how to connect 4 wire RTD (PT100) in wheatStone Bridge? 6

[ak05]

i want to connect a 4 wire RTD PT100 in a wheatStone Bridge.
i tried searching on internet but only upto 3 wire configurations in bridge are available or circuits using other ADS IC's are available. but i want to do it in a Bridge Configuration. can any one suggest how i can do it?

 

[ScottyUK]

Have a read of Analog Devices' application note:

http://www.analog.com/static/imported-files/seminars_webcasts/49470200sscsect2.PDF

4-wire connection is for use with a Kelvin connection. 3-wire is used for a bridge with one varying element.

 

[ak05]

hey Scotty , nice link...i read on it.. but in the kelvin Section they have not given about which element is varrying and all , means in case i am connecting a 4 wire RTD in that kelvin section how the circuit will look like? can u please tell me?
the ckt is this :

 

[ak05]

 

[ak05]

@skottyUk i meant where is the location of the 4 wire RTD in that circuit?

 

[IRstuff]

"i meant where is the location of the 4 wire RTD in that circuit?"

Did you not read the Wikipedia article you quoted? You solve the loop equations for wherever you put the RTD.

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[ak05]

@IRstuff
m asking about the position of the RTD in this Configuration. not the wiki one.
see below link

where is the location of the 4 wire RTD?

 

[ScottyUK]

That circuit would use a 2-wire RTD, and it would not compensate for lead resistance. There is no way to deploy a 4-wire RTD in that circuit. You could make a 2-wire RTD from a 4-wire type if you wanted to. Just be careful to cut one lead off each end, not both leads off the same end. ;-)

 

[IRstuff]

"where is the location of the 4 wire RTD?"

You again show a bridge, so again, you put it in and solve the equations. And again, you can only use two leads for the circuit you show.

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[itsmoked]

Now you're asking for an IC that can accept 4 wire RTDs.. They're not cheap! I gave you a link to an IC that avoids you needing any other ICs and minimizes the code math.

What class IS this for?

Keith Cress
kcress -

http://www.flaminsystems.com