Temperature transmitter

[Saffa]

I then remind myself that there's a difference between good questions that seek information, like this thread I think, and lazy twits saying "I'm in a hurry - whats the answer to problem 23?"

I think that's very true and I was probably a little harsh on the OP. Too many other terrible posts like "I have 20 power meter, how do I build energy monitoring system?" read just before this one!

PS - Aeration Control System Design is a brilliant reference. It's opened my eyes to several possible optimization opportunities at our largest plant that I'd never even thought about before!

 

[Tom Jenkins]

Thanks for the compliment on the book - I appreciate knowing it has been helpful!

 

[gigacer]

thanks to all for your replies, i know now how to do it

 

[gigacer]

hi, again me, i tried to connect temperature transmitter with PLC, i have use the SM331 module and FC105 block to scale input, but when i connect it all and when i run program in the PLC, i dont get any output of the block FC105, in this picture http://www.igreklik.com/slike/images/20537055351926301736.png you can see how i wired it and how i use the FC105 block, is the wiring ok, what i'm a doing wrong?

 

[danw]

Your transmitter is not powered.

Here's a generic diagram of what you need to do:

And an edited version of what you posted:

-

 

[gigacer]

thank you, but why C here? isn't this a 2-wire transducer?

 

[danw]

My oversight error. I edited a graphic from the web to show the wiring.

The switch position should be the letter D.

 

[gigacer]

ok, thanks again

 

[osmanmom]

Danw something missing on the configuration

 

[osmanmom]

check this

 

[gigacer]

so it's has to be C after all?

 

[danw]

If the statement above applies to the Siemens card being used, then a 2 wire becomes a 4 wire transmitter.

The industry definition of 2 wire vs 4 wire does not include the source of the DC power supply, but apparently it makes a difference for a Siemens analog input. It's their input card so you gotta play by their rules.

 

[gigacer]

hi, i succeeded to get the value from the temperature transmitter , now i need to connect another pt100 sensor to SM331 module, i don't have temperature transmitter for this sensor and i need to connect it directly to SM331 module, i have read on internet about wiring pt100 sensor with a 4-wire connection and i draw on this picture how i think it should be wired with a SM331 module.

Is this wiring ok, or i need to wire it differently ?
Are this blocks for scaling ok, is this scaling gonna work this way?

 

[danw]

Earlier you stated, "S7-300 PLC has a SM331 module (4-20 mA analog input)", so that card clearly can hancle a 4-20mA signal.

But a 4-20mA signal is a modulating current signal; an RTD is a resistor with positive temperature coefficient which needs an excitation current.

Why do you think that your particular board is compatible with an RTD? Does it have excitation current? Is there a wiring diagram showing an RTD connection to that specific board?

 

[gigacer]

this module is compactible with voltage, current, resistor and temperature, you have it all in this manual

Here's the pt100 part: