Lisa C. Martin, John D. Wrbanek, and Gustave C. Fralick

Glenn Research Center, Cleveland, Ohio

Thin Film Sensors for Surface Measurements

NASA/TM—2001-211149

September 2001
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Prepared for the

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cosponsored by the IEEE AES, NASA Glenn, and OAI

Cleveland, Ohio, August 27–30, 2001

Lisa C. Martin, John D. Wrbanek, and Gustave C. Fralick

Glenn Research Center, Cleveland, Ohio

Thin Film Sensors for Surface Measurements

NASA/TM—2001-211149
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Available electronically at http://gltrs.grc.nasa.gov/GLTRS
NASA/TM2001-211149 1

THIN FILM SENSORS FOR SURFACE MEASUREMENTS

Lisa C. Martin, John D. Wrbanek, and Gustave C. Fralick

National Aeronautics and Space Administration

Glenn Research Center

Cleveland, Ohio 44135

ABSTRACT

Advanced thin film sensors that can provide accurate 

surface temperature, strain, and heat flux measurements 

have been developed at NASA Glenn Research Center. 

These sensors provide minimally intrusive 

characterization of advanced propulsion materials and 

components in hostile, high-temperature environments as 

well as validation of propulsion system design codes. 

The sensors are designed for applications on different 

material systems and engine components for testing in 

engine simulation facilities. Thin film thermocouples 

and strain gauges for the measurement of surface 

temperature and strain have been demonstrated on 

metals, ceramics and advanced ceramic-based composites 

of various component configurations. Test environments 

have included both air-breathing and space propulsionbased engine and burner rig environments at surface 

temperatures up to 1100°C and under high gas flow and 

pressure conditions. 

The technologies developed for these sensors as well as 

for a thin film heat flux gauge have been integrated into a 

single multifunctional gauge for the simultaneous realtime measurement of surface temperature, strain, and 

heat flux. This is the first step toward the development of 

smart sensors with integrated signal conditioning and 

high temperature electronics that would have the 

capability to provide feedback to the operating system in 

real-time.

A description of the fabrication process for the thin film 

sensors and multifunctional gauge will be provided. In 

addition, the material systems on which the sensors have 

been demonstrated, the test facilities and the results of the 

tests to-date will be described. Finally, the results will be 

provided of the current effort to demonstrate the 

capabilities of the multifunctional gauge.

INTRODUCTION

Sensors developed for aeronautic and aerospace research 

applications must be able operate in environments where 

stress and temperature gradients are high and 

aerodynamic effects need to be minimized. To meet 

these needs, sensors in thin film form are being 

developed at NASA Glenn Research Center for surface 

measurement on various material systems.1 Thin film 

sensors provide a minimally intrusive means of 

measuring surface parameters in engine systems such as 

temperature, strain and heat flux that are needed to 

evaluate advanced materials and components and to 

provide experimental verification of computational 

models. Unlike conventional wire sensors, thin films do 

not require machining the surface and therefore leave 

intact the structural integrity of the engine component 

being measured. The thin films are vacuum deposited 

directly onto the surface and have thicknesses on the 

order of a few micrometers (μm) which are orders of 

magnitude less than wire sensors. As a result, thin film 

sensors add negligible mass to the surface and cause 

minimal disturbance to the gas flow over the surface. 

Thin film sensors, therefore, have minimal impact on the 

thermal, strain, and vibration patterns that exist in the 

operating environment.

The thin film thermocouple (TFTC) has been developed 

and demonstrated on several material systems for jet 

aircraft and space-based engine applications, including 

superalloys, ceramics, intermetallics, and ceramic matrix 

composite materials. TFTCs have been tested in 

laboratory furnaces tests as well as in harsh 

environments, including gas turbine and 

hydrogen/oxygen engine environments under both low 

and high pressure conditions, a high heat flux facility and 

a diesel engine environment.1-7 The test temperatures 

have ranged from 1000–1500°C.

