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HOW to choose a wrong Real value

Created by: Automation_lover at: 9/30/2022 10:40 AM (8 Replies)

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9/30/2022 10:40 AM	Rate (0)
Automation_lover Member Joined: 4/15/2022 Last visit: 9/18/2025 Posts: 28 Rating: (0)	Hi guys! For a powerpoint presentation, I have to describe the instructions / logic blocks (timers, comparators, etc.) that are in the Ladder Diagram. Is there a way to highlight the instruction ``Check validity`` when the condition it`s not meet? I mean, when the real value it`s ok, i see, the result of RLO is 1 logic, but how can i introduce a wrong value that return 0 logic at output? To mention that i work with PLCSIM 15.1. Thank you! Attachment TIA OK.png (313 Downloads)

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9/30/2022 6:14 PM	Rate (1)
jacek d Platinum Expert Joined: 9/23/2005 Last visit: 9/26/2025 Posts: 5122 Rating: (768)	Write to MD100 a bit string which is invalid real number. Like NaN. BTW, real numbers should be properly named as IEEE754 floating point numbers. Just to give you starting point while googling.
	Regards, Jacek What is confusing you is the fact that you never see a number but always its digit representation. So you end up thinking that the number is the representation. - Andrej Bauer Any claims against me - based on whatever legal reason - resulting from the use of any code and/or ideas presented on this forum shall be excluded. #StayWithUkraine
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This contribution was helpful to 1 thankful Users 0_Einstein

10/1/2022 8:33 PM	Rate (0)
Automation_lover Member Joined: 4/15/2022 Last visit: 9/18/2025 Posts: 28 Rating: (0)	Thx! But how can I make this bit string? And with what instruction to move that string into my floating number? with a move instruction?

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10/3/2022 7:34 AM	Rate (0)
jacek d Platinum Expert Joined: 9/23/2005 Last visit: 9/26/2025 Posts: 5122 Rating: (768)	Urs_Petru But how can I make this bit string? If you google you will find it. It is well-known. Or you can use a tool like this one. Urs_Petru And with what instruction to move that string into my floating number? with a move instruction? Yes.
	Regards, Jacek What is confusing you is the fact that you never see a number but always its digit representation. So you end up thinking that the number is the representation. - Andrej Bauer Any claims against me - based on whatever legal reason - resulting from the use of any code and/or ideas presented on this forum shall be excluded. #StayWithUkraine
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This contribution was helpful to 1 thankful Users BoletusEdulis

10/6/2022 11:06 AM	Rate (0)
Automation_lover Member Joined: 4/15/2022 Last visit: 9/18/2025 Posts: 28 Rating: (0)	Look, I found a easier way to do that. If you apply a negative number at the input of an SQRT instruction, it gives back an invalid floating number. Attachment Ok instruction.png (278 Downloads)

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10/6/2022 6:09 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 9/26/2025 Posts: 16149 Rating: (2516)	Shouldn't SQRT calls be immediately preceded by ---[>=]--- comparison with 0.0? Urs_Petru Look, I found a easier way to do that. If you apply a negative number at the input of an SQRT instruction, it gives back an invalid floating number.
	science guy
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10/7/2022 11:46 AM	Rate (0)
Automation_lover Member Joined: 4/15/2022 Last visit: 9/18/2025 Posts: 28 Rating: (0)	I think so, but in this case wasn't about making a usable function. Was just to highlight the ability of the OK instruction to stop the RLO if the floating number it's incorrect.

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10/7/2022 12:48 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 9/26/2025 Posts: 16149 Rating: (2516)	Hmm, would it be simpler to either capture the error with a ---(/)--- at the ENO of the instruction and write nothing else in the rest of the network where it is possible an instruction could generate an error? I think preventing (which enables detecting) errors is better than allowing them and then only processing if everything is acceptable. However, I get your point about figuring out a use of the OK instruction, but that isn't the title of this topic. Urs_Petru I think so, but in this case wasn't about making a usable function. Was just to highlight the ability of the OK instruction to stop the RLO if the floating number it's incorrect.
	science guy
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10/7/2022 12:56 PM	Rate (0)
jacek d Platinum Expert Joined: 9/23/2005 Last visit: 9/26/2025 Posts: 5122 Rating: (768)	Urs_Petru Look, I found a easier way to do that. OT. Taking easier ways usually do not build any expertise.
	Regards, Jacek What is confusing you is the fact that you never see a number but always its digit representation. So you end up thinking that the number is the representation. - Andrej Bauer Any claims against me - based on whatever legal reason - resulting from the use of any code and/or ideas presented on this forum shall be excluded. #StayWithUkraine
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