Consumption multichannel pulse height analyzer performs balloon and rocket investigations of solar neutrons with energies greater than 10 MeV. The lightweight unit can operate in a temperature range of minus 30 degrees to plus 70 degrees C and withstand storage temperatures from minus 50 degrees to plus 90 degrees C

Ewald, C. J.

Sarkady, A. A.

English

NASA Technical Reports Server

I* 1 Linear Gate 
ut pu Signal 
•-°'	 I	'Ci I	 C2 can	 I Gate	 Gate
August 1967	 .	 .	 Brief 67-10258 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Multichannel Pulse Height Analyzer Is Inexpensive, 
Features Low Power Requirements 
I Reset I
Circuit 
Anti-	 I 
coincidence	 I Input	 I
Co I Gate I	
.fger I	
[
C.Scan Control I I Scan I	 Scan 
C3 [__J C4 
Scan	 Scan 
C3
^GCate
 
Gate  
	
PHTC _______ 
2 Mc L_J 2 Mc I	 Ii Mc Gate	 I	 I Scaler1	 1 Scaler 
2 Mc 
Current Oscillater
Scaler'	 Scaler'	 -Scaler Scaler l-..Scaler 
To 
__H 0utPut Sub-Carrier	 Circuit 70 Kc ± 15% 
The problem: 
To design a simple, low cost, low power consump-
tion multichannel pulse height analyzer for balloon 
and rocket investigation of solar neutrons with en-
ergies greater than 10 Mev. Commercially available 
analyzers are prohibitive in cost for modest investi-
gation programs, and present volume and weight 
problems in these applications. 
The solution: 
A pulse height analyzer flight unit costing approxi-
mately $350 (exclusive of labor) and weighing about 
4-1/2 pounds. The unit can operate in a temperature
range of —30° to +70°C and withstand storage tem-
peratures from —50 0
 to +90°C. 
How it's done: 
The device is essentially a pulse height-to-series 
binary converter. The signal input is fed through a 
linear gate to a pulse height-to-time converter circuit 
(PHTC) where the pulse height spectrum is converted 
to a time spectrum by charging a capacitor to the peak 
voltage of the input pulse, and then linearly discharg-
ing the capacitor through a constant current source. 
The PHTC output is a positive pulse referred to as the 
"T pulse", whose duration, which is proportional to 
(continued overleaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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the amplitude of the input pulse, gates on a 2 Mc 
oscillator that in turn feeds a seven-stage cascaded 
binary counter. The counter register stores a binary 
number equivalent to the pulse height input. Analysis 
of the maximum input pulse (3v) requires Msec. 
Upon input pulse termination (approximately 
I .5zsec) the linear gate is closed for 600isec by the 
gate control and a 100.tsec trigger pulse is generated. 
Thus the pulse height-to-time conversion is completed 
before the trigger pulse terminates, and the "scan" is 
generated as soon as the trigger pulse is terminated. 
The "scan" circuits are monostables that sequentially 
generate 100tsec pulses and search the outputs of the 
scalers. If a scaler is left in a "one" state, the scan 
pulse will pass through a diode "and" gate and be fed 
to the output circuit. The sequential scan circuits are 
Co, Cl, C2, C3, and C4. When the C4 scan pulse is 
completed, a gate trigger is generated to reopen the 
linear gate and reset all scalers within 1zsec of linear 
gate reopening. Since the scalers do not operate until 
the input pulse terminates (I .5.tsec), the system can 
analyze an input pulse as soon as the linear gate opens. 
Thus each pulse requires 600sec to analyze and the 
average repetition rate capability of the analyzer is 
1667 pps. 
While the circuit contains 7 scalers, only 5 are used 
to obtain the binary output. The two additional scalers 
permit conversion from 32 to 128 channels and lessen 
ambiguity between adjacent channels. Such ambiguity 
is inherent when a continuous running oscillator is 
"gated" on where the gating is not synchronized, and 
is intolerable when the device is used as a 32-channel 
pulse height analyzer.
1-2ps 
;Ms 
I max 
_j max L_ 
111111
An anticoincidence unit is provided that can be used 
to gate off unwanted pulses before they reach the 
PHTC. The anticoincidence pulse would be +5v and 
precede the input signal by at least 0.25zsec. This 
input can also be used for upper level discrimination if 
an additional discriminator is added to the circuitry. 
When pulse height-to-binary conversion is completed, 
the information is fed to an FM—FM telemetry system. 
The telemetered binary number consists of a series of 
bipolar square waves preceded by a positive trigger 
pulse as shown in the lower figure. The trigger pulse 
synchronizes the ground circuits and Co through C4 
represent bits I through 5, respectively. The bipolar 
pulses are 100sec wide so they may be transmitted 
on a subcarrier with a total bandwidth of 20 kc. 
Note: 
Inquiries concerning this invention may be di-
rected to:
Technology Utilization Officer 
Headquarters 
National Aeronautics and Space 
Administration 
Washington, D.C. 20546 
Reference: B67-10258 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: C. J. Ewald and A. A. Sarkady

of The University of New Hampshire

under contract to

NASA Headquarters
(HQN- 10020) 
Input To PHA 
Pulse Height 
Analyzer 
Linear Sweep Voltage
T Pulse PHTC Output
2 Megacycle Gate Output
Gate • Linear 600	 I	
-1 I	 ps	 I Linear Gate Closed Output 
Scan & 
,	
2	
I U Trigger	
C	
C3	 C4 Trigger 
Scan	 Scan	 Scan Scan	
Scan r	 Pulse 
Gate Trigger 
600 ps Resets	 Scalers & 
Opens linear 
Trigger	 C3	 I 
I
Gate 
Co	 C2 Binary Number 
Level 13 
Telemetry Output 
Level (After 
Demodulation) 
Brief 67-10258 Category 01 


Multichannel pulse height analyzer is inexpensive, features low power requirements

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