Patent ID: 7426848

Claim:
A method for estimating the composition of a gas, the method comprising: providing a first array of spaced apart carbon nanotubes (“CNTs”) in a closed chamber, at least one CNT in the first array being attached at a first CNT end to a first variable voltage source and having a relatively sharp CNT tip at a second end of the at least one CNT, where the second end of the at least one CNT in the first array is located at a distance in a range of about 10–200 μm from a substantially constant voltage plate; providing a gas, having at least one unknown gas component and having a pressure in a range of about 10 −3 −760 Torr, in the chamber; applying first voltage pulses, having voltages, V(t n1 ; 1)≠V 0 , at a sequence of times t=t n1 (n 1 =1, . . . , N 1 ; N 1 ≧3) to the at least one CNT in the first array, and measuring at least one of a first associated electrical current I(t n1 ;1) and a first cumulative electrical charge e(t n1 ;1) that passes between the at least one CNT in the first array and the substantially constant voltage plate, for each of the N 1 voltages V(t 1 ; 1), V(t 2 ; 1), . . . , V(t N1 ; 1); and estimating a first measured pulse discharge breakdown threshold voltage V(meas;thr) from a comparison of at least one of (i) three electrical current values I(t n1−m1 ;1), I(t n1 ;1) and I(t n1+m2 ;1) with each other; and (ii) three cumulative electrical charge values e(t n1−m1 ;1), e(t n1 ;1) and e(t n1+m2 ; 1) with each other, for selected numbers m 1 ≧1 and m 2 ≧1; providing a threshold discharge voltage value V(k; thr) for each of K candidate gas components, numbered k=1, . . . , K (K≧1); computing an error ε(k) (k=1, . . . , K) that depends upon a difference between the measured breakdown threshold voltage V(meas; thr) and the threshold discharge voltage value V(k; thr); when the error ε(k), for k=k 1 , satisfies at least one of the conditions (1) ε(k 1 )≦e(k 1 ;thr) , where ε(k 1 ;thr) is a selected threshold error, and (2) e(k 1 ;thr)≦min 1≦k≦K ε(k), interpreting this satisfaction as indicating that the gas component no. k=k 1 is likely to be present in the gas G; and when no candidate gas component no. k=k 1 , exists that satisfies at least one of the conditions (1) ε(k 1 )≦ε(k 1 ; thr) and (2) e(k 1 )≦min 1≦k≦K ε(k), interpreting this satisfaction as indicating that none of the gas components no. k=1, . . . , K is likely to be present in the gas G.