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HEWLETT-PACKARD
JOURNAL
T E C H N I C A L I N F O R M A T I O N F R O M T H E - d p - L A B O R A T O R I E S
Vol. 12, No. 1
UBLISHED BY THE HEWLETT-PACKARD COMPANY, 1501 PAGE MILL ROAD, PALO ALTO, CALIFORNIA SEPTEMBER, 1960
A New RF Millivoltmeter
for Convenient Measurements to 1 Kmc
' I 1 HE greatly increasing use of transistors and, A special convenience in an rf voltmeter of this
JL more recently, the introduction of the tunnel wide range is the linear meter scale which minimizes
diode, have placed increased emphasis on low-level reading errors and gives maximum resolution. In
rf voltage measurement. In many applications, a con addition, a temperature compensated detector probe
venient broadband laboratory and production tool is results in low calibration drift, even on the most
needed to replace cumbersome tuned receiver equip sensitive range, so that accurate measurements in the
ment. Measurement of the alpha cut-off of a transis millivolt range can be made with confidence.
tor, the gain-bandwidth of a vacuum tube and the To enable the instrument to drive a dc strip-chart
characteristics of a transmission line or filter network or X-Y recorder, a recorder output jack is provided
are a few examples. at the rear of the cabinet. This output allows auto
To meet this need, the new -hp- Model 411 A RF matic plotting of frequency characteristics that
Millivoltmeter shown in Figure 1 has been devel would normally require laborious point-by-point
oped. This high-sensitivity instrument provides ac measurement. Fig. 2, for example, shows a plot made
curate voltage measurements from 500 kc up to 1 kmc with this output of the frequency response of a 30-mc
and gives useful voltage indications to as high as 3i i-f amplifier at various gain settings. The voltmeter
kmc. This bandwidth, coupled with full scale sensi output is a current proportional to the meter deflec
tivities from 10 millivolts to 10 volts, gives the engi tion and is designed to operate into a 1000-ohm gal
neer working with high frequencies a powerful tool vanometer. Galvanometers of other impedances from
for investigating circuit operation. 0 to 5000 ohms can also be used, a calibrating control
Fig. 1. New -hp- Model 411 A RF Millivoltmeter
makes sensitive voltage measurements to 1 kilomega- Fig. 2. Permanent records of frequency characteris
cycle with -hp- coax tee (foreground) and gives useful tics can readily be made using recorder jack provided
voltage indications to above ) kilomegacycles. If de on new 411 A vtvm. Above recording shows curves
sired, sweep-frequency voltage measurements can be
recorded, as in Fig. 2, using dc output provided made using 411 A to measure frequency response of i-f
by 411 A. amplifier at various gain settings.
P R I N T E D I N U . S . A . C O P Y R I G H T I 9 6 0 H E W L E T T - P A C K A R D C O .