12/17/2015 12:23 PM | |
Joined: 3/23/2014 Last visit: 11/2/2022 Posts: 10 Rating:
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hello mr this is a good question but may i know why need output (0...10 )V ? |
12/17/2015 8:17 PM | |
Joined: 9/27/2006 Last visit: 9/4/2024 Posts: 12282 Rating:
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Hello mirip; The pulse output of a water counter will generally give you a measure of volume (liters, for example).Is that the case in your project. Whereas a "regular" (analog of fieldbus) flowmeter should give you a measure of flow (liters per minute). Is this the type of signal your 0-10V would provide to your PLC? Therefore you must make sure that the value in volts expected by the PLC corresponds to the control range that it will use to make its decisions for its flow control. Supposing this is the case for you (and as suggested earlier by mindware), you should first determine the flow value from the pulse output of your water counter. (count the number of pulses in a period of time useful for the application). Use a timer instruction to determine the period of pulse counting, repeat cyclically and use a counter to count the pulses (a slow count, under 10 kHz) can be handled by a regular UP counter, if it is faster then look up HSC instructions.). Next you should scale the flow value so that the output signal (which will be sent to the analog output module) will represent a corresponding fraction of the full-scale value your controller is expecting. If your maximum possible value is 30l/min (that would correspond to the 10V analog output), and your actual pulse count corresponds to 15 l/min (after you have counted the pulses in a minute), then you have a scaled value of 50% and you would generate an analog output of 5V to your analog output. The PLC would then decide whether to open or close the valve or pump that controls the flow. Depending on the PLC family you would use the instruction sets are different. If you plan on programming a S7-200 I would suggest you look at the S7-200 system manual for the Timer, counter and HSC (if needed) instructions available: https://support.industry.siemens.com/cs/ww/en/view/1109582 For the scaling operation I would have you look at the following FAQ (in conjunction with the system manual): How can you scale analog values with S7-200 in conjunction with CPU224XP and expansion modules EM 231, EM 232 and EM 235? https://support.industry.siemens.com/cs/ww/en/view/27043396 Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 12/17/2015 8:24:10 PM |
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12/22/2015 7:16 PM | |
Joined: 4/9/2010 Last visit: 8/30/2024 Posts: 225 Rating:
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If I understand correctly, 600 L/min or 10 L/s will result in maximum 10Hz signal so this simple program should do the trick. LD I0.0 // Pulse input from the flow meter As an alternative, you could use a frequency to current/voltage converter like the one in the enclosed pdf file. Cheers, Adam Attachment8581180000_WAS4_PRO_Freq_en.pdf (325 Downloads) |
Last edited by: adam_ski at: 12/23/2015 1:36:14 PM |
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