A Screen-Grid Voltmeter without External Leak

A highly sensitive screen-grid voltmeter using type 24 (or 32) tubes without grid leak is described. Static and transrectification characteristics of single and twin tubes and of tube circuits including a load resistance are shown. The voltmeter is independent of frequency from low audio to ultra-high frequencies. The useful range of the twin (full wave rectifying) circuit is from 0.05 to 20 volts root-mean-square; this can be extended to higher voltages as desired by suitable choice of blocking condensers. The range from 0.1 to 10 volts has a linear calibration curve. Over this range the transrectification factor ∂It/∂eg= 2.05 × 10^-3. The input admittance of the device is very low. Applications of the circuit for use as a peak voltmeter, as a resonance indicator, as a radio detector, and as a high-frequency intensity meter are briefly discussed.