ASIC Based LVDT Signal Conditioner for High-Accuracy Measurements

Abstract

A novel Application-Specific Integrated Circuit (ASIC) based signal conditioning system for closed loop control of Linear Variable Differential Transformer (LVDT) for sensor interface application is presented in this paper. The LVDTs are used for measuring linear displacement in industrial, military, aerospace, sub-sea, downhole drilling, nuclear power and process control applications. The signal conditioning is achieved through an ASIC-based digital signal processing unit. The existing commercially available Integrated Circuits (ICs) for LVDT signal conditioning are mostly analog and additional external circuitry is required for processing. The proposed system is a digital implementation of the LVDT signal conditioner with a better dynamic response and linearity through closed loop control. A unique feature of this ASIC is the use of synchronous demodulation technique using ADC sampling, reducing the complexity involved in conventional AM demodulation circuits. One of the major advantages of digital implementation is that the system can be reconfigured through external supervisory control. In this implementation, this is enabled by a universal asynchronous receiver-transmitter (UART) interface. This makes the system suitable for a wide range of applications. The functionality of the system was verified through a Verilog implementation on ARTIX-7 Field Programmable Gate Array (FPGA). The ASIC design is implemented in SCL-180 nm technology with an area 1 mm X 1 mm and the power utilization is 285 \(\upmu \)W.