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10 PID steam control loops in s7 1200 CPU

Created by: karkas at: 9/9/2014 7:32 PM (3 Replies)

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9/9/2014 7:32 PM	Rate (0)
karkas Posts: 54 Rating: (0)	Good afternoon, I have been requested to submit a service offer for 10 PID steam control loops and the only inmediate option we have is to use a S7 1200 CPU (say 1214), not a chance of using a S7 315 or better, at least soon. But I couldn't find in the manuals how many PID blocks can one of them implement, or if it is possible to implemment 10 or more in one 1200 CPU, how many can they handle efficiently? Thanks in advance.
karkas Posts: 54 Rating: (0)	Last edited by: karkas at: 9/9/2014 7:35 PM
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9/10/2014 7:13 AM	Rate (0)
amsd Experienced Member Joined: 7/8/2012 Last visit: 12/13/2024 Posts: 40 Rating: (0)	Hello, Please find on following link /tf/WW/en/Posts/39741
	Last edited by: amsd at: 9/10/2014 7:15 AM
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9/10/2014 2:55 PM	Rate (1)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/17/2025 Posts: 15541 Rating: (2465)	karkas Good afternoon, I have been requested to submit a service offer for 10 PID steam control loops and the only inmediate option we have is to use a S7 1200 CPU (say 1214), not a chance of using a S7 315 or better, at least soon. But I couldn't find in the manuals how many PID blocks can one of them implement, or if it is possible to implemment 10 or more in one 1200 CPU, how many can they handle efficiently? Thanks in advance. Did not follow the provided link from prior post. The real question is how fast do your loops need to respond and how fast can they realistically respond? For example, if your control actuators take seconds to move from full off to full on (or open to closed), having a plc update every 5 ms your PID control is not really helpful so set it to say 50 or 100ms. If the PID controls are all in the 100ms response range, you can do quite a few PID controls until you run out of plc memory and processing capacity. However, if your hardware can respond very quickly, 10 PIDs may make the choice for the s7-1217 over the s7-1211/1212 more compelling. If you are also selecting the Firmware 4.0 hardware, that will also help determine if it will work. Knowing most steam controls are relatively slow, I would say a s7-1200 could handle it just fine with perhaps 20-40 ms cyclic update rates for the individual pid controls. Just make sure they are phased so they do not all try to activate at exactly the same time, which might result in a very long single scan time.
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9/21/2014 5:30 AM	Rate (0)
natenut Posts: 33 Rating: (7)	when the s7-1200 first came out the "s7-1200 transistion manualA5E02486860-01" stated that the 1214C could control 16 PID loops. i have not seen anywhere else where this information is. However, it seems you can make projects with more than 16 PID technology objects.
natenut Posts: 33 Rating: (7)
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