siemens im151 thermocouple open circuit??

mr_sleepy · Mar 21, 2011

Hi all. Just a quick question with perhaps an obvious answer (hopefully). I have an im151 basic head module with a 2ai tc hf card attached to it. I have the card addressed properly and i have the values coming back to the plc where i expect them to which is fine. The problem i have is when the thermocouple is disconnected the value floats instead of defaulting to 32648 or 0 or whatever. This is a problem because there is alarms attached to each of the tc's and they trigger on and off and fill up the alarm history buffer in 2-3 mins time which voids the purpose of it. The question is how do i get the value to stabilise when the card is open circuit or detect that there is a problem so i can disable the alarm etc. Thanks in advance.

krk · Mar 21, 2011

Check your PMs.

mr_sleepy · Mar 21, 2011

PM's?

Jeff23spl · Mar 21, 2011

Private Messages

But is the connection can be loose? when i got problems like that with an RTD, their is 99% of the time a loose connection somewhere

PLC · Mar 21, 2011

Private mail

What part number is the tc module?

mr_sleepy · Mar 21, 2011

The part number of the unit is 6es7 134-4nb01-0ab0. I checked the options in the hwconfig, there is a checkbox for wire break diagnostics but i have no idea how to use it. I guess if i could detect that condition that would be ideal. We use omron plc kit as well but we never have any issues with their tc cards. If you get short,open or no circuit then the value auto defaults to overflow and it is stable at that. Hopefully the solution isnt too long winded for siemens as there is a lot of alarms and tc's on this project.

PLC · Mar 21, 2011

when you enable - wire break/diagnstics
I believe OB82 is called, Check out this manual and the diagnostics chapter
This should put you on track

https://support.automation.siemens....fo&lang=en&objid=6ES71344NB010AB0&caller=view

mr_sleepy · Mar 22, 2011

Hi all i eventually found the solution after a bit more playing around today. Seems i didnt tick all the boxs that were required. I Have included a picture that shows the 2 boxs i didnt check for reference. Incase anyone else stumbles across this once you tick those 2 boxs you then get the diagnostics info back in ob82 but for my purpose what also happens is that when you get an open or short circuit in the thermocouple it defaults to overflow or 32768 which in my application triggers a danger alarm and prevents overheating.

Thanks again.

mr_sleepy · Mar 22, 2011

Oops ,seems like my picture didnt work on the previous post. Here it is this time but as an attachment.

danw · Mar 22, 2011

Thank you for making the effort to post a follow-up after you solved your problem. Your screen shot might be of assistance to any number of people down the road.

Dan

mr_sleepy · Mar 26, 2011

No Problem

atifshm · May 22, 2012

no problem

shooter · May 22, 2012

A very high resistor like 5 Mohm over the contacts is doing a good job for this. as well as other volt inputs, like mV or RTD.

siemens im151 thermocouple open circuit??

mr_sleepy

Member

krk

Lifetime Supporting Member

mr_sleepy

Member

Jeff23spl

Member

PLC

Member

mr_sleepy

Member

PLC

Member

mr_sleepy

Member

mr_sleepy

Member

danw

Lifetime Supporting Member

mr_sleepy

Member

atifshm

Member

shooter

Member

Similar Topics