| abstract |
A pyroelectric substrate is provided with a heater and at least one set of electrodes for sensing charge redistributions due to changes in the substrate temperature. In a preferred embodiment, there are two interdigitated electrodes, one coated with an absorber/desorber material. The heater pulsatingly raises the temperature of the substrate past the desorption temperature of a fluid of interest. If the fluid was exposed to the absorber/desorber material prior to heating, a portion of the fluid will have been absorbed. When the substrate reaches the desorption temperature, additional heat pulses will not increase the substrate temperature significantly until the fluid has desorbed. Thus, heat used in changing state does not raise the substrate temperature and, lacking a temperature change, reduces the charge redistribution sensed by the electrode coated with the material. Its output is compared with the uncoated electrode (whose temperature continues to rise) and the difference is equal to the amount of fluid desorbed and the temperature is indicative of the species of fluid desorbed. |