Osram ET1 electrometer triode
This valve is designed to have a very high input resistance so it can be used anywhere an electrometer is required. The control grid is connected to a terminal at the end of a special high resistance glass stem. The interal and external guard rings and an electrostatic shield are connected to the base, and may be connected to the negative side of the filament or given any desired negative potential. To give the minimum possible electrical leakage the operating grid potential should be greater than 2V negative with respect to the filament, the glass should be perfectly clean and dry, and the valve should be operated in the dark. In extreme cases it is also necessary to screen the valve and input circuit, to use an anti-microphonic mounting, and to ensure the filament supply does not fluctuate.
This file was last modified
23:59:16, Friday March 13, 2015