RTD vs Current analog input devices . (beckhoff to be exact )

hi . we are using beckhoff decentralised I/O module on profibus , which has its different analog cards for RTD , current and Voltage input. i need to get an 4mA-20mA input , though we had only 1 channel current input card so my supervisor gave me a 2 channel analog input card but its RTD input type. Is it safe to safe that i can't use the RTD analog input card for current measurements or i need to go through the manuals again.

2. in new TIA portal v13 i have noticed that the analog scaling blocks are a little different now. the NORM block has the input high and low range as well as the output high and low range . does that mean we don't have the to use the scaling box to scale input 0 to 1 to use NORM block to scale to physical range.

any help would be highly appreciated thanks ..

anyone any thoughts

anyone have any idea on this ?

awaisq said:

Is it safe to safe that i can't use the RTD analog input card for current measurements

Click to expand...

You can not use an RTD input card for a 4-20mA signal for any brand or model.

An RTD input card sources a constant current (typically less than 1mA) and reads the voltage drop across the RTD resistance.

A 4-20mA current source is not compatible with the actions going on in an RTD card.

With regard to question 2 scaling, I have no idea.

Thank you!!

The older scale and unscale blocks are still there, you just have to look for them. There should be a menu/folder somewhere near the norm and new scale instruction blocks where you can find the older blocks to use in your program. If you can't find them, I can look at my laptop with TIA on mon.

yea , i just need to scale an input giving input low/high and output low/high variables. so if the new norm block just does the same thing its better . but i don't understand why is there also a scale block then.

awaisq said:

yea , i just need to scale an input giving input low/high and output low/high variables. so if the new norm block just does the same thing its better . but i don't understand why is there also a scale block then.

Click to expand...

maybe for backward compatibility?

i just saw again .there is no NORM_X or SCALE_X block in TIA portal v13 . just the new NORM and SCALE .

just for confirmation. The new NORM block just works fine without the scaling block, just just to convert the input int to dint and the real first .

What PLC are you using? I'm pretty sure I just used the old scale block less than a week ago with an S7-1500.

when i used it with the S7300 it didn't show. yesterday i was working with S71200 and there were just these Scale_x and Norm_x . the new blocks i had found in PID somewhere dosn't showed when i used S71200 . that was a bit confusing.

Here's a screenshot of the instructions window in a project using an S7-1500. Scale and Unscale are under the "Others" folder.

#1 with a relay it is possible to look at two 4-20 mA signals, slowly but it works.
it must be close before break, to avoid alamrs from the card.
what is the typenumber on the cards?