable interval , the picture is also through these intermittent energy about the trajectory of the object. " Quantify " the process is to put these photos in various locations of objects are classified into a limited number of specified location , such as 1 meter , five meters , 10 meters ..... , namely the continuous position data . " format " ( converted to CPU can recognize and handle data format ) , to facilitate the next step of CPU processing . Siemens S7-300PLC for example , 0-20mA input corresponds to 0-27648 , namely PLC internal " 1" represents (20/27648) mA; corresponds to the input of  PLC Power supply module plc 5mA, internal PLC is represented by 6912 .
After the analog to digital conversion , the PLC can be carried out in a variety of digital processing ( including math, logic operation ) , according to the practical application of specific processes identified . For example , determining a first analog input channels of digital value is greater than 6912 ( corresponding to 5mA), meet the conditions , the output of a switch or a digital computing . If necessary you can also go through the digital analog output module ( inverse process) an analog output .