LVDTs are also made in rotary models . Its core has specially shaped iron from it is shown in fig linear output is possible for only +/- 40 degree. Thus angular displacement can be measured. It has sensitivity of 10 to 20 mv per degree. The operation of RVDT is similar to that of an LVDT. At the null position of the core, output voltage of secondary winding S1 and S2 are equal and in opposite thus net output is zero. Any rotary motion from null position will result in differential voltage output .The greater this angular or rotary displacement, greater will be differential output hence response of transducer is linear. Clockwise rotation produces an increasing voltage of secondary voltage of one phase while counterclockwise rotation produces an increasing voltage of opposite phase hence the amount of angular displacement and its direction may be ascertained from the magnitude and phase of output voltage of transducer.