Patrick M. Flanagan

Cleveland State University, Cleveland, Ohio

John Lekki

Glenn Research Center, Cleveland, Ohio

A Self-Diagnostic System for the

M6 Accelerometer

NASA/TM—2001-211156

November 2001

AIAA–2001–3318
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NASA/TM—2001-211156

November 2001

National Aeronautics and

Space Administration

Glenn Research Center

Prepared for the

37th Joint Propulsion Conference and Exhibit

cosponsored by the AIAA, SAE, AIChE, and ASME

Salt Lake City, Utah, July 8–11, 2001

AIAA–2001–3318

Patrick M. Flanagan

Cleveland State University, Cleveland, Ohio

John Lekki

Glenn Research Center, Cleveland, Ohio

A Self-Diagnostic System for the

M6 Accelerometer
Available from

NASA Center for Aerospace Information

7121 Standard Drive

Hanover, MD 21076

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22100

Available electronically at http://gltrs.grc.nasa.gov/GLTRS
NASA/TM—2001-211156 1

A Self-Diagnostic System for the M6 Accelerometer 

Patrick M. Flanagan

Cleveland State University 

Cleveland, Ohio 44115

John Lekki

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135

Abstract 

The design of a Self-Diagnostic (SD) 

accelerometer system for the Space 

Shuttle Main Engine is presented. This 

retrofit system connects diagnostic 

electronic hardware and software to the 

current M6 accelerometer system. This 

paper discusses the general operation of 

the M6 accelerometer SD system and 

procedures for developing and evaluating 

the SD system. Signal processing 

techniques using M6 accelerometer 

diagnostic data are explained. Test 

results include diagnostic data responding 

to changing ambient temperature, 

mounting torque and base mounting 

impedance. 

Background 

Self-diagnostic accelerometers are needed 

when the accuracy of data are mission 

critical. This is especially important in 

“smart” aerospace systems where a 

computer system makes judgments and 

takes action during flight, based on data 

from these sensors. Smart systems need 

real-time information on accelerometer 

performance including soft failures, to be 

reliable enough for aerospace applications. 

Accelerometer malfunctions such as 

improper or shifting mounting torque 

levels and non-catastrophic damage can 

produce poor data. These failures should 

be identified immediately so that 

appropriate action can be taken by a 

smart aerospace system. The SD system 

has been researched with the goal to 

improve the real-time performance of 

smart sensor systems with the reliability 

that is necessary for implementation in 

aerospace vehicles. 

A SD system makes use of the 

accelerometer’s piezoelectric crystals to 

measure both acceleration and diagnostic 

data. This system does not change the 

structure or the acceleration measurement 

capabilities of the M6 accelerometer. SD 

operation uses both forward and reverse 

piezoelectric effect to simultaneously 

measure acceleration and detect soft/hard 

failures. Both acceleration and diagnostic 

data are collected in real-time. 

Traditionally, an accelerometer’s low 

frequency band is reserved for 

acceleration measurements. To facilitate 

real-time detection, the SD system uses 

a separate, higher frequency band. 

Diagnostic data from this frequency band 

is collected by means of the reverse 

piezoelectric effect. Empirical models 

correlating diagnostic signatures to soft 

and hard failures are employed to 

determine the operating condition of 

the accelerometer. SD functions are 

developed from these empirical models. 

The initial design criterion for the M6 SD 

system is to detect several types of soft 

failures including when the accelerometer 

becomes loose from the base mount and 

changes in temperature. 

 
NASA/TM—2001-211156 2

Previous studies (ref.1-6) have proposed 

several signal processing techniques for 

evaluation of diagnostic data. These 

techniques include means for identifying 

an acceptable diagnostic frequency band 

and analyzing narrow-band as well as 

broadband data. Speed and accuracy of 

diagnostics are major issues for this 

application. Since several diagnostic 

events can occur simultaneously, the 

capability of the SD system to separate 

and distinguish a complete diagnostic 

record is important. 

