X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
1999-05-04
2003-02-25
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Absorption
C378S051000, C056S01020R
Reexamination Certificate
active
06526120
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to mass flow monitoring of materials, including agricultural materials and food products. More particularly, though not exclusively, the present invention relates to a method and apparatus for using x-ray techniques for monitoring flow rate of materials including biological materials.
Flow rate measurement of agricultural materials and food products is a subject that appears frequently during harvesting, handling and transportation, and in food processing, conveying, and storage stages. While measuring the amount of crop being loaded to/from various transportation vehicles is important for obvious reasons, knowing the amount of material flowing into various physical or chemical processes at food processing plants is vitally important for a proper blend of various elements to go into these processes. In addition to these, in farming, crop flow rate measurement is a subject to growing interest at the harvest stage as well. This forms an important element of a new concept known as precision farming briefly described below.
There is considerable spatial variability in soil properties such as nutrient availability and pH levels within a given field. Factors such as water availability, poor drainage, and variations in topography introduce other dimensions to spatial variabilities resulting in varying yield patterns within a single field. These variabilities traditionally have not been taken into account when practicing soil and crop management. Applying uniform input rates of fertilizers and chemicals may result in excessive agrochemical deposition in some of the areas of a field depending on local requirements. Conventional farm management thus contains two major drawbacks. First, higher application rates than necessary in a certain location would increase the application cost. Second, excessive input application causes surface and groundwater contamination through surface runoff and chemical leaching.
Therefore, it makes more sense to vary application rates of agricultural inputs depending upon the localized needs in a field. This management strategy would help optimize yield obtained from locations having different fertility levels. Thus, as opposed to field-based practices, variable rates of physical and chemical inputs (such as seeds, water, fertilizers and chemicals, and tilling of the soil) should be applied to different areas of a field. In order to achieve this goal, regions of a field with the same yield potential need to be mapped. Creating management zones (small management areas) would help identify the cause-and-effects of the local yield variability. Geographic Information Systems (GIS) can be used to store the spatial soil and yield data, analyze and display results in the form of tables and/or maps, and identify most promising crop and management practices.
The adoption of precision farming includes two major thrusts. One involves the evaluation of outcomes of certain physical and chemical procedures implemented in the field on the basis of databases formed through data acquisition over years. The data acquisition includes yield data in order to generate crop yield maps. Agricultural crop flow measurement is a key parameter in forming yield maps, and accurate measurement of flow rate has a lasting impact on forming reliable databases to be used in precision farming. The second thrust involves development of new machinery, equipment, and sensors to be used in precision farming practices. Specifically, the development of more advanced sensors for data acquisition is very important and will have a lasting impact on overall precision farming activities.
To practice site-specific farming (also known as prescription farming, precision farming, site-specific management, spatially variable farm management, and variable rate technology (VRT)), the position of farm equipment must be determined accurately in real-time while working in the field. By knowing the precise location of the farm equipment, inputs can be applied using predetermined application rates. Amongst various position determination methods, Differential Global Positioning System (DGPS) is the most effective means of 3-D positioning. The location data can be tagged with spatial data to generate maps of applications rates, yield, moisture, pH, and other variables of interest.
The cause-and-effects of yield need to be determined to be able to optimize yield spatially and to reduce environmental contamination due to chemical applications. This requires accurate mass flow rate measurement for materials being harvested since yield maps provide understanding about crop response to various crop management practices in a specified management zone.
METHODS OF FLOW RATE MEASUREMENTS
Many methods have been used in an attempt to measure flow rates of agricultural products. Two types of yield monitors have been used in the prior art: mass flow meters and volumetric flow meters. Mass flow meters determine the mass of flowing material continuously. Volumetric flow meters are used to measure the volume of product on-the-go as well. The measured volume is converted into standard mass by the manipulation of appropriate conversions.
Commercial volume-based sensors include a paddle-wheel sensor and an infrared sensor (photo-optical sensor). Research prototypes of volumetric sensors include an ultrasonic sensor and Light Emitting Diodes (LED). Commercial mass flow rate sensors available to farmers are impact-based plate sensors (strain-gage based load cells, weigh pads, and potentiometers), a nuclear sensor (gamma ray sensor), and conveyor belts. Examples of research prototypes of mass flow sensors include a change of momentum plate, a pivoted auger, a piezo-film based sensor, and a capacitive sensor. These prior art sensors are described briefly below.
Mass Flow Meters
A nuclear sensor (gamma ray) system consists of a gamma ray emitter, a detector, and a display unit. The material flows through a measuring gap between the emitter and detector. The number of photons registered by the detector is reduced by the material as it flows through the sensing volume. Material flow is calculated by the reduction of the number of photons. One problem with nuclear sensors relates to safety. Nuclear sensors use isotopes that require careful handling and extensive shielding. For example, for a nuclear sensor operating at 660 keV, shielding of approximately ½ inches of lead or 6-7 inches of steel may be required.
An impact-based sensor system may include strain-gage load cells, weigh pads (platform scales), and potentiometer load cells. All of these sensors use the same principle in determining the mass flow rate of agricultural product. These sensors measure the force exerted by the material as the material hits the sensing element, which is related to the flow rate of the material.
A change of momentum sensor includes a curved plate mounted at the exit of the clean gain elevator of a combine. Friction and impact forces change the direction of the material, such as an agricultural product, on the curved plate. The momentum of the agricultural product changes as the direction is forced to change on the flowing material. The difference in the average material speed is maintained constant between the inlet and outlet of the sensor. The mass flow rate is directly proportional to the force measured by a force transducer attached to the curved plate.
A capacitive sensor works on the principle that the dielectric constant of air/material mixture increases with increasing material concentration in a transport tube. The concentration of the material is determined by using capacitor plates around the transport tube. This method is claimed to be non-intrusive and insensitive to transmitted vibration. Calibration depends on the material being measured and varies with material distribution within the sensor.
With pivoted auger sensors, one end of an auger is supported by a load cell and the other end is pivoted. Agricultural product flows off the agricultural product auge
Arslan Selcuk
Gray Joseph N.
Inanc Feyzi
Bruce David V.
Hobden Pamela R.
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