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Fantastic DeForest Flame Detector. Invented in 1903 and patented in 1910. Measures approx 11 inches tall with a 3 inch base. A little history on this rare find:
DeForest applied for a patent in 1905, and was issuedU.S. Patent 979275for the flame detector in 1910.
DeForest wrote about the flame audion himself a number of times. For example, see his articles in Western Electrician, November 3, 1906;theFebruary, 1916, edition of Popular Mechanics;the January, 1947, issue of Radio-Craft.
He wrote a more complete scientific paper which was published in the Transactions of the American Institute of Electrical Engineersin 1906.
DeForest is occasionally criticized for not really understanding what was going on inside the triode. This criticism isn’t really fair. It was later discoverd that the Audion acted as an amplifier. It was quite imperfect as an amplifying tube, because it did not have a complete vacuum. But from reading DeForest’s writings, it is clear that he never intended to invent an amplifying tube. He was working on a detector, and the ionized gas within the tube (which wouldn’t have been there if it had been a true vacuum tube) was responsible for this capability. The amplifying ability was, indeed, a lucky accidental discovery. But particularly looking over the 1906 paper, it’s clear that DeForest was an extremely gifted engineer, and he is worthy of the credit he has received for his advancement of radio in the early years.
It seems to me that students looking for an interesting science fair project might be inspired by DeForest’s work. It combines both fire and electricity. Since it had no reasonable commercial use in the early 1900’s, there was no good reason for scientists to pursue it. But it seems to me that interesting things might be going on inside that flame.
DeForest used platinum wire, which is rather expensive. On the other hand, the cost isn’t entirely out of line. For about $20, you can buy enoughPlatinum Wireto construct the detector. Platinum foil would be prohibitively expensive, but there doesn’t seem to be any reason why the salt needs to be contained by the platinum. It seems to me that two platinum wire electrodes could be used. And while DeForest used platinum, there doesn’t seem to be any evidence that he experimented with other metals. Would copper perform the same function?
The flame audion was used as a radio detector by DeForest. But earlier scientists had shown that the flame would conduct electricity, a fact that is obvious from the flow of current through the gap. What flames provide better conductivity? Salt is added presumably because it ionizes better than just the fuel and air alone. It would be a relatively simple matter to measure the conductivity of different ionized materials. Variations in the flame can be heard in the headphones, so for the purpose of making a sensitive radio detector, it’s probably necessary to have a very constant flame. But for many applications, it seems to me that an ordinary candle would suffice.
Being sold as is as found. Please pay upon sale end via PayPal.