Two simple, inexpensive systems use electrical resistance measurements to provide useful, immediate information to assist decisions made on irrigation water application. In one system a microprocessor‐based circuit coupled to a programmable calculator provides an on‐site estimate of the time until the next irrigation will be required, based on field data and an operator‐supplied parameter. The second system simply signals the arrival of the wetting front at any location in the soil by giving a visual indication, such as raising a mechanical flag. The microprocessor‐based circuit measures and stores the resistance of four gypsum blocks once a day. The program in the portable calculator accesses this information and uses it to extrapolate the soil drying rate to predict the number of days until the next irrigation. By restricting the microprocessor circuit to data acquisition only and putting all number‐handling routines into the calculator program, the cost and complexity of the microprocessor circuit is minimized, whereas maximizing the programming flexibility. This makes it feasible to install a number of these devices at different locations, all serviced by the same portable calculator.The water infiltration circuit intermittently scans eight sets of stainless steel electrodes to locate the soil wetting front during irrigation. When the resistance across the electrodes decreases, signaling the arrival of the front, the circuit trips a spring‐loaded flag. This provides a visible sign that the wetting front has reached that point in the soil. The equipment worked well. When irrigation was required in six or fewer days, the microprocessor/calculator system made correct predictions 85% of the time. An example of how easily any irrigation scheduling method may be converted to the microprocessor/calculator system is presented.
A water sensor feedback control system was developed to control semiautomatic irrigation of basins and borders. When water reaches a sensor at a downfield irrigation cutoff point, a signal to terminate irrigation is sent via wire or infrared (IR) telemetry to a station controller or receiver at the upper end of the field. The sensor uses a monostable interface to strengthen the signal for wire transmission, and prevents continuous IR transmission during the time the sensor is immersed or remains wet. The water sensor controller, powered by a 12-V battery, uses a silicon controlled rectifier (SCR) triggered by the feedback signal to discharge a capacitor through an electric solenoid. The energized solenoid actuates a gate release or valve to terminate irrigation of one field segment and begin irrigation of another. The water sensor system was tested in a level basin irrigation system.
Small scale yield studies, germination tests, controlled plantings, and packaging often require the counting of large numbers of seeds. The system described in this paper uses a photosensitive detector and a vacuum pickup to count individual seeds and gives a direct digital readout. The count rate is limited only by how quickly the seeds can be fed through the counting tube without clogging it or having them touch each other. This greatly speeds seed counting, eliminates operator error, and reduces operator fatigue. With the addition of a relatively simple predetermining circuit, a fixed number of seeds may be counted and a control function can be exercised. This capability is immediately applicable to packaging or repetitious batching of seeds. Zero error for any given number of seeds is attainable if the seeds are fed through the count tube carefully because of the completely digital nature of the circuit.
e Many studies require that the magnitude of 2 variables be determined simultaneously. Usually this is done by an operator using 2 hand-operated mechanical reciprocating counters. The operator records one variable on one counter and the second on the other. Our sp ecific problem was to determine pollinator densities in field plots. The operators counted a fixed number of flowers and recorded the number of pollinators on these flowers.A number of problems arise from the use of these devices. The reciprocating counters are hard to use, resulting in manual fatigue, and are infamous for missing counts, particularly when they become worn. The operator must have both hands full all the time he is making the count. If the operator must do something else with his hands, he must store the counters where they will not become lost or interchanged.The 2-channel counting system described here overcomes these difficulties by using 2 electromechanical counters mounted in the same case. Pushbutton switches which have a low operating force (1.4 kg nominal) activate these counters. The battery, rather than the operator's thumb, supplies the power to drive the counters. The positive action of the switches and the sound of the counters operating decrease the chance of missed counts. The fixed physical relationship of the counters and unambiguous labeling prevent the counts of pollinators and plants from being interchanged. The simple arrangement of the counter system and decreased operating force speed counting and allow more data to be collected than with mechanical counters. Each counter has a mechanical reset button to clear the counter after a count is completed. Both counters, all the control switches, and the battery are installed in a 13 X15 X 10-cm aluminum box (Fig. 1). The assembled weight of the unit, including the battery, is 1.3 kg. The 10-cm depth of the box is small enough that the operator can grasp the box with the fingers on the underside and the thumbs against the pushbutton switches. This allows the operator to press the pushbuttons positively with little muscular motion, reducing fatigue.By adding a wide strap to suspend the counter unit around the operator's neck, it is possible to free both hands for other tasks as may be required. This arrangement positions the counter where it is always immediately at hand so no time is lost setting up for another count.The electrical schematic, Fig. 2 of these counters is extremely simple and can be assembled by anyone familiar with good soldering technique. The power toggle switch protects the battery in case the counter has something pressed against one of the sensitive count switches in transit or storage which would drain the battery.The parts cost per unit for these electrical counters is ca. $60.00. Although this cannot compete in cost with 2 of the mechanical reciprocating counters which cost in the range of $6.00 to $8.00 each, decreased operator fatigue, elimination of the inherent ambiguity of 2 separate mechanical counters, and increased accuracy because of the ...
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