The M6 Self-Diagnostic Accelerometer 

System 

The M6 Self-Diagnostic (SD) 

Accelerometer System continuously 

monitors for problems. As shown in 

Figure 1, the M6 SD Accelerometer 

Control System separates acceleration and 

diagnostic data in-situ. The Diagnostic 

Generator provides an electrical signal to 

drive the M6 crystals. It also measures 

the resulting diagnostic signature and 

formats SD data to detect soft and hard 

failures. The Accelerometer Signal 

Processor collects the acceleration signal, 

removes the low frequency characteristics 

of the Diagnostic Generator’s electrical 

drive, and provides a buffered acceleration 

signal. The SD Control System furnishes 

a continuous stream of acceleration data 

with a 20 kHz bandwidth. This system 

provides digital diagnostic information 

with a periodicity based on a discrete 

cycle time. The diagnostic cycle time is 

primarily controlled by the signal 

processing algorithm employed. The 

initial goal of the M6 SD accelerometer 

system is to provide diagnostic 

information once a second. 

 

Developing the SD Functions 

A SD function is a mathematical template 

used to either compensate diagnostic 

signatures for environmental conditions, 

i.e. temperature, or identify soft/hard 

failures. The frequency band of a SD 

function includes the primary resonance 

of the piezoelectric accelerometer, both 

mounted and free. A simple multi-port 

model of an accelerometer, as shown in 

figure 2, illustrates the inter-relationship 

among the accelerometer’s electrical, 

mechanical and piezoelectric properties 

when using both the forward and reverse 

piezoelectric effect. A SD function applies 

specific temporal and spectral characteristics of the reverse piezoelectric effect 

that relate a dynamic current source, I(s), 

to the sensor’s output voltage, ERl(s).

Figure 1: Schematic of the M6 Self-Diagnostic Accelerometer System.
NASA/TM—2001-211156 3

Figure 2; A compression-mode 

design accelerometer is shown 

with a simple multi-port model 

including input ports for both 

acceleration and a high-frequency 

current source. Mechanical 

components considered in this 

model include base and sensor 

housing impedance, Zb, sensor 

assembly impedance, Za, seismic 

mass, Ms, and piezoelectric 

crystal stiffness, Kp. The electrical 

components include piezoelectric 

capacitance, Cp and insulation 

load resistance, Rl . The 

sensitivity of the accelerometer is 

the ratio of output voltage across 

the load resistance to input 

acceleration. The SD frequency 

response relates dynamic current 

to output voltage across the load 

resistance.

Transfer Function of Forward Piezoelectric Effect 

 Transfer Function of Reverse Piezoelectric Effect 

where: 

A(s) = acceleration signal 

Cp = piezoelectric capacitance 

ERl(s) = voltage output 

I(s) = dynamic current source 

Kp = piezoelectric crystal stiffness 

Ms = seismic mass 

Np = piezoelectric sensitivity 

Rl = load resistance 

s = Laplace transform 

Za = assembly impedance 

Zb = base impedance

A1 = (Za+Zb) Ms Np2

 Rl Cp 

A2 = (Zb Za Np2

 Rl Cp + Ms Za Np2 + Ms Np2 Zb + Ms Rl + Ms Kp Np2 Rl Cp) 

A3 = (Zb Za Np2 + Zb Rl + Zb Kp Np2

 Rl Cp +Ms Kp Np2) 

A4 = Zb Kp Np2

 ] A 3 A 4

2 A 23

1 [A

 ( Ms Kp ZaZb) Zb Kp] )( 2 Rl[Ms(Za Zb) 2 Np

Rl )(

+++

++++ =

sss

sss

s

I E

 ] 2 Rl Cp Rl ) Kp Na 2 Kp Np 2 (Za Np 2 ) 2 Rl Cp Ms Np 2 (Za Np 3 Rl Cp) 2 [(Ms Np

 [(Np Rl Ms) )( ] 

Rl )(

++++++

=

sss

ss

s

A E
NASA/TM—2001-211156 4

The two transfer functions show the 

connection between forward and reverse 

piezoelectric effect. The transfer function 

for the forward piezoelectric effect relates 

dynamic acceleration, A(s), to output 

sensor voltage, ERl(s). In this case, the 

current source, I(s), approaches zero 

within this low frequency measurement 

band. Only the cyclic beat of the dynamic 

current source appears at a discrete low 

frequency and can be removed from the 

measured acceleration data. The transfer 

function for the reverse piezoelectric effect 

relates the dynamic current source, I(s), to 

output sensor voltage, ERl(s). Acceleration 

in the self-diagnostic frequency band may 

add noise to the measured voltage, ERl(s). 

