Patent ID: 7955560

Claim:
A system for monitoring operational status of sensing devices for determining a concentration of a chemical component in a fluid, the system comprising: a first sensor comprised of a capacitor having a pair of electrical conductors with a gap therebetween for receiving the fluid, said first sensor producing a first electrical signal in response to a first physico-chemical property of the chemical component; a second sensor comprised of piezoelectric material supporting a chemical that interacts with the chemical component in the fluid to sense the mass of the chemical component in the fluid by frequency changes of the piezoelectric material, said second sensor producing a second electrical signal in response to a second physico-chemical property of the chemical component, wherein said first physico-chemical property is different from said second physico-chemical property; and a processing system for receiving the first and second electrical signals, said processing system including: (a) means for determining a first concentration of the chemical component by referencing the first electrical signal to a first set of stored data, (b) means for determining a second concentration of the chemical component by referencing the second electrical signal to a second set of stored data, (c) means for comparing the first concentration to the second concentration to determine whether the first concentration falls within a pre-set percentage of the second concentration, and (d) means for determining that at least one of said first and second sensors is defective if the first concentration falls outside the pre-set percentage of the second concentration.