PLC analog input input is a powerful reason - Database & Sql Blog Articles

Filter 18.432M

1. You may be using a self-powered sensor or use two separate power supplies for the CPU's extended analog input modules and sensors. There is no interconnection between the grounds of the two power supplies. This results in a high fluctuating common mode voltage that affects the value of the analog input.
2. Another reason may be that the cable on the analog module input is too long or poorly insulated.
Remedy:
1. Connect the terminal M of the analog module to the corresponding terminal of the sensor to compensate for these changes.
Precautions:
Make sure in advance that there is only one connection between the two power supplies. If other connections already exist, an undesired compensation current can occur when adding a block connection!
background knowledge:
The analog input module does not perform potential separation.
The common mode voltage cannot be greater than 12V.
Common mode rejection is 40 dB at 60 Hz.
2. Utilize analog input filter:
In Micro/Win "View> Systemdatamodule>Tab:Analoginputfilter".
Select the analog input to be filtered.
Select "Numberofqueries" and "DeadTime".
The "Numberofqueries" field contains the number of queries by which the current average of several output values ​​can be calculated.
This value is calculated from the last n values, where n is the value in "Numberofqueries".
The dead time determines the maximum allowable offset from the average.