If necessary, increasing the dynamic 

current source and/or further signal 

processing of SD data will reduce the 

affects of this type of uncorrelated noise. 

Due to potential unit-to-unit variations in 

the high frequency structural dynamics of 

the M6, an empirical analysis of a small 

group of accelerometers was used to 

develop the SD functions. The empirical 

analysis correlates specific diagnostic 

signatures to temperature and modes of 

failure. Figures 3-5 are graphic 

illustration from previous work of typical 

SD data related to specific soft failures. 

The M6 accelerometer is a shear-mode 

design. It is stud mounted to a base pad 

using 40 in-lb torque. In a voltage-mode 

operation, both the piezoelectric charge 

coefficient and capacitance will affect 

output sensitivity. The sensor’s 

fundamental “mounted” resonance is 

typically 40 kHz at room temperature. 

Initial testing of the M6 accelerometer 

identified other resonant frequencies both 

for mounted and free-free conditions. 

Results from impact testing and using 

the reverse piezoelectric effect show the 

correlation between the sensor’s resonance 

and the resonant/anti-resonant pairs of 

the SD spectral signature. A “free-free”

boundary condition for the M6 accelerometer represents sensor separation from 

the base with cable attachment. Placing 

the sensor on a foam pad simulates this 

condition. As shown in Figure 6, the 

“free-free” resonances of the M6 

accelerometer appear at 32, 57 and 

69 kHz. using both the forward and 

reverse piezoelectric effect.

 

 Figure 3: The SD 

signature of a 

compression-mode 

accelerometer as a 

function of mounting 

condition, i.e. loose, 

tight.. 

Figure 4: The SD 

signature of a 

compressionmode 

accelerometer as a 

function of 

ambient 

temperature.
NASA/TM—2001-211156 5 

Figure 5: The SD 

signature of a 

compression-mode 

accelerometer as a 

function of structural 

damage. 

The location of the mounted and “freefree” resonance are sufficiently different to 

initially focus on the 30-100 kHz range for 

SD function analysis and formulation. 

Differentiating the affects of temperature, 

mounting torque levels, and changes in 

base impedance, while minimizing the 

cross-sensitivity of the SD function/failure 

detection algorithm, is the goal of the test 

program. The SD function test program 

includes characterizing the diagnostic 

signatures produced by the M6 

accelerometer due to changes in mounting 

torque, base impedance and temperature. 

Figure 6: Impact testing of the M6 

accelerometer using a “free-free” boundary 

condition produces a frequency response 

identifying the sensor’s resonant 

frequencies. The resonant/anti-resonant 

pairs of the M6 accelerometer are also 

shown and correlate to accelerometer 

resonance.

 

SD Function Test Program 

A computer-aided test system employed in 

earlier studies (ref. 1-6) was used to 

measure M6 diagnostic signatures. This 

system uses a two-channel digital signal 

analyzer to calculate the frequency 

response between input electrical drive 

and output voltage across a fixed load 

capacitance. Data from the frequency 

response function is processed and 

correlated to soft and hard failures. 

Potential SD functions are developed from 

these test results. 

In the second phase, algorithms for the SD 

functions are downloaded to a prototype 

Self-Diagnostic M6 Accelerometer System 

and tested. The prototype Self-Diagnostic 

M6 Accelerometer System has a 

programmable frequency band using a 

periodic chirp drive and calculates, in-situ, 

diagnostic conditions. The dynamic 

current source includes automatic gain 

control in addition to software control of 

both bandwidth and resolution of the SD 

test frequencies. 

