Use of 4 floating current sources

[akaliuseheal]

Homework Statement

I have 4 resistive sensors thus I need to tie 4 floating current sources. Floating current source will give me output voltage linear to the resistance of a sensor. I know it is not the best solution but it is good enough.

Image provided:

Homework Equations

None

The Attempt at a Solution

I did it by aligning them one under another and tying Vref into one point but I am confused by the fact there is no ground.

 

[BvU]

there is no ground

What is the little horizontal line at the bottom end of R_s ?