There are, of course, many reasons why the physical characteristics of a particular volume of air might be of interest. For instance, knowing the temperature, humidity and air flow parameters of a volume of air can be very helpful in determining the effect the air may have on a specific environment. Aside from weather observations, where massive volumes of air must be considered important, there are also many instances when rather small volumes of air need to be analyzed. Specifically, consider air conditioning systems.
Most air conditioning systems rely on the circulation of air through a cycle wherein air from the particular environment to be controlled is passed through equipment that cools the air and returns it to the environment. Whether the particular air conditioning equipment is efficient for accomplishing this task is a matter of some concern. For instance, power efficiency is of interest, as well as is the ability of the equipment to comply with its control inputs.
In the past, in order to determine whether air conditioning equipment was efficient for its intended purposes it was typically necessary to compare the equipment's actual operating characteristics with the operational specifications that are established for the equipment by the manufacturer. Often times, this required invasive measurements of the system coolant. More recently, it has been recognized that the efficiency of an air conditioning system can be noninvasively determined by merely analyzing characteristics of the air that passes through the equipment. For example in U.S. application Ser. No. 08/914,475 which was filed on Aug. 19, 1997 for an invention entitled "DIAGNOSTIC UNIT FOR AN AIR CONDITIONING SYSTEM", and which is assigned to the same assignee as the present invention, noninvasive equipment for diagnosing the efficiency of an air conditioning system has been disclosed.
All systems for diagnosing air conditioning equipment must rely on either measurements of the equipment's operating parameters, measurements of the air that is being conditioned by the equipment, or a combination of the two. When direct measurements of the air are taken, it is necessary to obtain such measurements from a good representative sample of the air. Otherwise, the measurements will be essentially meaningless. For very small volumes of air, this may be a relatively easy matter. Indeed, for very small volumes of air one sensor unit will normally suffice for taking measurements of temperature, humidity and fluid volumetric flow velocities. When larger volumes of air are involved, however, the situation becomes somewhat more complicated.
In order to measure characteristics in the flow of a volume of air through rather large ducts, such as are common for both commercial and residential air conditioning systems, it may be necessary to take several measurements of the air volume. Typically, this is done at several different locations in the fluid air flow. For example, in order to accurately measure the characteristics of air flowing through a five or six square foot orifice of an air duct, ten or twelve samples of the air may need to be taken at as many different locations in the orifice. Otherwise, meaningful and reliable readings for the total flow of air through the orifice may not be obtainable. Not surprisingly, this can be time consuming and tedious.
In light of the above it is an object of the present invention to provide an air sampling system which is able to simultaneously collect diverse samples from a volume of air and combine them into a single sample that is representative of the entire volume of air as it flows through an orifice. Another object of the present invention is to provide an air sampling system which is able to direct a representative sample of air toward a single sensor for an analysis which determines the average characteristics of the entire volume of air from which the sample is taken. It is yet another object of the present invention to provide a method for measuring selected characteristics of a volumetric air flow which are useful for diagnosing air conditioning equipment. Still another object of the present invention is to provide a system for sampling volumetric air flow, together with its concomitant method of operation, which is relatively easy to manufacture, simple to use, and comparatively cost effective.