The prototype M6 accelerometer system 

hardware includes a “T” connector box 

interfaced to a data acquisition and 

control unit. The M6 accelerometer is 

connected to the “T” box using a low noise, 

low capacitance coaxial cable. A BNC 

signal jack can be used to monitor output 

acceleration and the unprocessed SD 

signature. The data acquisition and 

control unit measures and collects the SD 

signatures from the “T” box. A five-line 

Frequency R espo nse and SD Function of M 6 Accelerom eter

0

1

2

3

4

5

6

7

8

9

1 0

30000 40000 50000 60000 70000 80000

Frequency in Hz.

Amplitude

SD Function

M 6 Accelerometer
NASA/TM—2001-211156 6

LCD display allows “real-time” viewing of 

information concerning M6 operation. 

Diagnostic data is transferable to a 

computer using a serial port. Program 

modification and upgrading are also 

permitted using a second serial port. 

Tests conducted with the prototype unit 

helped verify the operation of the SD 

functions 

Identifying SD Functions 

Affects of Base Impedance on the M6 

Accelerometer

As predicted by the reverse piezoelectric 

effect transfer function, base mounting 

impedance will change the number and 

location of the resonant/anti-resonant 

pairs. Figure 7 illustrates the change in 

SD signature due to the shape and 

material properties of the mounting 

block. The dynamic range of the 

resonant/anti-resonant pairs can also 

fluctuate because of the constructive 

or destructive influence of the base 

eigenvalues on the SD signature. The 

“loose” SD signatures for each base 

condition are similar approaching the 

signature for the “free-free” boundary 

condition. The complexity of the SD 

signature increases above 70 kHz. At 

least one discrete resonant/antiresonant pair exists between 37 and 65 

kHz for all three base impedances. 

Figure 7: Affects of base impedance on SD 

data. SD data of the “loose” M6 is common 

to all three base impedances

Affects of Mounting Torque on the M6 

Accelerometer

Changing mounting torques from 25 to 

40 in-lbs measurably shifts the spectral 

resonance of the diagnostic signature. As 

illustrated in Figure 8, a resonant/antiresonant pair can shift as much as 1000 Hz 

as mounting torque increases. This 

magnitude of frequency shift is not 

observed for all resonant/anti-resonant 

pairs and can be affected by the base 

impedance. However, for the three base 

impedances tested, as mounting torque 

increases, the resonant/anti-resonant pairs 

continue to shift to higher frequencies until 

the M6 is properly mounted. Once the M6 

is loose (but still threaded to the base), the 

mounted SD signature shifts dramatically 

as illustrated in Figure 7. 

Based on repeatability tests, a 5 in-lb 

mounting torque resolution can be 

measured using SD data. Further results 

show that the resolution of the torque 

measurement using the spectral shift of 

the SD signature usually degrades at 

frequencies above 70 kHz. Minor changes in 

base mounting impedance including adding 

a washer can significantly change the SD 

signature. For example, a washer between 

the M6 and base impedance shifts the 

resonant/anti-resonant pairs to lower 

frequencies and changes the dynamic range 

of the resonant/anti-resonant pairs. 

Figure 8: SD data of the M6 accelerometer 

mounted to base impedance 2 using 25, 30, 

35 and 40 in-lb torque levels.

SD Frequency Resp onse

-29

-2 8 .5

-28

-2 7 .5

-27

-2 6 .5

-26

-2 5 .5

-25

30000 40000 50000 60000 70000 80000 90000 100000

Frequency in Hz .

Magnitude

Loose

B ase Im pedance 1

B ase Im pedance 2

B ase Im pedance 3

SD Frequency Response Mounted to Base Impedance 2

-30

-29

-28

-27

-26

-25

38000 38500 39000 39500 40000 40500 41000

Frequency in Hz.

Magnitude

25 in-lbs

30 in-lbs

35 in-lbs

40 in-lbs
NASA/TM—2001-211156 7

Affects of Temperature on the M6 Accelerometer

To help simulate the temperature 

conditions of the shuttle pumps in 

operation, both liquid nitrogen and an 

environmental control chamber are used. 

