Publisher's Synopsis
Excerpt from Instruments and Methods Used in Radiometry II
In the instruments now to be described, the success attained in construction results from the use of the electrically heated welding device and from the choice of wire (silver) which is easily freed from sulphide. The silver wire contributes but little thermo electrically, but this is compensated by its extremely low resistance, which is about ohms per centimeter for wire 5 mm in diameter. One need not, therefore, exercise any great care in making the silver wires of a minimum length to produce a low resistance thermopile. A preliminary heating brightens and anneals the wire; a procedure which can not be followed in cleaning copper and iron wire. The use of pure tin in welding produces an alloy which is not brittle. The construction of the thermo elements of bismuth and silver is therefore an easy process so that after attaining some skill they can be made at the rate of 15 to 20 per hour. The instrument can, therefore, be built in any laboratory, and of the proper design to suit the problem under investigation.
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