HJG698 LVDT/RVDT Excitation and Demodulation Unit

HJG698 is an LVDT/RVDT excitation and demodulation module designed using a thick-film integrated circuit process that complies with the internal control requirements of GJB 2438. It incorporates a square‑wave oscillator, a bandpass filter, and a differential‑output operational amplifier to generate the excitation signal that drives the primary winding of the LVDT/RVDT. Simultaneously, HJG698 performs differential processing on the amplitude‑modulated output signal from the LVDT/RVDT and converts it into a DC voltage output. The excitation circuit of HJG698 employs a combination of a square‑wave oscillator and a bandpass filter, filtering the square wave into a sinusoidal waveform. A low‑drift precision voltage source powers the oscillator network; consequently, by selecting low‑temperature‑coefficient resistors and capacitors for the peripheral components of the bandpass filter, a sinusoidal output with minimal temperature drift can be achieved. A differential‑gain‑of‑1 output amplifier is used to drive the LVDT/RVDT with the excitation signal, enabling normal operation even when the LVDT/RVDT lacks a common ground terminal, thus supporting three‑wire half‑bridge or four‑wire sensors. The subsequent demodulation stage adopts a differential input configuration, which inherently suppresses the temperature drift of the differential excitation signal in the downstream demodulation circuitry, resulting in reduced temperature‑induced drift in the output DC signal. This makes HJG698 ideally suited for high‑precision industrial position and metrology applications, offering advantages such as low temperature drift, high measurement accuracy, excellent reliability, and high sensitivity. It is widely employed in angular‑position sensing systems across servo control, aerospace, electronics, and other fields.

HJG698 LVDT/RVDT Excitation and Demodulation Unit

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