Microwave low moisture measuring apparatus

Claim 2

Apparatus for measuring the moisture content of a web including in combination, an elongated strip of dielectric material, means including a conductive support for positioning said strip in contact with the surface of said web, source of a microwave signal, means for applying said signal to said strip as an input thereto adjacent to one end thereof to cause said signal to be propagated along the length of said strip in contact with said surface, and means for deriving an output signal from said strip at a location therealong spaced from said one end and after interaction of said propagated signal with the moisture in said web to afford a measure of the moisture content of the web.

Claim 3

Apparatus as in claim 1 in which said web is disposed along the direction of propagation of said signal in said waveguide.

Claim 4

Apparatus as in claim 1 in which said microwave signal is propagated in said strip in an HE mode.

Claim 5

Apparatus as in claim 1 in which said elongated strip of dielectric material is embedded in said conductive support.

Claim 6

Apparatus as in claim 1 in which said elongated dielectric strip has a central web contacting portion and terminal transition portions, and means for maintaining said transition portions out of engagement with said web.

Claim 7

Apparatus as in claim 5 in which said coupling means and said detecting means comprise respective rectangular waveguides for receiving the ends of said transition portions.

Claim 8

Apparatus as in claim 1 in which said support of conductive material has a slot therein and said strip of dielectric material is in said slot, said slot being formed with respective openings in the base thereof adjacent the ends thereof, said coupling means comprising a first waveguide leading into one of said openings, said detecting means comprising a second waveguide leading into the other opening.

Claim 9

Apparatus for measuring the moisture content of a web including in combination, an elongated strip of dielectric material, means including a conductive support for positioning said strip in contact with the surface of said web, a source of a microwave signal, means for applying said signal to said strip as an input thereto adjacent to one end thereof to cause said signal to be propagated along the length of said strip in contact with said surface, means for producing a reference signal affording a measure of the power level of said source, means for deriving an output signal from said strip at a location therealong spaced from said one end and after interaction of said propagated signal with the moisture in said web, and means responsive to said output and to said reference signal for producing a measure of the moisture content of said web.

Claim 10

Apparatus for measuring the moisture content of a web including in combination, an elongated strip of dielectric material, means including a conductive support for positioning said strip in contact with the surface of said web, a source of a microwave signal, means for applying said signal to said strip as an input thereto adjacent to one end thereof to cause said signal to be propagated along the length of said strip in contact with said surface, means for producing a reference signal affording a measure of the power level of said source, means for deriving an output signal from said strip at a location therealong spaced from said one end and after interaction of said propagated signal with the moisture in said web, and means responsive to said output and to said reference signal for producing a measure of the moisture content of said web.

Claim 11

Apparatus as in claim 8 in which said source of microwave signal comprises means for switching said signal on and off at a rate less than about 100 Hz.

Claim 12

Apparatus as in claim 8 in which said output signal deriving means comprises a thermistor, and a waveguide mount for said thermistor, said apparatus including means for maintaining the temperature of said thermistor substantially constant.

Claim 13

Apparatus as in claim 10 in which said reference signal comprises burst of an alternating current signal of a frequency appreciably less than that of said microwave signal, said apparatus including means for alternately applying said bursts and said microwave signal to said thermistor.

Claim 14

Apparatus as in claim 8 in which said means responsive to said output signal and to said reference signal comprises means for producing a control signal the phase of which relative to the reference signal indicates the relative magnitude of the microwave and reference signals.