LVDT that is not an LVDT
Aaahh !

Ratiometric v Differential

5 wire ratiometeric ratio = (Va-Vb)/(Va+vb)

4 wire Differential (phase relationship)

http://www.pennyandgiles.com/getattachment/Support/Frequently-Asked-Questions/How-does-LVDT-technology-work/LVDT-Technology.pdf

Sorry for bothering you all.