Cold temperature testing involves 

quenching the sensor in a liquid nitrogen 

bath. The SD spectral signature is 

measured as the M6 cools. After the SD 

signature stabilizes, the M6 is removed 

from the liquid nitrogen bath and 

diagnostic signatures are recorded until the 

M6 reaches room temperature. No 

temperature sensor is mounted to the M6 

since this will load the sensor’s housing 

thereby affecting the assembly impedance 

and diagnostic signatures. As shown in 

Figure 9, the bias level of the SD signature 

and the location of the resonant/antiresonant pairs continuously shift as the M6 

accelerometer warms from cryogenic to 

room temperature. Condensation in the 

form of frost developed on the sensor. This 

event did not appear to significantly affect 

the bias level data but, in some cases, 

damped the resonant/anti-resonant pairs. 

Little change in the damping characteristics 

of the resonant/anti-resonant pairs was 

recorded for the “loose” M6 when exposed 

to this event. The bias level, and spectral 

location and shape of the resonant/antiresonant pairs for the diagnostic signature 

returns to the original state once ambient 

conditions are restored. 

High temperature testing involved placing 

the M6 with mounting base inside a 

Despatch environmental chamber. A 

controlled temperature ranging from 23 oC 

(73 oF) to 90 oC (194 oF) was maintained 

during this study. The high temperature 

diagnostic signatures, in Figure 10, also 

show a shift in resonance frequency and 

bias with temperature. The resonant 

frequencies shift with increasing 

temperature in the same direction as the 

low temperature test, while the bias shifts 

in the opposite direction. Monitoring 

temperature requires tracking both the SD 

signature bias level and the location of the 

resonant/anti-resonant pairs. 

Figure 9: SD data of the mounted (base 

impedance 3) M6 accelerometer as it warms 

from cryogenic to room temperature. The 

arrow shows direction of SD signature bias 

level as the M6 warms.

Affects of the Electrical Drive Signal on the M6 

Accelerometer

The M6 accelerometer was tested to 

determine the changes in SD signature 

due to a 20 dB change in electrical drive 

level. This study measures the affect of 

automatic gain control for the electrical 

drive. A minute difference in the SD 

function due to the 20 dB increase occurs 

at the resonant/anti-resonant pairs. Long 

term test results comparing different drive 

levels within the 20 dB range show no 

significant change that would affect the 

development of the SD functions. 

Figure 10: SD data of the mounted (base 

impedance 2) M6 accelerometer at 

elevated temperatures. The angled arrow 

shows direction of SD signature bias 

level and frequency shift due to 

increased temperature from 23 to 90 C. 

SD D ata as M 6 W arm s to Room T em perature

-20

-18

-16

-14

-12

-10

30000 40000 50000 60000 70000 80000 90000 100000

Frequency in Hz.

Magnitude

SD Data at Elevated Temperatures

-13

-12

-11

-10

-9

30000 40000 50000 60000 70000 80000 90000 100000

Frequency in Hz

Magnitude
NASA/TM—2001-211156 8 

SD Functions and the Prototype System 

Three SD functions are proposed to 

identify and/or measure (1) a “loose” M6 

mounting condition (2) a correctly 

mounted M6 accelerometer and (3) 

environmental temperature. Since base 

mounting impedance can alter the location 

and dynamic range of the resonant/antiresonant pairs, a self-calibration for the 

mounted M6 is required for each new 

base. The “loose” SD signature is not 

affected by the base impedance and 

therefore is a standardized signature for 

each M6 accelerometer. A test of the 

“loose” M6 SD signature checks the piezoelectro-mechanical properties before 

torque-down. The “loose” SD function for 

each M6 is archived in the SD system. 

The SD signature for the correctly 

mounted M6 is recorded immediately after 

installation. A broadband sweep of the 

diagnostic frequency band identifies the 

location and dynamic range of each 

resonant/anti-resonant pair for the 

mounted M6. The resonant/anti-resonant 

pair with the peak dynamic range centers 

the SD frequency band. The frequency 

range of the SD signature extends to 

include the primary “loose” resonant/ 

anti-resonant pair at 57 kHz. Potential 

variations in environmental temperature 

and sensitivity to mounting torque 

typically require further expansion of the 

frequency range by as much as 5000 Hz, 

adding 2500 Hz to the lower and high 

ends of the frequency range. Base 

impedance tests show that several discrete 

resonant/anti-resonant pairs for the 

mounted M6 appear in the 35 to 65 kHz 

range. All are good candidates for 

diagnostic detection. This band 

also includes the “loose” resonant/antiresonant pair at 57 kHz. A step-by-step 

process for installing the M6 using the 

SD system is shown in Figure 11. 

