Electronics for Distributed Turbine Engine Control and Space Exploration Missions are expected to encounter extreme temperatures and wide thermal swings. In particular, circuits deployed in a jet engine compartment are likely to be exposed to temperatures well exceeding 150 C. To meet this requirement, efforts exist at the NASA Glenn Research Center (GRC), in support of the Fundamental Aeronautics Program/Subsonic Fixed Wing Project, to develop temperature sensors geared for use in high temperature environments. The sensor and associated circuitry need to be located in the engine compartment under distributed control architecture to simplify system design, improve reliability, and ease signal multiplexing. Several circuits were designed using commercial-off-the-shelf as well as newly-developed components to perform temperature sensing at high temperatures. The temperature-sensing circuits will be described along with the results pertaining to their performance under extreme temperature

Culley, Dennis

Elbuluk, Malik

Hammoud, Ahmad

Patterson, Richard L.

NASA Technical Reports Server

  
 
1
Development of a Temperature Sensor for 
Jet Engine and Space Mission Applications 
 
Richard L. Patterson*1, Ahmad Hammoud2, Malik Elbuluk3, Dennis Culley1 
1NASA Glenn Research Center 
21000 Brookpark Road 
Cleveland, OH 44135   USA 
*Ph: 216-433-8166; Fax: 216-433-2221 
Email: Richard.L.Patterson@nasa.gov 
 
2ASRC Aerospace Corporation 
NASA Glenn Research Center 
Cleveland, OH 44135   USA 
 
3University of Akron 
Dept of Electrical & Computer Engineering 
Akron, OH 44325   USA 
 
Abstract 
 
Electronics for Distributed Turbine Engine Control and Space Exploration Missions are expected to 
encounter extreme temperatures and wide thermal swings.  In particular, circuits deployed in a jet engine 
compartment are likely to be exposed to temperatures well exceeding 150 °C.  To meet this requirement, 
efforts exist at the NASA Glenn Research Center (GRC), in support of the Fundamental Aeronautics 
Program / Subsonic Fixed Wing Project, to develop temperature sensors geared for use in high temperature 
environments.  The sensor and associated circuitry need to be located in the engine compartment under 
distributed control architecture to simplify system design, improve reliability, and ease signal multiplexing.  
Several circuits were designed using commercial-off-the-shelf as well as newly-developed components to 
perform temperature sensing at high temperatures.  The temperature-sensing circuits will be described 
along with the results pertaining to their performance under extreme temperature. 
 
Key words 
 
High temperature, temperature sensor, jet engine, space missions 
 
 
 
Extreme Temperature Electronics 
 
Advanced electronic systems emphasize compactness, 
lightweight, increased energy density, reliability, and 
highly efficient operation.  In addition, operation of these 
systems in hostile environments, where extreme 
temperatures are encountered, is anticipated in many 
applications.  For example, jet engine distributed control 
architecture requires sensors and related circuitry to be co-
located with actuators and transducers in the engine’s hot 
zone where temperature can easily exceed +150 °C.  Deep 
space probes destined to Venus and Mercury would also 
encounter high temperatures, and so would the electronics 
designed for use in the Navy’s all-electric boat, and power-
by-wire aircraft.  At the other end of the spectrum, extreme 
cold temperatures are also anticipated in space as well as 
aerospace applications.  An interplanetary probe launched 
to explore the rings of Saturn would experience an average 
temperature of about -183 °C near Saturn, and electronics 
deployed near Pluto, for instance, would be exposed to 
temperatures as low as -229 °C.   Also, systems designed 
for use behind the sun shield on the NASA James Webb 
Space Telescope will require the use of cryogenic detectors 
to capture weak distant signals.  In addition to extreme 
temperature exposure, electronics in applications such as 
lunar surface exploration and earth-orbiting satellites are 
expected to be subjected to repeated thermal cycling 
covering a wide temperature range.  The need for 
electronics capable of operation in extreme temperatures is 
not limited only to space ventures or military applications, 
https://ntrs.nasa.gov/search.jsp?R=20080047731 2019-08-30T05:46:02+00:00Z
  
 
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but it also encompasses many terrestrial industries.  These 
include magnetic levitation transportation systems, power 
generation facilities, down-hole instrumentation for gas and 
oil exploration, automotive, medical imaging, particle 
acceleration and confinement, and Arctic and Antarctic 
exploratory missions.  Besides meeting the environment 
operational conditions, electronics that are able to tolerate 
and operate efficiently in extreme temperatures will negate 
the need for the traditional thermal control elements and 
their associated structures for proper ambient operation.  
This, in turn, would lead to many other benefits including 
decreased overall system mass and size, simplified design, 
and reduced power requirements.  In addition, reduced 
development time and launch costs of space-based systems, 
as well as extended mission operations for longer 
exploration time can be achieved.  Therefore, it is highly 
desirable and vital to have electronic systems capable of 
withstanding and operating reliably in hostile temperature 
environments. 
 
