Title: Multiply and Filter: An Universal Measurement Trick


Arijit Sinharay, Tata Consultancy, India 


This tutorial focuses on discussing very fundamental measurement trick to apply as a Swiss-knife for developing various sensors while guaranteeing maximum signal to noise ratio. The principle is based on multiplying (with a reference excitation) and filtering which will be discussed in detailed along with various use -cases and examples. Formally, this technique is termed as Lock-in detection in Physics/Instrumentation Labs, Homodyne or Heterodyne receivers in communication and Zoomed FFT in Signal Processing areas. This tutorial will bring out the basic structure from all its variants and point out specific benefits of using this technique over usual measurement scenarios. Moreover, this tutorial will show how easily this technique can be used to develop various sensors and sensitive measurement instruments. For example, we will discuss how to build a very sensitive directional flow meter, vibration detector, CW Radar, Ultrasound Doppler, non-contact eye-blink detector, Frequency Response Analyzer to name a few. In addition, it would be discussed how high frequency resonance spectroscopy (in MHz range) can be done on standard smartphones utilizing this technique. Finally, the tutorial will outline how to build such system with affordable off-the-shelf electronics components.