Ambient light cancellation in photoplethysmogram application using alternating sampling and charge redistribution technique.

To overcome a large DC offset, ambient light interference, and optical path variation, a robust PPG readout chip is fabricated using 0.13-µm CMOS process. Against the large DC offset, a saturation detection and current feedback method can compensate a current of up to 30 µA. To be robust against optical path variation, an automatic emitting light compensation method is adopted. To remove the ambient light interference, we propose an alternating sampling and charge redistribution technique, in which no additional power is consumed, and only three differential switches and one capacitor are required. The PPG readout channel consumes 26 µW and has a input referred current noise of 260 pArms.

Exercise amount calculation using a wearable half-cell potential sensor for mobile aerobic exercise management.

The obesity has grown to concerning proportions in recent years, and it causes heart disease, type 2 diabetes, breast cancer, and colon cancer. To get healthy weight, commercial wearable devices with a accelerometer have been released to help users to quantitatively manage calories. However, an accelerometer has disadvantages: large power consumption and expensive price. We suggested a new method to measure the exercise amount using a HCP sensor. We performed an experiment to compare accuracies of exercise amount estimation using a HCP sensor with using an accelerometer with five subjects, and the accuracy of the HCP sensor was comparable to it of the accelerometer. Since a HCP sensor has lower power consumption and cheaper price than an accelerometer, wearable sensor can be smaller and cheaper than current commercial devices.

Motion artifact reduction in electrocardiogram using adaptive filtering based on half cell potential monitoring.

The electrocardiogram (ECG) is the main measurement parameter for effectively diagnosing chronic disease and guiding cardio-fitness therapy. ECGs contaminated by noise or artifacts disrupt the normal functioning of the automatic analysis algorithm. The objective of this study is to evaluate a method of measuring the HCP variation in motion artifacts through direct monitoring. The proposed wearable sensing device has two channels. One channel is used to measure the ECG through a differential amplifier. The other is for monitoring motion artifacts using the modified electrode and the same differential amplifier. Noise reduction was performed using adaptive filtering, based on a reference signal highly correlated with it. Direct measurement of HCP variations can eliminate the need for additional sensors.