A Smartphone-only Pulse Transit Time Monitor Based on Cardio-mechanical and Photoplethysmography Modalities

Chenxi Yang, Yudi Dong, Yingying Chen, Negar Tavassolian

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


This paper reports a system for monitoring pulse transit time (PTT). Using an Android smartphone and a customized sensing circuit, the system collects seismo-cardiogram (SCG), gyro-cardiogram (GCG), and photoplethysmogram (PPG) recordings. There is no need for any other external stand-alone systems. The SCG and GCG signals are recorded with the inertial sensors of the smartphone, while the PPG signal is recorded using a sensing circuit connected to the audio jack of the phone. The sensing circuit is battery-less, powered by the audio output of the smartphone using an energy harvester that converts audio tones into DC power. PPG waveforms are sampled via the microphone channel. A signal processing framework is developed and the system is experimentally verified on twenty healthy subjects at rest. The PTT is measured as the time difference between the aortic valve (AO) opening points in SCG or GCG and the fiducial points in PPG. The root-mean-square errors between the results from a stand-alone sensor system and the proposed system report 3.9 ms from SCG-based results and 3.4 ms from GCG-based results. The detection rates report more than 97.92% from both SCG and GCG results. This performance is comparable with stand-alone sensor nodes at a much lower cost.

Original languageEnglish (US)
JournalIEEE Transactions on Biomedical Circuits and Systems
StateAccepted/In press - 2019

All Science Journal Classification (ASJC) codes

  • Biomedical Engineering
  • Electrical and Electronic Engineering


  • gyro-cardiography (GCG)
  • photo-plethysmography (PPG)
  • pulse transit time (PTT)
  • seismo-cardiography (SCG)
  • signal processing
  • smartphone
  • wearable sensors


Dive into the research topics of 'A Smartphone-only Pulse Transit Time Monitor Based on Cardio-mechanical and Photoplethysmography Modalities'. Together they form a unique fingerprint.

Cite this