The strain gauges developed at NASA GRC for high 

temperature applications are palladium-13 wt% 

chromium (PdCr). This alloy is structurally stable up to 

elevated temperatures and its apparent strain versus 

temperature characteristic is linear, repeatable and not 

sensitive to heating and cooling rates. PdCr gauges have 

been demonstrated in both dynamic and static strain 

testing on superalloy, ceramic, and ceramic matrix 

composite components of engines and aircraft structures 

to 1100°C.1,8

A thin film heat flux gauge developed at NASA GRC is 

based on measurement of temperature differences which 

in this case is measured across two locations on the

substrate surface. Since the temperature drop is small, the 

differential signal output is increased by placing a 

number of thermocouple pairs connected in series. This is 

achieved with a circular thermopile with two thicknesses 

of a ceramic insulator. The advantages the thin film heat 
NASA/TM2001-211149 2

lux gauge offers over conventional gauges include the 

capability to measure steady as well as transient heat 

fluxes, excellent transient response characteristics, 

minimal obstruction to thermal as well as physical flow, 

high temperature capability, and good sensitivity due to 

large output signal.9,10

The technologies developed for the thermocouple, strain 

gauge, and heat flux sensors are being integrated into a 

single multifunctional gauge for the simultaneous realtime measurement of surface temperature, strain, and 

heat flux. This is the first step toward the development of 

smart sensors with integrated signal conditioning and 

high temperature electronics that would have the 

capability to provide feedback to the operating system in 

real-time.

SENSOR DESIGN

Electrical Insulation

The thin film sensors are fabricated in a Class 1000 

Microfabrication Clean Room which contains sputter 

deposition and evaporation systems, wire bonding 

systems, etching capabilities, photolithography 

equipment, and a surface profilometer. The thin film 

sensor fabrication process must be tailored to the 

substrate material and intended end application in order 

to ensure good adhesion as well as no chemical 

interaction between the sensor and substrate material. 

Figure 1 is a schematic diagram of the sensor layers on 

both electrically insulating and electrically conducting 

substrates. Electrically insulating materials allow the 

sensor to be deposited directly onto the substrate as

long as there is no chemical interaction between the 

sensor and substrate materials. For applications that 

require protection from the operating environment, a 

protective overcoat, typically aluminum oxide, is sputter 

deposited or evaporated onto the sensor to a thickness of 

approximately 2-3 μm. 

In the case of electrically conductive ceramic materials 

such as silicon carbide, the substrate is thermally

Figure 2. PdCr thin film strain gauges: dynamic strain

gauge (left) and static strain gauge (right).

oxidized to form a stable, adherent silicon dioxide layer. 

An additional layer of alumina is sputter deposited or 

electron beam evaporated onto the surface to fill any 

pinholes or cracks that are present in the grown oxide 

which then enables the film to reach the required 

insulation resistance. The thickness of the thermally 

grown silicon dioxide and sputter deposited aluminum 

oxide are approximately 2-3 μm and 5-8 μm, 

respectively. The sensor elements are then fabricated on 

the oxide layer followed by a protective overcoat, if 

needed.

In the case of electrically conductive metal substrates 

such as superalloy materials, an MCrAlY bond coat is 

deposited via electron beam deposition or sputter 

deposition. M may be Fe, Co, Ni, or a combination of Co 

and Ni. This coating forms a stable, adherent, electrically 

insulating alumina layer when heat treated. Again, an 

additional layer of alumina is deposited to complete the 

insulation layer and the sensor and protective overcoat 

can then be deposited.

Sensor Elements

The thin film thermocouples are standard Type R 

thermocouples (platinum-13% rhodium vs. platinum) and 

are typically patterned with stenciled shadow masks and 

sputter deposited to approximately 5 μm thickness. A 

process has also been developed using photolithography 

methods involving a lift-off process.

The PdCr strain gauge is prepared by 

sputter deposition of approximately 8 μm 

of PdCr which is then patterned 

via photolithography and chemical etching. 

