Patent ID: 7529633

Claim:
A method for estimating a component of a gas, the method comprising: (1) providing a first array of spaced apart carbon nanotubes (CNTs) in a 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 CNT end of the at least one CNT, where the second CNT end of the at least one CNT in the first array is spaced apart a distance d, in a range of about 10-200 μm, from a substantially constant voltage plate; (2) providing a gas G, having at least one unknown gas component and having a pressure in a range of about 10 −3 −760 Torr, in the chamber; (3) identifying K candidate gas components, numbered k=1, . . . , K (K≧1) one or more of which may be present in the gas G; (4) providing a collection of pairs of estimated or known discharge voltage values and corresponding discharge holdoff times {V j (k),Δt(V j (k);ho)} j (j=0, 1, . . . , I k , or j=∞), for the candidate gas component number k, where V ∞ (k) is an estimated or known threshold discharge voltage value, V 0 (k) is an estimated or known prompt discharge voltage value, and V j (k) (i=1, . . . , I k ) is an estimated or known intermediate discharge voltage value (V ∞ (k)<V i (k)<V 0 (k)), and ho refers to a discharge holdoff time value; (5) providing measured values of a threshold discharge voltage value V ∞ (meas), a prompt discharge voltage value V 0 (meas) and intermediate discharge voltage values V i (meas) (i=1, . . . , I k ), corresponding to the estimated or known threshold discharge voltage value, the estimated or known prompt discharge voltage value and the estimated or known intermediate discharge voltage values, respectively, for at least one candidate gas component, number k, of the gas G; (6) computing an error sum ε 1 (k) of weighted magnitudes of differences between (i-a) the estimated or known threshold discharge voltage value, (ii-a) the estimated or known prompt discharge voltage value and (iii-a) the estimated or known intermediate discharge voltage values, and the corresponding (i-b) measured threshold discharge voltage value, (ii-b) the measured prompt discharge voltage value and (iii-b) the measured intermediate discharge voltage values, respectively, for the at least one candidate gas component, number k; (7) when ε 1 (k) is no greater than a selected error threshold number ε 1 (k;thr) for at least one index number, k=k 1 , interpreting this condition as indicating that the candidate gas component number k=k 1 is likely to be present in the gas G; and (8) when ε 1 (k) is greater than the selected error threshold number for all indices k, interpreting this condition as indicating that none of the candidate gas components is likely to be present in the gas G.