Dynamic Measurement of Electron Tube Coefficients

Circuits are described for the dynamic measuremtent of amplification factor, electrode resistance, and transconductance; and are shown to be suitable for the measurement of both positive and negative values of all three coefficients over wide ranges. The circuits are analyzed for the general case in which the grid is conductive and the grid current is appreciably affected by variations in plate voltage. It is shown for each circuit that if the impedances of the test voltage sources are sufficiently low, the method employed for balancing capacitance currents introduces no error regardless of the value of the plate resistance. Under the same condition no correction need be applied for the impedance of the measuring apparatus. The analyses are for the grid-to-plate coefficients of a triode but are directly applicable to the measurement of grid-circuit coefficients or of coefficients relative to any pair of electrodes of a multielement tube. A description is given of a measuring instrument in which the three circuits are incorporated.