Patent ID: 8257976

Claim:
A method of optically monitoring multiple parameters of an oil sample, the method comprising the steps of: providing an oil-absorbent sampling substrate; wherein the sampling substrate contains a plurality of first test zones comprising a first optical property that is responsive to a first parameter of the oil, and at least one second test zone comprising a second optical property that is responsive to a second parameter of the oil; contacting the oil with the sampling substrate such that a sample of the oil is brought into contact with at least a portion of each of the first test zones and at least a portion of the at least one second test zone; interrogating the first test zones by a first optical method so as to receive a set of first signals from the first test zones; combining the set of first signals from the first test zones into a combined signal; correlating the combined signal with the first parameter of the oil; interrogating the at least one second test zone by a second optical method so as to receive a second signal, wherein the second optical method is different from the first optical method; and, correlating the second signal with the second parameter of the oil.