The dynamic strain gauge is presented in 

Figure 2. For static strain applications, a 

temperature compensator element of 

platinum is used to minimize the 

temperature effect on the PdCr resistance 

change. PdCr has a higher, but constant, 

temperature coefficient of resistance than 

that permitted for a static strain gauge. 

The sputter-deposited platinum element is 

Figure 1. Schematic diagram of thin film sensors on various substrate 

materials.

Protective Overcoat

Sensor

Sputtered or E-Beam 

Alumina

Thermally Grown 

Alumina

MCrAlY Coating

Superalloy

Substrate

Superalloys

Protective Overcoat

Sensor

Sputtered or E-Beam 

Alumina

Thermally grown Silica

Electrically

Conductive

Ceramic Substrate

Silicon Carbide

Protective Overcoat

Sensor

Electrically

Insulating

Substrate

Silicon nitride

Aluminum nitride

f
NASA/TM2001-211149 3

5 μm thick and is patterned with a stenciled shadow 

mask. It is located around the PdCr gauge grid and 

connected to the adjacent arm of a Wheatstone bridge 

circuit to minimize the temperature effect (Figure 2).11

The thin film heat flux gauge is a planar thermopile 

arranged in a circular pattern consisting of 40 

thermocouples in series (Figure 3). The thermopile is 

used to measure temperature difference between the 

inside and outside junctions.9,10 The use of a thermopile 

allows the output signal to be multiplied by the number 

of thermocouple pairs. Since a thin film insulator 

produces a small temperature difference, the thermopile 

is effective in boosting the output signal. The elements 

are platinum and platinum-10% rhodium. To create a

temperature difference, dielectric films (either silicon 

dioxide or aluminum oxide) of two thicknesses are 

deposited on the two thermopile junctions (Figure 4). 

The incident heat flux (

.

Q ) is determined with the 

equation:

1 2

1 2 .

x x

T T Q K −

− =

where K is the coefficient of thermal conductivity,

(T1 – T2) is the temperature difference across the two 

layers of insulator, and x1 and x2 are the thicknesses of 

the two insulator layers.

The sensor is patterned with microlithography, lift-off, 

etch processing and sputter deposition.

X2 = 5 μm 

Ceramic

X1 = 1 μm 

Ceramic

T1 – T2

Thermopile

Figure 3. Planar thermopile concept for measuring 

heat flux.

Lead Wire Attachment

Parallel gap welding is used to attach 75 μm lead wires to 

the thin film sensors. Platinum and platinum-rhodium 

wires are used for the Pt and Pt-Rh elements of 

Figure 4. Concept for heat flux measurement

the thermocouples and heat flux gauges and Pt wires are 

used for both PdCr and Pt strain gauge elements. 

When needed, high temperature ceramic cement is used 

to further secure the lead wires to the substrate.

SENSOR APPLICATIONS

Thermocouples

Thin film thermocouples have been fabricated and tested 

on a number of substrate systems including nickel-based 

superalloys, silicon carbide, silicon nitride, mullite and 

aluminum oxide ceramics, ceramic matrix composites 

(CMC) and intermetallics. The sensors have been 

demonstrated on various test component configurations 

and in different test environments.

Thin film thermocouples were demonstrated on Space 

Shuttle Main Engine (SSME) turbine blades (Figure 5) in 

a test facility designed to simulate the highly transient 

temperature and pressure conditions of the SSME high 

pressure fuel turbopump environment. The blades were 

Ni-based superalloys as were a series of flat substrates 

instrumented with thin film thermocouples and tested in 

hydrogen-fueled burner rigs. The films proved to be 

highly adherent and durable to the 1000°C test 

conditions.

