The Series RF-1OA High Frequency Vacuum Tube Test Probe is
specifically designed for A.C. voltage measurements over a
wide range of frequencies when used in conjunction with
PRECISION Vacuum Tube Voltmeters.
Precision Vacuum Tube Voltmeters are basically D.C. voltage
In order to provide facilities for measuring high frequency
A.C. voltages, a high impedance rectifier probe must be used
in conjunction with the Vacuum Tube Voltmeter. Series RF-10A
is specifically designed to perform this function through
the rectification action of the probe tube circuit. This
rectifier network converts the high frequency A.C. voltage
under test to a proportionate D.C. value and feeds this D.C.
voltage to the V.T.V.M. Circuit.
Analysis and Examination of the RP-10A schematic will reveal
that the circuit is of the peak indicating type. The D.C.
output of the probe which is applied to the D.C. V.T.V.M.
assumes a value substantially equal to the positive peak
voltage of the A.C. applied to the tip of the probe.
Basically this relationship between the
A.C. Input and the D.C. output of the probe is true only
when the rectified probe output feeds into an infinitely
high D.C. load resistance as would be typified by the grid
circuit of a vacuum tube.
The design of Precision Vacuum Tube Voltmeters are such that
an infinitely high input circuit load cannot be obtained, in
that the permanent V.T.V.M. input resistance is 13-1/3
megohms on all D.C. voltage ranges. Accordingly the
rectified output of Series RP-10A is never quite truly equal
to the full peak A.C. input to the tip of the Probe.
However, the difference is small enough to permit
calibration on the basis of true positive peak voltage.