Iron-hydrogen resistor

An iron -hydrogen resistor is a PTC resistor and consists of a hydrogen-filled glass tube similar to a light bulb, in which a steel wire is located. Iron -hydrogen resistors today have no meaning - they were replaced by constant current sources in the form of electronic circuits.

Function

Iron -hydrogen resistors PTC and constant current sources. If the resistance wire is loaded such that its temperature is about 700 ° C, the temperature dependence of the electric resistance of the iron comes to bear. With increasing voltage, and the associated greater warming, the value of the resistance is increasing by leaps and bounds, making it a dark red glowing area in the wire. With increasing voltage, this area continues to grow at the expense of not glowing portion. The hydrogen filling not only protects the iron from oxidation, but also causes the effect that at 700 ° C, the solubility of hydrogen increases sharply in the iron and thus also the electric resistance.

Application

Iron -hydrogen resistors were developed as series resistors for operation of the Nernst lamp.

They had a somewhat greater importance in the meantime in broadcasting technology. In Allstromgeräten they were connected in series with the filaments of electron tubes and stabilized the current flow in the heating circuit with fluctuating mains voltage. In addition, was a so-called URDOX for inrush current limiting resistor ( thermistor, which was manufactured until 1936 of uranium dioxide ) in the heating circuit. This was partly accommodated with the iron wire in the same flask.

They were also used in Entregungseinrichtungen for synchronous machines and large reactors.