Widely sensitive optical humidity module by using acrylic resin and a position sensitivity detector

Humidity sensor module fabricated using acrylic resin and PSD (position sensitivity detector). In order to directly convert to electrical signal from output signal of optical humidity sensor system consisted of a light source, a gap, and an acrylic resin film coated on PSD. For the purpose of convert to 4–20 mA signal from current change according to the relative humidity (RH) integrated amplification of output current and 4–20 mA module by a 0.8 µm analog mixed CMOS process. Using the fabricated humidity sensor and Pt-100 accomplished one-bodied temperature-humidity sensor module and tested. The experimental results show that the sensitivity and linearity of sensor get better, while the thickness of the acrylic resin film is increased. The linearity of RH-current characteristics is good in the measuring range from 10 to 90% at 15 °C. The sensitivity of this sensor is 6.52–7.34μA/% RH. Furthermore, the current at PSD is measured with the rise and drop of RH, and the four times repetition is also recorded, which all demonstrate the good stability and repeatability of our proposed structure.