The installation process for the M6 

accelerometer begins by measuring, insitu, the “loose” SD signature. This is a 

broadband SD signatures exciting the 30 

to 80 kHz frequency range. Measured SD 

data is analyzed to determine bias level 

and position of the resonant/anti-resonant 

frequencies. The acceptance criterion 

compares the measured bias level and 

resonant/anti-resonant frequencies to the 

SD function data for the “loose” M6 mount 

condition. If acceptable, the temperature 

data is recorded and SD function 

sensitivity to torque level is checked next. 

The torque sensitivity test requires 

remounting the M6 using several different 

torque levels. A broadband, high 

resolution SD signature is recorded for 

each torque setting. This test identifies 

frequency band sensitivity to changing 

torque levels. The torque sensitive 

frequency range is included in the 

operational SD frequency band. Following 

this test, the M6 is properly mounted to 

the base pad. The broadband, highresolution SD signature is again measured 

and temperature level is calculated using 

the SD temperature function. This 

temperature reading is compared to the 

“loose” mount temperature measurement 

as a check. The operational or “tuned” SD 

frequency band is set based on specific 

data including the torque sensitivity 

test results, the dynamic range of the 

resonant/anti-resonant peaks and the 

“loose” SD signature. Comparing 

temperature calculations using both 

broadband and tuned SD signatures 

confirms the operation of the SD 

temperature function using a narrow 

tuned SD frequency band. If calculated 

temperature of tuned SD frequency band 

differs significantly from the broadband 

measurement, the tuned SD frequency 

band is expanded and retested. 

Incremental expansion continues until the 

temperature reading agrees or reaches the 

broadband SD frequency band. The 

frequency band is kept as small as 

possible to minimize diagnostic cycle time. 

At this time, the prototype system has 

been programmed to test to following: 

1) Operation of the broadband, high 

resolution SD signature to detect 

resonant/anti-resonant peaks of the 

mounted and loose M6 accelerometer. 
NASA/TM—2001-211156 9

Figure 11: Flow chart of SD system procedure for installing M6 accelerometer.

 

Acceptable 

“Loose” SD 

Signature? 

FAILED

Start 

M6 Installation

Thread M6 to Base 

Mount: Loose 

Condition 

Measure Broadband SD 

Signature

Remove 

M6 & 

Check 

Operation 

Record 

Temperature

Mount M6 to 

Base Pad using 

Different Torque 

Level 

Measure Broadband SD 

Signature

Record 

Temperature

Acceptable 

Temperature 

Comparison? 

Set Frequency 

Band for SD 

Signature 

Measure Tuned SD 

Signature

Record 

Temperature

Acceptable 

Temperature 

Comparison? 

yes 

yes 

no 

no 

Expand 

Frequency 

Band? 

no 

yes 

yes 

no Display & 

Record New 

Temperature 

Data

Accept 

New 

Data?

no 

yes 

Start Monitoring 

Issue Warnings for 

1) Loose Mounting 

2) Change in Torque 

Level 

3) Atypical SD 

Signature 

4) Hard Failures 

Record & Display 

Temperature

Measure Broadband SD 

Signature

Identify Frequency 

Range for Torque 

Level Detection 

Mount M6 to 

Base Pad using 

Proper Torque 

Level 
NASA/TM—2001-211156 10 

2) Procedure to set the tuned 

frequency range for the SD 

signature. 

3) Performance of the operational 

SD signature to detect “loose” and 

“mounted” conditions 

4) Performance of the SD 

temperature function versus 

temperature. 

5) Performance of the hard failure 

detection mode when the 

termination impedance of the 

sensor abruptly changes to either 

an open or short circuit condition. 

 

All four functions have been successfully 

tested using an estimated one-second 

diagnostic cycle time. Additional software 

procedures outlined in Figure 11 are being 

added to the SD system. 

