Transabdominal fetal pulse oximeter using LEDs and photodiode: A design consideration study

This paper presents a design consideration study of portable light detection components to be applied in the transabdominal fetal pulse oximeter. Several limitations are found in the previous fetal oximeter sensors. The sensors are either suitable to be used for invasive technique, high-power dependent or bulky in size. The selection of the light source is considered based on several parameters such as wavelength, angle of half intensity, power dissipation and cost. Meanwhile the selection of light detector is depends on the active area, electrical-optical characteristics, photodetector noise and cost. An instrumentation system setup utilizes the chosen sensors has been developed. In order to evaluate the capability of the proposed sensors, two measurements are done based on the sensors modes arrangement; transmission and reflectance. The preliminary results show that the developed system is able to measure the PPG signals in two different modes. From the experiment observation, the current limit resistor and the emitter-detector spacing are the two pertinent parameters that affect the operation modes of the proposed sensors.