| | | Inductive displacement sensors according to the LVDT principle (Linear Variable Differential Industrial transformer) are constructed with a primary and two secondary coils, which are arranged symmetrically to the primarywinding.As ameasurementobject, a rod shaped magnetic core can be moved within the differential transformer. An electronic oscillator supplies the primary coil with an alternating current of constant frequency. The excitation is an alternating voltage with an amplitude ofafewvolts and a frequency between 1 and 10 kHz. | | Depending on the core position alternating voltages are induced in the two secondary windings. If the core is located in its "zero position", the industrial coupling of the primary to both secondary coils is equally large. Movement of the core within the magnetic field of the coil causes a higher voltage in one secondary coil and a lower voltage in the second coil. The difference between the two secondary voltages is proportional to the core displacement. Due to the differential design of the sensor, the LVDT series has an output signal which is very stable. | | |