Abstract: Apparatus and method for measuring the moisture content of a material, particularly a tobacco material, in which a microwave signal is divided between first and second signal paths, said first path comprising a sampling capacitor, the dielectric of which comprises the said material, and said second path comprising reference delay means, signals from each of the paths being fed to a phase detector providing an output indicative of waveform time displacement of one of said signals relative to the other of said signals. Advantageously signals from each of the said paths are fed through substantially identical first and second limiting amplifiers directly to the said phase detector. A second microwave signal of a frequency different from, but close to, that of the first-named microwave signal may be mixed with the signals from the sampling capacitor and from the reference delay means, the resultant beat signals of lower frequency being fed to the phase detector.

Abstract: The invention comprises a method and apparatus for the detection, or detection and concentration determination, of nitric oxide in a gas mixture, particularly in tobacco smoke. The apparatus comprises sampling means operable to isolate a predetermined amount of the gas mixture and pass it to a reaction chamber, means for supplying to that chamber a further gas chemiluminescently reactable with the nitric oxide, and detection means responsive to luminescence emitted in the said chamber. The method comprises operating sampling means to isolate a predetermined amount of the gas mixture and supply it to a reaction chamber, supplying to that chamber a further gas chemiluminescently reactable with the nitric oxide, and operating means to detect luminescence in the said chamber. A carrier gas may be used for transferring the predetermined amount of gas mixture from the sampling means to the reaction chamber.