Pulse echo ultrasonic system automatically determines the temperature in the core of a nuclear rocket engine by measuring the transit time of an acoustic pulse in a wire sensor. The measurement is based on the fact that the speed of sound in the sensor material is a function of temperature

Carnevale, E. H.

Lynnworth, L. C.

English

Pulse echo ultrasonic system for automatically determining temperature by measuring round trip transit times in wire sensor

NASA Technical Reports Server

Ultrasonic temperature measuring device Final report

August 1968
	 Brief 68-10319 
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. 
Ultrasonic Temperature Measuring Device 
Transmit/Receive Unit with 
Digital Display of Transit 
Time in Sensor
Time in Sensor 
	
I	 iii jij ii	 J	 Ultrasonic Pulse Transit Hec05
II 
To Damping Pad S	 or to Second	 Sensor Lead-in and	 -	 Magnetostrictive 1 Sensor	 Alloy  I	 I	 p 
	
I	 T	 R 
	
I	 I 
	
I	 Lead-in Wire	 L - ----------------
Transducer	 High Temperature 
Environment 
The problem: 
One of the more important measurements required 
in nuclear rocket engine technology is the measure-
ment of temperature in the core of the engine. This 
measurement has proven to be extremely difficult 
because of the high temperatures involved (==5000'R), 
because of compatibility problems with some of the 
materials involved (graphite and hydrogen) and be-
cause of the intense and sustained neutron and 
gamma fluxes. Additional difficulties stem from the 
high ambient noise, shock, and vibration levels en-
countered in some locations, the high degree of 
accuracy and the response time required, possibility of 
temperature overshoot, high pressure, accessibility, 
geometrical restrictions, etc. 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
The solution: 
A pulse echo ultrasonic system which automatically 
determines temperature by measuring the transit 
time of an acoustic pulse in a wire sensor. The meas-
urement is based on the fact that the speed of sound 
in the sensor material is a function of temperature. 
How it's done: 
The principle elements of the ultrasonic system, 
shown in the figure include a transducer, a lead-in 
wire, a sensor, and an automatic electronic instrument 
for producing pulses and measuring the transit time 
between the two reflected pulses. A pulse is produced 
electrically in the transmitting coil T. This pulse is 
converted magnetostrictively to an acoustic pulse 
which travels down the lead-in wire to the sensor. 
(Continued overleaf) 
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000319 2020-03-12T06:13:16+00:00Z
The pulse is partially reflected from that point of the 
wire sensor where the acoustic impedance is 
changed. The acous1ical imjedance change in the 
sensor can be a kink, bend, or abrupt diameter 
change. The remainder of the pulse continues along 
the sensor and is reflected from the end of the sensor. 
The two reflected pulses travel back up the lead-in 
wire to the receiving coil R where they are converted 
in an inverse magnetostrictive manner to electrical 
pulses. The time between the two pulses is inversely 
proportional to the speed of sound in the sensor which 
is a function of sensor temperature. 
The magnetostrictive transducer is made by winding 
a coil on a nickel alloy wire. In axially-magnetized 
wires, an extensional wave is propagated in the wire. 
This device averages 10 measurements of transit 
time in the sensor to ±0.1 isec., and provides this 
average reading in digital and analog form with an 
instrument response time of 0.1 sec. 
Notes: 
I. The ultrasonic thermometer offers several ad-
vantages over thermocouples, depending upon the 
application. These advantages are due partly to 
the greater choice of ultrasonic sensor materials. 
Only one material is required for the sensor 
instead of two as is required by a thermocouple. 
The ultrasonic thermometer does not require elec-
trical insulation, thereby eliminating the shunting
errors experienced by small thermocouples at high 
temperatures. The sensor may be installed bare in 
electrically conducting media if the sensor materia 
is compatible with the environment. If a pressure 
seal is required, the lead-in wire can be brazed or 
welded to a sealing diaphragm which is thin com-
pared to wavelength. Electrical feedthroughs 
or compression seals can also be used if compati-
ble with the environment. The ultrasonic sensor, 
composed of only one material, is not subject to 
calibration shifts which, in thermocouples, are 
caused by diffusion of material from one leg into 
the other. 
2. Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B68-10319 
Patent status: 
No patent action is contemplated by NASA. 
Source: L. C. Lynnworth and E. H. Carnevale 
of Parametrics, Inc. 
under contract to 
Lewis Research Center 
(LEW- 10446) 
Brief 68-10319	 Category 01


Ultrasonic temperature measuring device

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