Thin film thermocouples have also been used in 

evaluating advanced ceramic matrix composite materials 

of various test hardware configurations designed to meet 

propulsion capability goals of several development 

programs.1,4 A hydridopolysilazane fiber/silicon carbide 

matrix CMC liner was tested with thin film 

thermocouples in a jet-fueled burner rig operating under 

pressures of 0.7 to 2 MPa and gas temperatures of 

1500°C. Temperature data up to 1100°C was obtained

T1 T2

K

Temperature

Sensors

K

Substrate

X1

X2

Q

Ceramic 

Thermal 

Insulator
NASA/TM2001-211149 4

Figure 5. Thin film thermocouples on 

SSME turbine blade.

for over 25 hours of testing. Several SiC fiber/SiC 

matrix ceramic matrix composites panels, cylinders, and 

combustor liners have also been instrumented with thin 

film thermocouples and successfully tested in the same 

combustor test facility. The typical initial failure mode 

for the sensors is the detachment of the lead wires from 

the sensor film. This issue is currently being addressed.

Strain Gauges

Thin film PdCr strain gauges have been fabricated and 

tested on nickel-based superalloys, silicon nitride and 

aluminum oxide ceramics, and SiC/SiC ceramic matrix 

composites. Test environments have included air 

furnaces, a heat flux arc lamp, spin rig, and jet-fueled 

combustor test facility.1

The requirements for a useful strain gauge may be 

different dependent upon the application for a dynamic or 

static strain measurement. In the case of dynamic strain 

measurements during which the strain rate of change is 

much larger compared with the temperature change rate, 

the permissible apparent strain sensitivity of the gauge 

can be high as compared to static strain measurement. 

The general requirements for a dynamic strain gauge are 

that its apparent strain sensitivity is less than 

100 microstrain με/°C and its drift strain rate at the 

application temperature is less than 500 με/hour.12

However, for static strain measurements over long 

periods of time, both the temperature and strain may 

vary. Therefore, for a required accuracy of 10% for static 

strain measurement in the range of 2000 με, the total 

apparent strain and drift strain should be smaller than 

200 με so as to be neglected, or repeatable to within 

200 με so it can be corrected.

The apparent strain of a PdCr dynamic strain gauge is 

stable and repeatable between thermal cycles to 1100°C 

when connected to a Wheatstone bridge circuit in a 

quarter bridge configuration.8 The apparent strain 

sensitivity is approximately 85 με/°C and the drift strain 

at 1100°C is less than the permissible value of 

500 με/hour. The resulting apparent strain characteristic 

of a PdCr static strain gauge connected to a Wheatstone 

bridge circuit in a half bridge configuration is stable and 

repeatable to within +200 με between thermal cycles to 

1100°C with a sensitivity less than 3.5 με/°C in the entire 

temperature range. The apparent strain of the PdCr 

compensated thin film gauge can be corrected to within 

+200 με if the temperature measurement uncertainty is 

within 57°C. The gauge is stable and responds linearly to

mechanical loads up to 1050°C. This is 500°C above the 

usable temperature for conventional NiCr strain gage 

technology. The strain sensitivity, or gauge factor, for 

PdCr decreases approximately 22% from room 

temperature to 1050°C.

PdCr thin film strain gauges have been demonstrated in 

an air furnace up to 1100°C and in a heat flux calibrator 

with heating rates up to 1100°C/sec and heat flux up to 

2 MW/m2. The dynamic gauges were also fabricated on 

an advanced silicon nitride turbine blade and survived 

tests up to 42,500 rpm and fatigue tests at +2000 με up to 

1000°C for a million cycles. The gauges have also been 

demonstrated on SiC/SiC ceramic matrix composite 

components in a jet-fueled burner rig operating at surface 

temperatures of approximately 1100°C.

