LVDT : Residual voltage may be on account of I/P supply voltage and also due to harmonics produced in the o/p voltage on account of use of iron core.
An incomplete magnetic or electrical unbalance or both which result in a finite O/P voltage at the null position. This finite residual voltage is generally less than 1% of the max. o/p voltage in the linear range. Other causes of residual voltage are stray magnetic fields and temperature effects.
Applications : LVDT is used as a secondary transducer as it can be used as a device to measure force, weight and pressure etc. The force measurement can be done by using a load cell as the primary transducer while fluid pressure can be measured by using Bourdon tube which acts as primary transducer. The force or the pressure is converted into a voltage. In these applications the high sensitivity of LVDTs is a major attraction.