4/23/2015 11:19 AM | |
Joined: 1/21/2013 Last visit: 9/4/2024 Posts: 4620 Rating: (707) |
Hello mbt2412, Please have a look: Scaling and Unscaling Analog Values - Siemens Trouble with 4-20mA scale - Entries - Siemens Industry Online ...
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4/23/2015 12:37 PM | |
Joined: 6/24/2013 Last visit: 9/20/2024 Posts: 1628 Rating: (421) |
Hi When module is configured to 4..20mA (observe 2wire / 4wire for analog input and do not forget to adjust range plug on analog input module itself (if present)) values are: 0 = 4mA ... 27648 = 20mA 32767 = ERROR -32768 = ERROR When inoput is a bit less than 4mA module returns a negative value let's say between -1000 and 0 You can use attached block instead of Siemens SCALE block - it covers over range and gives debounced out of range alarm. In a nutshell: Let's say You convert a volt meter signal which has range of 1000V(0..1000V --> 4..20mA) Configure analog module: - sensor has its own supply: 4 wire 4..20mA - sensor is powered from PLC (loop powered): 2 wire 4..20mA Call SCALE with Input: Your PIW Address Low Limit: 0.0 // 0V High Limit: 1000.0 // 1000.0V Mode: False (Unipolar) Output: a REAL variable [V] Let's say You sent RPM to drive as analog output: 4..20mA --> 0..10000RPM Configure output to 4..20mA Call UNSCALE with A Real Variable [in RPM] Low Limit: 0 High Limit: 10000.0 Output: Your PQW Address Output will behave: 0 = output 4mA; 27648: output 20mA Hope this helps. AttachmentFC105.pdf (2533 Downloads) |
4/23/2015 2:51 PM | |
Joined: 6/24/2013 Last visit: 9/20/2024 Posts: 1628 Rating: (421) |
Hi The of block was written in STL to optimize speed and it is not convertable to LAD for example when You use trick: L #A // Tested Variable L #Limit // Max Allowed Value >=I // A>=Max Allowed Value? JC AWRI // YES? Jump to Write (write limit) POP // NO: Move A to ACC T #B // Write A capped to the limit Attached here as .zipped AWL (source) file. To use You need 1. extract .zip 2. import it to STEP 7 Sources 3. add symbol FC105 SCALE in symbol table 4. Compile Source 5. substitute reference to 100ms tick to Your own 100ms pulse. Regards Piotr AttachmentFC105.zip (1538 Downloads) |
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