Temperature Sensor 
 
Efforts were carried out to develop and evaluate a 
temperature sensor for the NASA Jet Engine Distributed 
Control Program.  The distributed control architecture 
requires that sensors and associated electronics be co-
located with monitoring and control transducers for engines 
and actuators in very hot environments.  In addition to 
meeting the operational requirements, placement of the 
electronics in the harsh engine compartment allows simpler 
signal multiplexing, improves system performance, and 
avoids or minimizes signal degradation.  The combination 
of GRC high temperature development work for Jet Engine 
Distributed Control and GRC low temperature reliability 
work for the NASA Electronic Parts and Packaging (NEPP) 
Program has yielded a new technical approach for very 
wide temperature electronics design and fabrication 
wherein circuits can operate between -195 °C and +200 °C.  
In addition, there are technical reasons to believe that 
operating temperatures may be extended below -195 °C and 
above +200 °C. 
 
The sensor was designed to sense temperature and to 
produce a digital output consisting of a stream of 
rectangular pulses whose frequency is a function of the 
sensed temperature.  The output frequency will be fed into 
a digital data acquisition system that will give a direct 
readout of the temperature through the use of a look-up 
table, a built-in algorithm, or a mathematical model.  In 
order to develop this sensor circuitry, a literature survey 
was performed to determine the simplest and most efficient 
circuit configuration that could be utilized as a temperature-
to-frequency conversion sensor in extreme temperature 
applications.  A search for commercial-off-the-shelf 
(COTS) electronic parts that could be utilized at extreme 
temperatures was also performed.  A relaxation oscillator 
topology was selected to build the temperature-to-
frequency circuit using an RTD (Resistance Temperature 
Detector) as the temperature-sensing element.  A schematic 
of the circuit is shown in Fig. 1, and the selected COTS 
parts are listed in Table I. 
 
 
Fig. 1.  Schematic of the temperature-to-frequency 
relaxation oscillator circuit. 
 
Table I. 
Parts used in construction of 
the temperature sensor circuit. 
 
Part / 
Company 
Specification 
Temp (°C) 
Features 
Operational 
amplifier / 
Honeywell 
-55 to +225 SOI technology, 
hermetic ceramic DIP 
package 
RTD / U.S. 
Sensor 
-50 to +500 Thin film platinum, 
ceramic package 
Capacitor / 
AVX 
-55 to +125 MLC NPO ceramic 
Resistor / 
Caddock 
+275 High temperature 
precision film resistor 
 
The temperature-to-frequency relaxation oscillator circuit 
was assembled using a high temperature polyimide board, 
Teflon-insulated wire interconnects, and high temperature 
lead-free solder. The circuit employed a Honeywell high 
temperature Silicon-On-Insulator (SOI) operational 
amplifier HT1104.  This device is fabricated with 
Honeywell’s dielectrically isolated high-temperature linear 
HTMOS process, is specified for -55 °C to +225°C 
operation, and is able to perform up to +300 °C[1].  It is a 
14-lead, monolithic amplifier in a hermetic ceramic 
package, and can handle 15 mA output current with a single 
  
 
3
or split supply.  A high temperature precision, thin film 
platinum RTD (Resistance Temperature Detector) [2] was 
selected as the temperature-sensing element, while the other 
passive elements consisted of a multi-layer ceramic (MLC) 
capacitor [3] and three high temperature, precision film 
resistors [4].  For this work, the sensing RTD and the 
relaxation oscillator were all grouped together as a unit, and 
the unit was placed into a temperature controlled chamber. 
The circuit was evaluated at selected test temperatures 
between -195 °C and +200 °C.  A temperature rate of 
change of 10 °C/min and a dwell time of 20 minutes at test 
temperature were used in these investigations.  Circuit 
evaluation was performed by measuring output frequency 
as a function of temperature, variation in the output signal 
duty cycle and rise time, and the circuit supply current.  
The range of the output frequency of the circuit was 
determined by the values of the passive components used.  
A photograph of the actual circuit board is shown in Fig. 2. 
 
 
Fig. 2.  Temperature-to-frequency relaxation oscillator 
circuit board. 
 
Results 
 
A typical output response of the temperature-to-frequency 
conversion circuit, which comprised of a digital pulse train, 
is shown in Fig. 3 at 25 °C.  Those obtained at the high 
temperature of +200 °C and at the cryogenic temperature of 
-195 °C are shown in Fig. 4 and 5, respectively. 
 
