The ET1 is an electrometer valve. The electrometer is an electrostatic instrument. The electrometer valve is a triode with the highest possible input impedance and was designed to have extremely stable characteristics over time and to be isolated from outside influences. The electrometer valves were operated at very low anode voltages, chosen to be well below the ionisation of any residual gas. Additionally they would be operated in the dark to further remove the valve from any source of unwanted electron emission. These extreme precautions enabled the ET1 to be used to measure currents as low as 10 (to the power) -16 amps. Pin 2 connects to gard rings as well as the screen.
Such valves were used in test equipment such as pH meters.
Note the screw anode connection and the glass rod supports within the valve.
The wide glass tube envelope is 36 mm in diameter and, excluding the B4 base pins, is 184 mm tall.
Reference: 1043. Type ET1 was first introduced in 1939.
Absolute Maximum Operating Conditions¶
Updated January 22, 2013. shape:wide.glass.tube construction:pinch type:triode age:1930.1940 base:b4 pins:4 pin:1.a pin:2.s pin:3.f pin:4.f pin:tc.g1