Sensorelement zur gleichzeitigen Messung von zwei verschiedenen Eigenschaften einer chemisch sensitiven Substanz
The sensor (10) consists of a quartz substrate (12) coated with a substance (30) which is chemically sensitive to a component in the fluid. Two arrangements of sensors (12,14a,14b and on line AA') are provided to detect changes in a property, e.g. the mechanical and electrical properties, of the chemically active substance. The electrical property detected may be the dielectric constant or the conductivity. The mechanical property may be the mass, viscosity or shear strength. The first set of sensors (12,14a,14b) consists of metallic electrodes attached to the substrate such that a piezoelectric oscillation is produced in the substrate as a result of electric oscillations applied to the two electrodes (14a,14b). The second set of sensors (on AA') uses an interdigital capacitor whose capacitance or conductivity changes with the chemically active substance, to measure the electrical properties. A heater and temperature sensor may be fitted in addition. ADVANTAGE - Reduces cross-sensitivi ty to other chemicals, e.g. to humidity in gas concentration measurements.
DE 1996-19644290 A: 19961024