![]() ![]() ![]() The “difference” frequencies retain the basic “sound pattern” of the original, inaudible, ultrasonic signals. ![]() “difference” frequencies virtually untouched. Capacitor C10 partially filters the “sum” frequencies from the output of Q3, but it leaves the 0 – 5 kc. These signals combine in the mixer to generate “difference” frequencies between 0 and 5 kc. ![]() signal which is coupled to the base of mixer Q3 along with the 37.5 – 42.5 kc. amplifiers of our hypothetical superhet receiver, amplify the 37.5 – 42.5 kc. Transistors Q1 and Q2, equivalent to the r.f. All sounds that the transducer picks up within this range are passed along to transistor Q1. tuning coil and capacitor, resonates between about 37.5 and 42.5 kc. The circuit, analogous to a radio set’s r.f. When the transducer is plugged into jack J1, it forms a tuned circuit with coil L1. Any odd replacement parts may make wiring unit difficult. Only those parts specified in the Parts List or exact replacements with the same physical size should be mounted on the printed -circuit board. Taking the place of the antenna is an ultrasonic transducer, or “microphone,” of the type used in TV remote-control systems. The Ultrasonic Sniffer is similar in design to an ordinary superheterodyne receiver. Similar surprises await you, so why take a back seat to Rover? Get out your soldering gun and start that flux flowing now! About the Circuit Appropriately (if startlingly) enough, we heard a periodic booming which sounded very much like Big Ben’s chimes. To test the Ultrasonic Sniffer, one of the first things we did after receiving the prototype model was to point it at a Bulova “Accutron” electronic watch. range and “translates” them into frequencies low enough to be perfectly audible. Its ingenious transistorized circuit picks up sounds in the 38 – 42 kc. If the idea intrigues you, you’ll want to build the “Ultrasonic Sniffer” described on these pages. Tune in on the “ultrasonic” frequencies between 38,000 and 42,000 cycles, for example, and a burning cigarette sounds like a forest fire the “secret” noises of animals and insects are clearly audible and a tiny leak in your car’s exhaust system becomes a steam whistle. But even though you can’t normally hear these sounds, don’t assume that they aren’t worth listening to. *** Here’s an old circuit with a new twist-basically a superheterodyne, it brings the not-so-audible world above 16,000 cycles to human ears.ĪRE YOU AWARE that a dog can hear sounds which, if you relied on your ears alone, you probably wouldn’t even know existed? This is because human ears-unlike dogs’ ears-aren’t sensitive to sounds much above 16,000 cycles. The best idea will be rewarded with a $1,000 shopping spree at Adafruit! Note that we’ve retained the old conventions used in the original, e.g., kc versus MHz, μμf versus pf, r.f. Bad steam traps are surprisingly common, roughly 30% of the traps in a plant with no trap testing programs will be leaking! Use an AccuTrak ® Ultrasonic Leak Detector to quickly hear internal flow through steam traps and valves.About this March, 1963 feature, Popular Electronics asks, “How would you build this circuit today?” Share your ideas with us. Leaking steam traps are tremendously inefficient, it's like trying to heat your house with the windows open. If done regularly, this simple test can save tens of thousands of dollars in energy costs. Testing steam traps using ultrasound requires very little training, however a basic understanding of how a particular steam trap operates is certainly helpful. Is the steam trap blowing steam? Listening for the tell-tale rushing sound of a leak enables the user to make an accurate judgement immediately. Utilizing the touch probe on an AccuTrak ® Ultrasonic Leak Detector, you can easily determine if a steam trap is cycling correctly or if it is letting steam blow by. Since the system is closed, it is not possible to know if the steam trap is operating correctly without the proper tools. Steam traps can fail for a variety of reasons causing steam to escape. A major source of energy loss is through leaking steam traps and valves. ![]()
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