Multipurpose analog pulse height computer performs real-time arithmetic operations on relatively fast pulses. This computer can be used for identification of charged particles, pulse shape discrimination, division of signals from position sensitive detectors, and other on-line data reduction techniques

Brenner, R.

Strauss, M. G.

English

NASA Technical Reports Server

December 1967	 Brief 67-10626 
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Icy V
AEC-NASA TECH BRIEF 
YES
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Versatile Analog Pulse Height Computer • 
Performs Real-Time Arithmetic Operations 
X 
O1OVSLG—I 
Input
Log Function Generator	 .	 Antilog Function Generator 
Log	 [	 +vS[IO-l2Omv	 IReference —LOG X Current
O-12OmTE
LOG X
	
ponent X
Antilog 
Reference IRAL. 
Current 
log R4
Summer 
Log Summer Output 
&  
Multiplier vs
	
0-120mv
V0 = lR5(e'_1) 
H 1--1LI0-i ov 
Antilog 
Output Log 
Reference 
Current 
Y	 R 
0-1 Ov TSLO-1 l—W-
Input	 ly
—LOGY R
 
A 01 20J 
lfIO_l2Omv 
LOG Y 
LOGY=2.3	 log!J. 
Log 
Element
Exponent Y
	 - 
Antilog 
Element 
V = ± LOG X ± LOGY 
The problem: 
To design a multipurpose pulse computer capable 
of performing real-time arithmetic operations on rela-
tively fast pulses. Experimental techniques in nuclear 
physics often require arithmetic operations on pulses 
whose amplitudes convey the experimental data. 
These pulses may be digitized and operated on by 
on-line digital computers, if the computers are fast 
enough to handle the event rate and large enough 
to store all the parimeters in question. Otherwise, 
an inexpensive analog computer can be used in con-
junction with a multichannel or multiparameter ana-
lyzer. However, all analog pulse multipliers, dividers,
and other similar circuits tried to date have had inad-
equate dynamic range, drift due to high counting rate, 
or slow response, and each of these circuits was de-
signed to calculate only one specific function. 
The solution: 
A general purpose analog pulse height computer, 
capable of pulse height multiplication, division, ex-
ponentiation, addition, and subtraction. These opera-
tions are performed in about 0.5 asec. with a pre-
cision of ±0.1% of full scale over a pulse height range 
of 20:1. The computer has been used successfully for 
identification of charged particles, pulse shape dis-
crimination, measurement of mass yield distributions 
(continued overleaf) 
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Administration. Neither the United States Government nor any per- method, or process disclosed in this document may not infringe pri-
son acting on behalf of the United States Government assumes any vately owned rights.
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in fission, division of signals from position sensitive 
detectors, and generation of nonlinear energy scales 
in multichannel analyzers as well as for other on-line 
data reduction techniques. 
How it's done: 
Pulse height multiplication, division, and exponen-
tiation can all be performed through the use of loga-
rithms and antilogarithms; addition and subtraction 
are performed by using linear operational amplifiers. 
The log and antilog function generators are based on 
the fact that the logarithm of the collector current 
in a silicon planar transistor is proportional to its 
emitter-base voltage. Logarithmic conversion is ob-
tained by connecting the log transistor as a feedback 
element in an operational amplifier. The output volt-
age of this amplifier is proportional to the logarithm 
of the input current. 
The basic analog computer, shown in the figure, 
consists of two identical log function generators and 
an antilog function generator. The log function gen-
erators generate signals proportional to the logarithm 
of the input. These are coupled out via a noninverting 
and an inverting buffer to produce LOG and -LOG 
signals. In the antilog circuit, LOG X (or -LOG X) 
and LOG Y (or -LOG Y) are amplified, i.e., multi-
plied by a constant equal to R4/R2 and R4/R3, re-
spectively. The resultant signals are summed in the 
operational amplifier and the antilog corresponding 
to the. sum is generated. The constants R4/R2 and 
R4/R3 represent the exponents to which X and Y have 
been raised, and they can be varied between 0.4 and 
2.5 by adjusting the 10-turn potentiometers R2 and 
R3. Multiplication is performed by summing two 
LOG signals, and division by summing a LOG and a 
-LOG signal.
Patent status: 
Inquiries about obtaining rights for commercial 
use of this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U. S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argonne, Illinois 60439
— 
•St1l 3	
Sol IV R11V 
Additional information includes a detailed discus-
sion of the computer circuitry, performance tests, and 
applications. 
Notes: 
1. Performance tests have shown that at room tem-
perature the computer exhibits a drift of about 
0 .05%/Co
 or ±0.03%/day. With an input rate of 
10,000 counts/sec, the pulse height distribution 
shifts 0.2%, and with 25,000 counts/sec, it shifts 
2. This information should be of interest to those 
concerned with the design, development, and use 
of instruments for nuclear pulse spectrometry and 
telemetry instrumentation. 
3. Additional details are contained in Review of Scien-
tific Instruments, vol. 36, no. 12, p. 1857-1876, 
December 1965. 
4. Inquiries concerning this innovation may be di-
rected to:
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 South Cass Avenue 
Argonne, Illinois 60439 
Reference: B67-10626 
Source: M. G. Strauss and R. Brenner 
Electronics Division 
(ARG-10052)	 - 
Brief 67-10626	 Category 06


Versatile analog pulse height computer performs real-time arithmetic operations

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