Application of the Equivalent Circuit in Measuring μ

Author: E.E. Kimberly

Fig, 27-15. Circuit for Measuring μ

The circuit shown in Fig. 27-15 may be used in measuring μ. The impedance Z_e is the impedance of the coupling transformer as measured from terminals T₁ and T₂. The batteries do not appear in the equivalent circuit because only the incremental voltage is to be used and the battery resistances are negligible. The resistance Rp is the equivalent internal plate resistance of the triode. The voltage drop between cathode and grid is V_kg = - IR₁ The voltage rise is

from which

If the values of R₁ and R₂ are so adjusted that I_p does not exist, there will be no signal at T₁ and F₂ and no signal voltage across Z_e. The two loop circuits are then said to be balanced. When I_p = 0, μR₁-R₂ = 0 in Equation (27-17) and