A Spray Processed Harsh Environment Humidity Sensor for Detecting Relative Humidity in Microfluidic Gas Flows
Sprache des Titels:
Proceedings of the 5th European Conference on Microfluidics
Four different custom made paints based on different compositions of carbon black (either pure or in a polyamide-imide matrix) were used to spray process a resistive type humidity sensor. The polyamide-imide composite resistors show good mechanical, chemical and high temperature stability up to 250 °C. Characterization of the resistors was done in a climatic chamber where the relative humidity was ramped from 28 to 90% and the temperature from 25 to 85 °C. The highest relative change in resistivity observed was 0.11 at a temperature of 85 °C. All tested samples showed an increase in humidity sensitivity with increasing temperature. Subsequently the temperature characteristic of the resistors was recorded up to 250 °C, where two of the tested paints showed a conversion from negative to positive temperature coefficient.