Measurement uncertainty analysis of skin moisture sensing by interdigitated electrode of capacitive method

Skin is an integral part of the human body, so skin health needs to be taken care of. One of the determinants of skin health is moisture, so an accurate measurement of skin moisture is an exciting research topic. Capacitive sensors can be used to measure skin moisture, while the geometric shape of the planar sensor is fascinating to study today. Interdigitated Electrode (IDE) is a popular sensor geometry, so sensing skin moisture with the IDE design of the capacitive method is absolutely challenging to study further, particularly since the investigation of measurement uncertainty is one of the leading indicators of sensor quality. This study aimed to analyze the measurement uncertainty of skin moisture based on the IDE of the capacitive approach. A microcontroller, capacitive sensor, screen, and proven skin moisture meter are used as the main components in realizing this research. There are four points measuring skin moisture with 90 repetitions so that a coverage factor of 2 can be used with a 95% confidence level. From the experimental results on several skin moisture measurement points, it was found that the smallest uncertainty was almost 1% at the measuring point of 30.71%. However, at the 44.71% measurement point, the most significant uncertainty value is almost 5%. The contribution of measurement uncertainty from repeatability is more dominant than the sensor reading resolution. Therefore, the measurement of skin moisture employing the capacitive method with IDE geometry can achieve an accuracy of up to 95%.