What type of humidity sensor is used on the SP-2000?
The SP-2000 uses a thin-film capacitance relative humidity sensor. The sensor is based on a thermoset capacitive polymer and, using a three-layer capacitance construction, consists of parallel plates with porous platinum electrodes, all mounted on a silicon substrate. The electrodes are coated with a dielectric polymer that absorbs, or desorbs, water vapor from the environment with changes in humidity. The resulting change in dielectric constant causes a variance in capacitance and impedance that relates to changes in relative humidity. In operation, water vapor in the active capacitor’s dielectric layer equilibrates with the surrounding gas. The porous platinum layer shields the dielectric response from external influences while the protective polymer over-layer provides mechanical protection for the platinum layer from contaminants such as dirt, dust and oils. A heavy accumulation of dirt or contamination on the sensor will not affect sensor operation except to slow down the sensor’s
