Guys sorry to ask another question , please see the following picture, the output of my Wheatstone bridge is zero since all R equal, after line followers, it still zero, but in the last stage there something goes wrong and i get 5.64 v why is that ????

 

You cannot reference R8 to 0V; it must be referenced to a voltage near half way between 0V and 12V. Or, the amplifier on the right must be operated on split supplies.

 

Also your opamps seem to have their power supply reversed.

 

If those are LM324 op amps then you should be able to operate at 0V output but the unbalanced bridge output must only generate an output polarity such as to generate a positive output at U2.

So your main problem is incorrect op amp power polarity as Kubeek noted.

 

You cannot reference R8 to 0V; it must be referenced to a voltage near half way between 0V and 12V. Or, the amplifier on the right must be operated on split supplies.

i Did both of your suggestion, but still its not working, one more thing, i am just wondering why i cant operate the last amp from the right on single source, and i need to add virtual ground or split them,
the data sheet of that particular amp says that its possible to operate from one source
Many thanks for help


Update, thanks all for that excellent help, manged to make it work, the polarity in last amp in the second trail were wrong again, thanks all.....million thanks.

 

You cannot reference R8 to 0V; it must be referenced to a voltage near half way between 0V and 12V. Or, the amplifier on the right must be operated on split supplies.

Hello mike, i am just wondering mike, you said that the amp on the right should not be referenced to 0, and i should split or use virtual ground, well you were right, the circuit worked only after i did this
what is the cause of that, even though that the amp doesn't require split input

Thanks a lot

 

Just a note. In TINA, you can reorient your op amps so that + is on top by right clicking the symbol and selecting rotate and/or mirror as required. That will help avoid errors like a reversed supply. I don't know why the symbols are oriented like that but that's how you fix them.
Good luck.

 

As long as you don't try to output a negative voltage from U2, then you should be able to operate with a single supply and no split ground.
Your circuit shows the VM1 voltage from the bridge as being positive, which will try to generate a negative voltage at U2's output.
That may be your problem.