A weldable PdCr thin film strain gauge was developed 

for applications that do not allow a gauge to be sputtered 

directly on to the component because the component is 

too large to be accommodated in the deposition rig or 

when gauge installation must be performed in the test 

field. The gauge is first deposited on a metal shim that 

has a similar coefficient of thermal expansion to that of 

the substrate material. The shim is then welded onto the 

test article. The mechanical response of the weldable 

gauge is similar to that of a direct-deposited gauge in that 

it is linear to the mechanical load and does not cause 

delay in strain transfer.8

Heat Flux Gauges

The thin film heat flux gauges have been demonstrated 

on silicon, aluminum oxide, silicon nitride, and nickelbased superalloys.10 Test environments include exposure 

to radiation from a furnace to 900°C providing a low heat 

flux of 0.1 Mw/m2

. The output of the sensor was about 
NASA/TM2001-211149 5

30 microvolts. The gauge has also been tested in a heat 

flux arc lamp calibrator at temperatures up to 900°C and 

heat flux up to 1.5 Mw/m2 with an output of up to almost 

4 millivolts.

The sensor has also been fabricated on the curved surface 

of a SSME turbine blade (Figure 6).10 Because many of 

the intended applications are on engine components that 

have complex shapes, these sensors must be able to be 

fabricated on curved surfaces. The fine lines and 

dimensions of these heat flux gauges along with the 

multistep patterning process makes this effort 

challenging. 

Figure 6. Thin film heat flux gauge on 

SSME turbine blade.

MULTIFUNCTIONAL SENSOR

Design

In order to address the call for smart sensors that not only 

track the performance of a component during operation 

but also provide feedback in real time, the first step has 

been taken by integrating the technologies discussed thus 

far into a single, multifunctional gauge. This provides a 

single array for real-time measurement of temperature, 

strain, and heat flux with the potential for gas flow 

measurement as well. 

For the magnitude and direction of both strain and flow, a 

triangular strain gauge has been designed. The patented 

design modified a rosette pattern strain gauge by linking 

the three legs of the rosette together and powering them

θ

εM

G1

G2

G3

60°

60°

60°

I+

IV1

V2

V3

V4

Figure 7. Concept for triangular strain gage

component of Multifunctional Sensor.

under a single constant current source.13,14 A schematic 

of the design is shown in Figure 7.

The strain applied to the triangular gauge is sensed as 

individual strain components by each of the three legs 

of the rosette. These strain components are determined 

by measuring the increase or decrease of the voltage drop 

along each leg due to the applied strain. The voltage 

drop on each leg is the sum of the strain component in 

that direction and the apparent strain with the assumption 

that the apparent strain is the same for each leg. The three 

legs provide three equations and three unknowns: strain 

magnitude, strain direction, and apparent strain. In 

principal, the apparent strain is eliminated and the main 

parameters of interest, strain magnitude and direction, are 

obtained by solving the equations.

This gauge design allows measurement of strain 

magnitude and direction but with half the lead wires 

required for a standard rosette gauge. In addition, by 

measuring the resistance change in the gauge under high 

current conditions, the sensor can be calibrated for flow 

measurement as an anemometer.13

Both PdCr and platinum are being utilized as gauge 

materials. PdCr is limited to applications below 1100°C 

whereas platinum is usable for higher temperature use.

Figure 8 shows the complete gauge design incorporating 

the triangular strain gauge, heat flux gauge and 

thermocouple. The heat flux gauge and thermocouple

incorporate the design discussed earlier in this paper. 

The element materials for both the heat flux gauge and
NASA/TM2001-211149 6

Triangular 

Strain 

Gauge

Heat Flux 

Gauge

Thermocouple

Figure 8. Design of Multifunctional Sensor.

the thermocouple are platinum-13% rhodium and 

platinum. The entire gauge is enclosed in a triangle 

approximately 1.5 cm on a side with line widths of 

50 μm. The gauges are fabricated with photolithography 

techniques, lift-off, etching, and metal masking.

Figure 9 shows three prototype gauges on constant 

strain alumina beams. Figure 10 shows a close-up of 

the most recent prototype of the gauge.

Prototype Testing

Various prototypes of the gauge have been bench tested 

for all of the parameters except flow.13 The gauge was 

tested for strain response in the Dynamic Load Test Rig. 

