A domestically produced LVDT/RVDT conditioner that replaces AD698

Function replaces the domestically produced LVDT/RVDT conditioner AD698.

I. Background

With the continuous demand and development in aerospace, shipping, industrial control, and agricultural modernization across various countries, the demand and application requirements for displacement sensors are also on the rise. Moreover, the structural requirements for displacement sensors vary across different application fields. Hangjing early launched a domestically produced displacement sensor excitation demodulation circuit HJG598 to replace AD598, which has been successfully used in various assembly applications and is compatible with both five-wire and six-wire displacement sensors. Now, to fill the gap in applications for half-bridge three-wire and four-wire displacement sensors, Hangjing has combined its extensive experience in analog circuit design and application to introduce a brand new domestically produced displacement sensor excitation demodulation circuit HJG698, which can completely replace the imported device AD698.

II. Overview

HJG698 is an LVDT/RVDT excitation demodulator designed using thick film integrated technology that meets GJB2438 internal control indication requirements. It includes a square wave oscillator, a band-pass filter, and an operational amplifier with differential output functionality to generate excitation signals that drive the primary side of LVDT/RVDT. At the same time, HJG698 performs differential calculations on the amplitude-modulated wave signals output from LVDT/RVDT and converts them into DC voltage signals for output.

The excitation of HJG698 combines a square wave oscillator with a band-pass filter to filter the square wave signal into a sine wave signal. It uses a low-drift precision voltage source to power the oscillation circuit network; thus, by selecting low-temperature coefficient types for peripheral resistors and capacitors of the device's band-pass filter network, low-temperature drift sine wave signal excitation output can be achieved. A differential output amplifier with a gain of 1/1 is used as an excitation signal output to drive LVDT/RVDT so that even if there is no common ground port for LVDT/RVDT, HJG698 can still operate normally and can drive three-wire half-bridge or four-wire sensors. The subsequent demodulation part adopts a differential input structure which suppresses temperature drift of the differential excitation signal at the working principle level of the subsequent demodulation circuit, resulting in lower temperature drift of the output DC signal. It is very suitable for precision positioning and measurement applications with advantages such as low temperature drift, high detection accuracy, high reliability, and high sensitivity. It can be applied in angle position detection systems in servo control systems, aerospace, electronics, etc.

V. Absolute Maximum Ratings

Power Supply Voltage ±18V

Dissipated Power 1000mW

Operating Temperature -55℃～125℃

Storage Temperature -65℃～150℃

Lead Soldering Temperature (10s) +300℃

VI. Electrical Characteristics

Unless otherwise specified,_CC=+15V，V_EE=-15V，T_A=25℃