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(IO) “Behaviour of a Balanced D.C. Amplifier” (12) " Electrometer Tubes for the Measurement of Small
by R. C. SPENCER and LEROY SCHULZ. Rev. Sci. Inst., Currents"
Vol. 14, p. 10 (Jan., 1943). by J. A. VICTOREEN. Proc. I.R.E., Vol. 37, No. 4
(April, 1949).
The Barth circuit is here modified in order to: The measurement of currents of the order 10 -12 amp.
(i) Eliminate the effect of control grid potential by thermionic electrometer valves is discussed from a
changes upon the value of the filament current practical viewpoint. Low grid current and high leak-
at which a balance is obtained. age resistance techniques are outlined.
(ii) Move together the two or more values of the fila- (13) “ Electrometer Valve Balanced Circuits, with special
ment current at which a balance exists. reference to the Ferranti B.M.4.A
by H. A. HUGHES. Electronic Engineering, 23, 217
(iii) Increase the range of balance and thereby elimin- (1951).
ate the necessity to “flash” valves (having low Progress in electrometer valve balanced circuit de-
anode current) in order to facilitate balancing. sign is here reviewed. Equations are derived which
describe the behaviour of the Barth and the Caldwell
balanced circuits. Data presented relates to the use of
the Ferranti B.M.4.A indirectly heated electrometer
(1 1) “ A New Balanced Electrometer Circuit ” valve in the Barth, the Caldwell and the DuBridge
by P. A. CALDWELL. Review Scientific Inst., Vol. 19, Brown circuits.
No. 2 (Feb., 1948). (14) “ D.C. Amplifiers. Methods of Measuring Small Direct
Here an electrometer circuit is described in which it Currents and Potentials ”
is possible to choose the resistances such that the by J. YARWOOD and D. H. LE CROISSETTE. Electronic
anode voltage is independent of the supply voltage at Engineering, Pts. (1) to (3), Jan./Mar., 1954.
the electrometer valve operating point. When the circuit The principles of the single-valve amplifier for the
is used as the input stage of a direct-coupled amplifier, amplification and measurement of small unidirectional
this leads to a simplification of the amplifier design. currents and potentials are established. Grid current
The equations determining the circuit constants in and electrical leakage, and methods of measuring and
terms of the electrometer parameters are derived. A reducing them, are derived. Triode and tetrode electro-
first stage differential d.c. amplifier of the type required meter valves in single- and double-valve circuits are
for this-circuit is described by Nier, Ney, and Ingrham, reviewed relative to the current and voltage sensitivities
Rev. Sci. Inst. 18, 294 (1947). attainable.

ACKNOWLEDGMENT-The author is indebted to Messrs. Ferranti Ltd. for permission to publish the above
data-which was compiled during the course of the development and pre-production stages of this valve.

Membership Elections and Transfers

The following recent elections and transfers have been recorded in the Membership Register of the Institution
of Electronics:-
Direct Election to Honorary Member:-
CLARKE, Rear Admiral Sir Philip, K.B.E., C.B., D.S.O. Kenley

Direct Election to Member:-
HICKSON, Kenneth. Wigan. ROBERTS, John. Wigan.
Direct Election to Associate Member:-

ALLENBY, Reginald T. Urmston. HUMPHRISS, Ernest L. Woolton.
ATKINSON, Ivan. Whitehead (N. I .) HUMPHRISS, Raymond L. Woolton.
BAKER, Peter N. She field. JACKLIN, Ivan H. Nottingham.
BAKER, Richard J. Basingstoke. JACKSON, Robert J. West Derby.
William J. T. Basingstoke.
JINMAN,
BARKS, Norman. Derby. JONES, Peter J. Oldham.
BARRY, James H. Hull. KENNY, Ernest. Gosforth.
BASSHAM, Alan. West Hartlepool. LEE, John J. Burhill.
BATES, John R. Bangor (N.I.) LEWIS, Eric H. St. Helens.
BELL, John S. Hull. MACHIN, Geoffrey. St. Annes-on-Sea.
BODEN. Peter. Shaw. MERRICK, William. Standish .
BROCKLEHURST, Ronald. Huyton with Roby. NICHOLS, Geoffrey J . Aintree.
BURY, John E. Swinton. O’HARE, Harold J. Openshaw.
CARTER, Walter G. Stretford. PARKS. Bertram H. Wantage.
CHESTERS, John L. Stoneycroft. PHILIPSON, William. Greasb y.
CUTLER, George D. Mitcham. PLANT, Cecil R. Chesterfield.
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