LVDT Sensor Modeling and Signal Conditioning Design

ABSTRACT

This presentation shows how the VHDL-AMS modeling language can be used to model a “multi-physics” sensor component: A Linear Variable Differential Transformer (LVDT). The model is based on fundamental textbook equations, but it can be characterized to match actual LVDT datasheet specifications. This model is then used to analyze performance trade-offs for various analog and digital signal conditioning circuits and algorithms. These include an analog rectifier/low-pass filter, a digital phase demodulation method, as well as the unique ratiometric algorithm of a commercial AD598 LVDT Signal Conditioning IC. Simulation is used to quantify the degradation effects of a long cable run, between the sensor and the conditioning circuit. Temperature variations cause the cable resistance to change, which generally leads to position measurement errors. Parametric analysis techniques are used to identify the design that is most effective at mitigating these environmental disturbance errors.