 
Fig. 3.  Output waveform of temperature-to-frequency 
circuit at 25 °C.  Vert=5V/div; Horiz=0.1ms/div 
 
 
Fig. 4.  Output waveform of temperature-to-frequency 
circuit at +200 °C.  Vert=5V/div; Horiz=0.1ms/div 
 
 
Fig. 5.  Output waveform of temperature-to-frequency 
circuit at -195 °C.  Vert=5V/div; Horiz=0.1ms/div 
 
The circuit performed very well throughout the test 
temperature range between +200 °C and -195 °C.  As 
expected, the frequency of the output signal fluctuated with 
variation in the sensed temperature; with a frequency of 
about 9.2 kHz at a test temperature of -195 °C and a 
frequency of 2.3 kHz at +200 °C.  This frequency response 
with temperature is depicted in Fig. 6.  The period for the 
pulse train is shown in Fig. 7.  A linear curve-fit has been 
  
 
4
placed over the data points.  For the linear curve-fit, the R 
squared was 0.9994.  No major change was experienced by 
the duty cycle of the output signal as shown in Fig. 8. 
 
 
-200 -100 0 100 200
Temperature (°C)
0
2
4
6
8
10
Fr
eq
ue
nc
y 
(k
H
z)
 
Fig. 6.  Output frequency versus temperature. 
 
 
 
-200 -100 0 100 200
Temperature (°C)
0
100
200
300
400
500
P
er
io
d 
(μs
)
Fig. 7.  Pulse train period versus temperature. 
-200 -100 0 100 200
Temperature (°C)
0
20
40
60
80
100
D
ut
y 
C
yc
le
 (%
)
 
Fig. 8.  Duty cycle of output signal as a function of 
temperature. 
 
While the rise time of the output signal held steady value 
between 25 °C and +200 °C, it did, however, undergo a 
very slight increase as the temperature was decreased below 
room temperature, as shown in Fig. 9.  The rise time 
increased from a value of 1.3 µs at 25 °C to a value of 4.2 
µs at -195 °C.  The supply current of the circuit remained 
between 4 to 8 mA throughout these tests.  Fig. 10 shows 
supply current as a function of temperature. 
 
 
-200 -100 0 100 200
Temperature (°C)
0
2
4
6
8
R
is
e 
Ti
m
e 
(μs
)
 
Fig. 9.  Rise time of output signal versus temperature. 
 
  
 
5
-200 -100 0 100 200
Temperature (°C)
0
4
8
12
16
20
Su
pp
ly
 C
ur
re
nt
 (m
A
)
 
Fig. 10.  Circuit supply current as a function of 
temperature. 
 
Conclusions 
 
A temperature-to-frequency relaxation oscillator circuit was 
constructed using COTS parts for application under 
extreme temperatures.  The circuit employed a high 
temperature SOI operational amplifier, a thin-film platinum 
RTD, NPO multi-layer ceramic capacitors, and precision 
film resistors. Although the circuit was designed mainly for 
a hot jet engine environment, it was evaluated also for 
potential use under cryogenic conditions.  Performance of 
the oscillator circuit was investigated in terms of its 
frequency response, pulse train period, variation in output 
signal duty cycle and rise time, and supply current under a 
wide temperature range between -195 °C and +200 °C.  
The prototype circuit performed well throughout this 
temperature range in producing a pulse train whose period 
was proportional to the sensed temperature, and no major 
changes were observed in its characteristics, i.e. duty cycle 
and rise time of the output signal, as a result of change in 
test temperature.  In addition, all of the individual parts 
exhibited no physical or packaging damage due to the 
extreme temperature exposure.  It can be concluded, 
therefore, that all the COTS parts used in designing the 
circuit exhibited good performance under wide temperature 
swing, and these preliminary results suggest that the circuit 
has good potential for use in both hot and cold temperature 
environments.  Issues such as long-term exposure to 
extreme temperatures, thermal cycling, and mechanical 
vibrations; that are typically encountered in jet engine 
environs, need to be addressed to establish reliability of the 
circuit and to better determine its suitability for use in 
hostile space and aerospace applications.  Future work will 
address development of a sensor for higher temperature 
measurement in which the sensing RTD can be placed in 
hotter environments and processing electronics can be 
placed in cooler environments very near the sensing RTD. 
 
Acknowledgment 
 
This work was partially performed under the NASA Glenn 
Research Center, GESS-2 Contract # NNC06BA07B.  
Support was provided by the NASA Fundamental 
Aeronautics Program / Subsonic Fixed Wing Project / 
Distributed Engine Control Task and by the NASA 
Electronic Parts and Packaging (NEPP) Program. 
 
References 
 
[1] Honeywell Company, “High Temperature Quad Operational 
Amplifier HT1104”, Datasheet 900134 Rev. B, 9-03. 
[2] U.S. Sensor, “Thin Film Platinum RTD’s”, Data Sheet. 
[3] AVX Corp., “SMPS Stacked MLC Capacitors”, Data Sheet. 
[4] Caddock Electronics, Inc. “Type MM and ML Precision Film 
Resistors”, Data Sheet 28-IL124.1004. 
 
 
 


Development of a Temperature Sensor for Jet Engine and Space Mission Applications

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