node voltage conflict
Copied from comments, so this post has an answer:


  Why have you connected those 2 conflicting points together? I can't see why it would be necessary. Just remove the wire which connects the opamp output from the 15V shifting voltage source. Leave the opamp connected to R1 &amp; R2 of course. – brhans





  Yeah that solved the problem!thanks Actually somehow I thought the negative terminal of the sensor is supposed to be connected to both parts of the circuit separately. – Sabir Moglad