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HEWLETT- PAC K ARD


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 - h p - L A B O R A T O R I E S
Vol.10 No. 11-12

UBLISHED BY THE HEWLETT-PACKARD COMPANY, 275 PAGE MILL ROAD, PALO ALTO, CALIFORNIA JULY- AUGUST, 1959



A Precision DC Vacuum -Tube Voltmeter
with Extended Sensitivity and High Stability
The increasing use of transistors and other 1 millivolt full scale to 1,000 volts full scale
low- voltage devices has made the need for at an accuracy of ±1%. It also measures posi
accurately determining low-level dc voltages tive or negative dc currents from 1 microam
and currents a common problem. To meet this pere full scale to 1 ampere full scale with a
need and to provide for increased accuracy in voltage drop on the sensitive ranges of only 1
making dc measurements in general, the new millivolt maximum. This range of voltage and
dc vacuum-tube voltmeter shown below has current sensitivities thus substantially simpli
been designed. Basically, this instrument is fies the matter of obtaining accurate informa
characterized by a sensitivity 40 to 60 db higher tion in nearly any application involving tran
than that usually associated with such instru sistors and in most applications involving vac
ments, while its accuracy is such as to place it uum tubes.
well within the precision category. At the same The general usability of the instrument is
time the design has achieved very high stabil enhanced by a number of additional conven
ity to enable it to monitor low-level values on iences. The instrument will directly measure
a long-term basis and has avoided such com resistances over a range from 1 ohm center-
mon inconveniences as a grounded terminal scale to 100 megohms center-scale. Output ter
and extended warm-up drift. minals are provided to enable it to be used as
Voltage-wise, the instrument measures posi a very stable dc amplifier and for driving a dc
tive or negative dc voltages over a range from recorder for recording any of the three quanti-




ONE MINOR
TURN -ON DIVISION OF
0-1 SCALE