Conclusions 

This paper discusses the general operation 

of the M6 accelerometer SD system and 

procedures for developing and evaluating 

the SD system. Results show that 

analyzing the high frequency spectral 

characteristics of the M6 accelerometer’s 

reverse piezoelectric effect can 

significantly enhance the diagnostic 

capabilities of the sensor. Specific hard 

and soft failures exhibit unique signatures 

that can be detected using mathematical 

(SD) functions while compensating for 

environmental temperature. This highspeed self-diagnostic sensor is especially 

important in complex propulsion systems. 

References 

1) Atherton, W. J. and Flanagan, P. M., 

" A Self Diagnostic System for 

Piezoelectric Sensors ", AIAA paper 

no. 89-2638, 

AIAA/ASME/SAE/ASEE 25th Joint 

Propulsion Conference, Monterey, 

Ca., July 10-12, 1989 

2) Flanagan, P. M and Atherton, W. J., 

"Developing a Self-Diagnostic 

System for Piezoelectric Sensors", 

AIAA paper no. 90-2230, 

AIAA/ASME/SAE/ASEE 26th Joint 

Propulsion Conference, Orlando, Fl., 

July 16-18, 1990 

3) Flanagan, P. M, "In-Situ 

Measurement of Sensitivity for a 

Piezoelectric Sensor", AIAA paper 

no. 91-2521, 

AIAA/ASME/SAE/ASEE 27th Joint 

Propulsion Conference, Sacramento, 

Ca., June 24-26, 1991 

4) Flanagan, P. M, "Design of a SelfDiagnostic Beam-Mode Piezoelectric 

Accelerometer", AIAA paper no. 92-

3656, AIAA/ASME/SAE/ASEE 28th 

Joint Propulsion Conference, 

Nashville, Tenn., July 6-8, 1992 

5) Flanagan, P. M, "Dedicated System 

for a Self-Diagnostic Piezoelectric 

Accelerometer", AIAA paper no. 94-

2982, AIAA/ASME/SAE/ASEE 30th 

Joint Propulsion Conference, 

Indianapolis, In., June 27-29, 1994 

6) Flanagan, P. M, "Design of a SelfCompensation System for Piezoelectric 

Accelerometers", AIAA paper no. 96-

2935, AIAA/ASME/SAE/ASEE 32th 

Joint Propulsion Conference, Lake 

Buena Vista, Fl., July 1-3, 1996
This publication is available from the NASA Center for AeroSpace Information, 301–621–0390.

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NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

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298-102

Form Approved

OMB No. 0704-0188

12b. DISTRIBUTION CODE

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Unclassified Unclassified

Technical Memorandum

Unclassified

National Aeronautics and Space Administration

John H. Glenn Research Center at Lewis Field

Cleveland, Ohio 44135–3191

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National Aeronautics and Space Administration

Washington, DC 20546–0001

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

November 2001

NASA TM—2001-211156

AIAA–2001–3318

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WU–704–30–53–00

16

A Self-Diagnostic System for the M6 Accelerometer

Patrick M. Flanagan and John Lekki

Sensor; Smart accelerometer; Piezoelectric

Unclassified -Unlimited

Subject Categories: 19 and 06 Distribution: Nonstandard

Prepared for the 37th Joint Propulsion Conference and Exhibit cosponsored by the AIAA, SAE, AIChE, and ASME,

Salt Lake City, Utah, July 8–11, 2001. Patrick M. Flanagan, Fenn College of Engineering, Cleveland State University,

1983 E. 24th Street, Cleveland, Ohio 44115–2403; and John Lekki, NASA Glenn Research Center. Responsible person,

John Lekki, organization code 5520, 216–433–5650.

The design of a Self-Diagnostic (SD) accelerometer system for the Space Shuttle Main Engine is presented. This retrofit

system connects diagnostic electronic hardware and software to the current M6 accelerometer system. This paper

discusses the general operation of the M6 accelerometer SD system and procedures for developing and evaluating the

SD system. Signal processing techniques using M6 accelerometer diagnostic data are explained. Test results include

diagnostic data responding to changing ambient temperature, mounting torque and base mounting impedance.