4/4/2011 2:50 PM | |
Joined: 9/27/2006 Last visit: 6/5/2024 Posts: 12260 Rating: (2670)
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Hello pushly; You have to admit your question is quite vague. To be able to answer you we would need more information, more details. For example, what module do you plan to use for your analog channel, or are you using an integrated analog input in a S7-3xxC CPU? What kind of signal are you connecting to (4-20 mA 2-wire, 0-10 V, RTD (temperature sensor...)? In order to setup an anolg channel, you will have to insert an analog module in your HWConfig editor, which will generate the range of addresses reserved for the analog signals from this module (the analog channels of integrated analog inputs are already reserved, HWConfig will indicte the actual addresses). there is some configuration to do for each channel, choosing the type of signal and its range, the amount of required filtering... The manual Programming with Step 7 (installed on your computer with Step 7) will give you more details. The following link will let you download the S7-300 Module Data manual, which describes how the S7 CPUs handle analog signals, and describes all available analog modules (wiring, range of signals...): SIMATIC S7-300 S7-300 Module data Then in your program you will have to take the numerical value (*)provided by the analog module at the configured address (from HWConfig) and scale it so it represents engineering values (degrees C, %, gpm...). This is usually done using an existing function, FC105 "SCALE", located in the TI-S7 convertion blocks library of the program editor. There are many threads in this forum describing how to use FC105, just look for them using the Search box at the right of this page. Hope this helps, Daniel Chartier (*) Almost every analog signal that is connected to an analog input will give you a numerical value of 0-27648, or +/- 27648, once it is read into your prgram. This is described in the suggested Module Data manual above. This numerical value is proposrtionnal to the range you have setup on the channel. The exception is RTD values, which you can locate in tyhe manual. |
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