Siemens analog card and wire break

[muusic_man]

Hi all,
I'm not a Siemens expert (my forte is AB) and I need a little help if possible. I have a 315-2 processor and one of my input cards is a 6ES7 331-7KF02-0AB0 anaolg card. I have pressure transducers hooked up to it giving a 4-20mA input. Everything works fine. The pressure sensors are hooked to filter housings that are ocasionally removed, neccesitating unhooking the pressure transducers. What I need to do is sense the disconnect (wire break), cause the input to go high (right now it fails low) and set an alarm on my HMI. The manual for the card says that wire break only works with a PT-100. Is this true. If so then are there any thoughts on how I should go about this. If it is not true and the wire break setting for the module works for 4-20mA signals, then what should the programming in OB86 look like and how can I reference the bit that would be turned on?

Thanks in advance for any help. You folks have yet to lead me wrong and it is always appreciated.

 

[BryanG]

You don't need to use a wire break detection system, just look at the mA, if it is less than say 3mA then the the wire is disconnected. That is the whole point of 4-20mA, if the signal is less than 4mA, there is a problem.

 

[muusic_man]

You don't need to use a wire break detection system, just look at the mA, if it is less than say 3mA then the the wire is disconnected. That is the whole point of 4-20mA, if the signal is less than 4mA, there is a problem.

Thanks Bryan. I understand all that. I was hoping to use the built in stuff to do the job and maybe to have the open wire cause the plc to give a "high" output. I understand that I can do all this with code but it seems like such a cludgy way to do it if there is something designed to do that.

 

[RMA]

The input card you're using at present has no diagnostic capability. If you don't want to monitor the input value in your program then you need to use another input card such as the 6ES7331-7NF10-0AB0 (14 Bit) or 6ES7331-7KF02-0AB0 (12 Bit).

 

[muusic_man]

The input card you're using at present has no diagnostic capability. If you don't want to monitor the input value in your program then you need to use another input card such as the 6ES7331-7NF10-0AB0 (14 Bit) or 6ES7331-7KF02-0AB0 (12 Bit).

As stated in my first post the card I have is a 6ES7 331-7KF02-0AB0.

 

[KalleOlsen]

In this manual on page 221 you will find the analog over/underflow values. In the program code, you can check the PIW value and substitute if o/u -flow.

http://www.elintosprekyba.lt/library/files/S7_300_module_data_manual_en-US_en-US.pdf

Kalle