A new method for the detection of thin conducting films in thermionic valves

A method has been devised for the detection of thin conducting films on insulating surfaces, but its application has so far been restricted to the detection of films in thermionic valves, for which it is particularly suitable. Known as the `triple-band method¿, it is simple, does not call for special valve constructions and requires only normal laboratory equipment. While the method was developed as a means of film detection, calculations have been made which show that the technique could be used for quantitative measurements.