Patent ID: 8340938

Claim:
A system for evaluating safety critical sensor variables, the system comprising: a computer; a comparator independent of the computer; a first sensor that outputs a first sensor variable e 1 to the computer; and a second sensor that outputs a second sensor variable e 2 directly to the comparator such that the second sensor variable e 2 bypasses the computer; wherein the computer calculates an output variable A based on the first sensor variable e 1 and a first function f 1 according to the equation A=f 1 (e 1 ); wherein the computer calculates a reference variable v based on the output variable A and a second function f 2 according to the equation v=f 2 (A) and the computer outputs the reference variable v to the comparator; wherein the first and second sensor variables e 1 , e 2 are in a relationship involving a third function g according to the equation e 2 =g(e 1 ), wherein the third function g is not the identity function; wherein the second function f 2 is given by a concatenation of the third function g with the inverted first function f 1 according to the equation f 2 =g∘ f 1 ; wherein the comparator compares the reference variable v with the second sensor variable e 2 to determine whether the equation v=e 2 is correct, wherein the comparator determining the equation v=e 2 to be correct is indicative of the computer properly calculating the reference variable v based on the output variable A and the second function f 2 according to the equation v=f 2 (A).