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. Author manuscript; available in PMC: 2022 Feb 18.
Published in final edited form as: IEEE Trans Biomed Eng. 2020 Feb 28;67(11):3134–3140. doi: 10.1109/TBME.2020.2976989

Fig. 1.

Fig. 1.

Measurement devices to investigate the impact of photo-plethysmography (PPG) sensor contact pressure (CP) on pulse arrival time (PAT). A custom device comprising a reflectance-mode PPG sensor and load cell housed within a 3D-printed structure was built to measure the finger PPG waveform and CP. This device was accompanied by a visual guidance tool for slowly increasing the CP over a wide range. Commercial devices were used to measure the ECG waveform as well as the finger BP (F-BP) waveform. PAT could then be detected as the time delay between the ECG and finger PPG waveforms at different levels of CP.