Measurements of both the static and dynamic response of 

the sensors were made and the strain magnitude was 

measured to an accuracy of within +10% of the nominal 

value. The strain angle was measured to an accuracy 

of within +1o of the nominal value. The sensor reacted 

to heat flux as predicted when exposed to a heat gun

flowing perpendicular to the surface. The resulting 

signal data is shown in Figure 11. Calibration, transient, 

and frequency response of the heat flux portion of the 

sensor is described in Reference 15. Longitudinal flows 

over the sensor produced twice the response of transverse 

flows, demonstrating the feasibility of measuring flow. 

Future testing will include measuring all of the 

parameters simultaneously from a single prototype 

sensor. Additionally, the sensor will be fabricated on an 

engine component and tested in the lab as well as in 

harsh test environments. Alternate materials for the 

sensor elements will be explored as the sensor is pushed

for use in higher temperature applications. Ceramic 

thermocouple and strain gauge materials are being 

investigated and may replace the metals currently being 

used. An electronics package is to be developed to allow 

the sensor to become “smart” without the need for PCbased software. Additionally, the sensor is to be 

developed as a transferable gauge, similar to the weldable 

strain gauge described earlier.

SUMMARY

The ongoing development of thin film sensors is 

addressing the need for advanced measurement 

techniques for propulsion systems. The technology for 

measuring temperature, dynamic and static strain, and 

heat flux has been demonstrated on numerous material 

systems and in several test environments. These 

technologies are currently being incorporated into a 

single, multifunctional system that is minimally intrusive 

and usable in harsh test environments. These 

systems will be designed to be smart, stand-alone 

systems with integrated electronics. Additionally, lead 

wire attachment techniques are being addressed in order

to improve durability and reliability. Finally, sensors

Figure 9. Prototype gauges on constant strain alumina beams.
NASA/TM2001-211149 7

Figure 10. Close-up of most Multifunctional

Sensor prototype.

Heat Flux Response on 

Second Prototype Sensor

-60

-40

-20

0

20

40

60

80

100

120

0 100 200 300 400

Time (seconds)

HF Signal (μV)

Heat On Heat Off

Figure11. Heat flux response from Multifunctional

Sensor prototype.

that can be used to even higher temperatures (>1200°C) 

are being explored to address the demands being made by 

advanced aeropropulsion research for higher use 

temperatures.

REFERENCES

1). Lei, J.F., Martin, L.C., and Will, H.A., 1997, 

“Advances in Thin Film Sensor Technologies for Engine 

Applications”, NASA TM–107418, Turbo Expo ’97, 

Orlando, FL, June.

2). Holanda, R., 1992, “Development of Thin Film 

Thermocouples on Ceramic Materials for Advanced 

Propulsion System Applications,” 7th International 

Symposium on Temperature: Its Measurement and 

Control in Science and Industry, Toronto, Canada, April.

3). Martin, L.C. and Holanda, R., 1994, “Applications of 

Thin Film Thermocouples for Surface Temperature 

Measurement,” NASA TM–106714.

4). Martin, L.C. and Will, H.A., 1995, “Testing of Thin 

Film Thermocouples on Ceramic Matrix Composites in a 

Burner Rig,” NASA CP–10178, Paper 39.

5). Grant, H.P., Przybyszewski, J.S., and Claing, R.G., 

1981, “Turbine Blade Temperature Measurements Using 

Thin Film Temperature Sensors,” PWA–5604–31, NASA 

CR–165201.

6), Holanda, R., Anderson, R.C., and Liebert, C.H., 

1993, “Heat Flux Measurements on Ceramics with Thin 

Film Thermocouples,” SEM Fall Conference Proceeding 

of Structural Testing Technology at High Temperature, 

p. 78–87.

7). Kim, S. and Barrows, R.F., 1988, “Prototype Thin 

Film Thermocouple/Heat Flux Sensor for a CeramicInsulated Diesel Engine,” DOE/NASA/50162–1, NASA 

TM–100798.

8). Lei, J.-F., 1995, “High Temperature Thin Film Strain 

Gauge,” British Society for Strain Measurement 1995 

Annual Conference Proceeding, p. 13–16.

