Portable filter evaluation apparatus

Claim 2

Apparatus for measuring the level of particle content in a sample of air to determine the efficiency of an air filter located in an air flow system from which the sample is taken, comprising, means for scattering particles contained within air samples being passed therethrough, probe means insertable into areas from which samples of air are to be drawn, means for drawing samples of air through said probe means and said scattering means, a light source positioned adjacent said scattering means to direct light rays onto air-sample particles being scattered in said scattering means, light-responsive signal-generating means positioned adjacent said scattering means and being responsive to the light reflected from said air-sample particles being scattered in said scattering means to develop a signal the level of which is indicative of the particle content in said air sample, means for indicating the level of particle content in said air sample, circuit means responsive to the signal developed by the light-responsive means for controlling the indicating means to indicate the particle-content level, and means for adjusting the circuit means to compensate for any incidental light sensed by the light-responsive means and emanating from a source other than the reflected particles and for any stray electronic signal which would cause and erroneous on the indicating means.

Claim 3

The apparatus of claim 1 wherein the circuit means includes a tube having at least one grid, said tube being biased to control the indicator means in response to the signal generated by the light-responsive means, and the adjusting means includes a presettable regulated potential source which is adjusted when essentially particle-free air is being drawn through the scattering means to set the indicating means to a zero reading even though incidental light and stray electronic signals may be sensed by the light-responsive means.

Claim 4

The apparatus of claim 1 and additionally means for initially adjusting the sensitivity of the light-responsive means to control the indicating means to read an upper limit when the air sample has essentially maximum particle content, and another light source presettable at an intensity comparable to the initially adjusted sensitivity of the light-responsive means for providing an internal standardized light-intensity reference for subsequent calibration of the light-responsive means to a condition simulating an air sample having essentially maximum particle content.

Claim 5

The apparatus of claim 1 wherein said circuit means includes means for selectively operating the apparatus at any one of a plurality of sensitivity levels, and said apparatus additionally comprising means for controlling the light source in response to selective operation of said apparatus at least at the lowest of said sensitivity levels to reduce the intensity of the light from the light source.

Claim 6

The apparatus of claim 4 wherein said light-source controlling means includes an adjustable power source connectable to said light source automatically when said operating means is selectively set to operate the apparatus at least at the lowest sensitivity level.

Claim 7

The apparatus of claim 3 wherein said circuit means includes means for selectively operating the apparatus at any one of a plurality of sensitivity levels, and said apparatus additionally comprising means for controlling the light source in response to selective operation of said apparatus at least at the lowest of said sensitivity levels to reduce the intensity of the light from the light source.

Claim 8

Apparatus for measuring the level of particle content in a sample of air to determine the efficiency of an air filter located in an air flow system from which the sample is taken, comprising, means for scattering particles contained within air samples being passed therethrough, probe means insertable into areas from which samples of air are to be drawn, means for drawing samples of air through said probe means and said scatterg means, a light source positioned adjacent said scattering means to direct light rays onto air-sample particles being scattered in said scattering means, light-responsive signal-generating means positioned adjacent said scattering means and being responsive to the light reflected from said air-sample particles being scattered in said scattering means to develop a signal the level of which is indicative of the particle content in said air sample, means for indicating the level of particle content in said air sample, circuit means responsive to the signal developed by the light-responsive means for controlling the indicating means to indicate the particle-content level, means for initially adjusting the sensitivity of the light-responsive means to control the indicating means to read an upper limit when the air sample has essentially maximum particle content, and another light source presettable at an intensity comparable to the initially adjusted sensitivity of the light-responsive means for providing an internal standarized light-intensity reference for subsequent calibration of the light-responsive means to a condition simulating an air sample having essentially maximum particle content.

Claim 9

Apparatus for measuring the level of particle content in a sample of air to determine the efficiency of an air filter located in an air flow system from which the sample is taken, comprising, means for scattering particles contained within air samples being passed therethrough, probe means insertable into areas from which samples of air are to be drawn, means for drawing samples of air through said probe means and said scatterg means, a light source positioned adjacent said scattering means to direct light rays onto air-sample particles being scattered in said scattering means, light-responsive signal-generating means positioned adjacent said scattering means and being responsive to the light reflected from said air-sample particles being scattered in said scattering means to develop a signal the level of which is indicative of the particle content in said air sample, means for indicating the level of particle content in said air sample, circuit means responsive to the signal developed by the light-responsive means for controlling the indicating means to indicate the particle-content level, means for initially adjusting the sensitivity of the light-responsive means to control the indicating means to read an upper limit when the air sample has essentially maximum particle content, and another light source presettable at an intensity comparable to the initially adjusted sensitivity of the light-responsive means for providing an internal standarized light-intensity reference for subsequent calibration of the light-responsive means to a condition simulating an air sample having essentially maximum particle content.

Claim 10

The apparatus of claim 7 wherein said circuit means includes means for selectively operating the apparatus at any one of a plurality of sensitivity levels, and said apparatus additionally comprising means for controlling the light source in response to selective operation of said apparatus at least at the lowest of said sensitivity levels to reduce the intensity of the light from the light source.

Claim 11

Apparatus for measuring the level of particulate content in a sample of air to determine the efficiency of an air filter located in an air flow system from which the sample is taken, comprising, means for scattering particles contained within air samples being passed therethrough, probe means insertable into areas from which samples of air are to be drawn, means for drawing samples of air through said probe means and said scattering means, a light source positioned adjacent said scattering means to direct light rays onto air-sample particles being scattered in said scattering means, light-responsive signal-genErating means positioned adjacent said scattering means and being responsive to the light reflected from said air-sample particles being scattered in said scattering means to develop a signal the level of which is indicative of the particle content in said air sample, means for indicating the level of particle content in said air sample, circuit means responsive to the signal developed by the light-responsive means for controlling the indicating means to indicate the particle-content level, said circuit means including means for selectively operating the apparatus at any one of a plurality of sensitivity levels, and means for controlling the light source in response to selective operation of said apparatus at least at the lowest of said sensitivity levels to reduce the intensity of the light from the light source.

Claim 12

Apparatus for measuring the level of particulate content in a sample of air to determine the efficiency of an air filter located in an air flow system from which the sample is taken, comprising, means for scattering particles contained within air samples being passed therethrough, probe means insertable into areas from which samples of air are to be drawn, means for drawing samples of air through said probe means and said scattering means, a light source positioned adjacent said scattering means to direct light rays onto air-sample particles being scattered in said scattering means, light-responsive signal-genErating means positioned adjacent said scattering means and being responsive to the light reflected from said air-sample particles being scattered in said scattering means to develop a signal the level of which is indicative of the particle content in said air sample, means for indicating the level of particle content in said air sample, circuit means responsive to the signal developed by the light-responsive means for controlling the indicating means to indicate the particle-content level, said circuit means including means for selectively operating the apparatus at any one of a plurality of sensitivity levels, and means for controlling the light source in response to selective operation of said apparatus at least at the lowest of said sensitivity levels to reduce the intensity of the light from the light source.

Claim 13

The apparatus of claim 9 wherein said light-source controlling means includes an adjustable power source connectable to said light source automatically when said operating means is selectively set to operate the apparatus at least at the lowest sensitivity level.