(under subclass 49) Subject matter wherein the incandescent standard is an electrically heated filament and means are provided to control the current through the filament.
(1) Note. These instruments may include optical elements to change the color and intensity of the unknown radiation or the standard radiation.
SEE OR SEARCH THIS CLASS, SUBCLASS:
46, for the electrical circuits, per se, which power the electrical incandescent standard.
231, for photometers which utilize an electrical incandescent lamp which includes means to vary filament current.
SEE OR SEARCH CLASS
315, Electric Lamp and Discharge Devices: Systems, 129+, for electrical circuits supplying current to a lamp, which is not an electrical test standard, which circuit includes an electrical indicator.
374, Thermal Measuring and Testing,
129, for radiation pyrometers which include an electrically variable incandescent standard.