9). Bhatt, H., Zeller, M., and Will, H.A., 1992, “Novel 

Thin-Film Heat Flux Sensors,” NASP Conference, 

Orlando, FL, Dec.

10). Will, H.A. and Bhatt, H., 1994, “Status of Thin Film 

Heat Flux Sensors,” NASA CP–3282, pp.127–132.

11). Lei, J.-F., Englund, D.R., and Croom, C., 1991, “The 

Temperature Compensation Technique for a PdCr 

Resistance Strain Gauge,” SEM Fall Conference for 

Structural Testing Technology at High Temperature 

Proceeding, pp. 190–196.

12). Grant, H.P., Przybyszewski, J.S., Anderson, W.L., 

and Claing, R.G., 1983, “Thin Film Strain Gauge 

Development Program,” NASA CR–174707.

13). Wrbanek, J.D., Fralick, G.C., and Martin, L.C., 

2001, “A Thin Film Multifunction Sensor for Harsh 

Environments,” AIAA–2001–3315.

14). Lei, J.-F., Fralick, G.C., and Krasowski, M.J., 1999, 

“Microfabricated Multifunction Strain-Temperature 

Gauge,” U.S. Patent 5,979,243.

15). Cho, C.S., Fralick, G.C., and Bhatt, H.D., 1997, 

“Steady-State and Frequency Response of a Thin-Film 

Heat Flux Gauge,” J. of Spacecraft and Rockets, Vol. 34, 

No. 6, pp.792–798.
This publication is available from the NASA Center for AeroSpace Information, 301–621–0390.

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Technical Memorandum

Unclassified

National Aeronautics and Space Administration

John H. Glenn Research Center at Lewis Field

Cleveland, Ohio 44135–3191

1. AGENCY USE ONLY (Leave blank)

10. SPONSORING/MONITORING

 AGENCY REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546–0001

Available electronically at http://gltrs.grc.nasa.gov/GLTRS

September 2001

NASA TM—2001-211149

E–13001

WU–708–72–45–00

13

Thin Film Sensors for Surface Measurements

Lisa C. Martin, John D. Wrbanek, and Gustave C. Fralick

Thin film sensor; Strain; Thermocouples; Temperature;

Instrumentation; Harsh environment

Unclassified -Unlimited

Subject Category: 35 Distribution: Nonstandard

Prepared for the 2001 19th International Congress on Instrumentation in Aerospace Simulation Facilities (ICIASF 2001)

cosponsored by the IEEE AES, NASA Glenn, and OAI, Cleveland, Ohio, August 27–30, 2001. Responsible person,

John D. Wrbanek, organization code 5510, 216–433–2077.

Advanced thin film sensors that can provide accurate surface temperature, strain, and heat flux measurements have been developed at

NASA Glenn Research Center. These sensors provide minimally intrusive characterization of advanced propulsion materials and

components in hostile, high-temperature environments as well as validation of propulsion system design codes. The sensors are

designed for applications on different material systems and engine components for testing in engine simulation facilities. Thin film

thermocouples and strain gauges for the measurement of surface temperature and strain have been demonstrated on metals, ceramics

and advanced ceramic-based composites of various component configurations. Test environments have included both air-breathing

and space propulsion-based engine and burner rig environments at surface temperatures up to 1100 °C and under high gas flow and

pressure conditions. The technologies developed for these sensors as well as for a thin film heat flux gauge have been integrated into

a single multifunctional gauge for the simultaneous real-time measurement of surface temperature, strain, and heat flux. This is the

first step toward the development of smart sensors with integrated signal conditioning and high temperature electronics that would

have the capability to provide feedback to the operating system in real-time. A description of the fabrication process for the thin film

sensors and multifunctional gauge will be provided. In addition, the material systems on which the sensors have been demonstrated,

the test facilities and the results of the tests to-date will be described. Finally, the results will be provided of the current effort to

demonstrate the capabilities of the multifunctional gauge.