Use a DAC to vary LVDT excitation

摘要

LVDTs (linear variable differential transformers) are electromechanical measuring devices that convert the position of a magnetic core into electrical signals. You generate these signals via excitation on the primary side. The results on the secondary side—typically, two secondary windings—depend on the position of the core (Figure 1). The excitation typically ranges in amplitude from 1 to 10V and in frequency from 1 to 10 kHz, depending on the type of LVDT you employ. Traditionally, for one circuit to provide such variability in frequency and amplitude, you can use either an LC tank with adjustable components or a sine-wave generator under microcontroller control. It can be difficult to achieve precision over time and temperature with the LC-tank circuit because of variations in passive components.