An automatic radiated susceptibility test system (ARSTS) was developed for NASA Lewis Research Center's Electro-magnetic Interference laboratory. According to MSFC-SPEC 521B, any electrical or electronic equipment that will be transported by the spacelab and space shuttle must be tested for susceptibility to electromagnetic interference. This state-of-the-art automatic test system performs necessary calculations; analyzes, processes, and records a great quantity of measured data; and monitors the equipment being tested in real-time and with minimal user intervention. ARSTS reduces costly test time, increases test accuracy, and provides reliable test results

Ngo, Hoai T.

Sargent, Noel B.

Sturman, John C.

English

NASA Technical Reports Server

NASA-TM-107059
NASA Technical Memorandum 107059 [_ (0000"](DOG-I
AIAA-95-3656
a
Automatic Radiated SusceptibilityTest
System for Payload Equipment
Hoai T. Ngo
Lewis Research Center
Cleveland, Ohio
John C. Sturman
Analex Corporation
Brook Park, Ohio
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Prepared for the ............
1995 Space Programs and TechnologiesConference
sponsored by the American Institute of Aeronautics and Astronautics
Huntsville, Alabama, September 26-28, 1995
/
NationalAeronauticsand
SpaceAdministration
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AUTOMATIC RADIATEDSUSCEPTIBILITYTEST SYSTEM
FOR PAYLOAD EQUIPMENT
Hoai T. Ngo
National Aeronautics and SpaceAdministration
Lewis Research Center
Cleveland, OH 44135
John C. Sturman
Analex Corporation
Brook Park, OH 44142
Noel B. Sargent
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, OH 44135
Abstract test frequency, field sensor readings, and instrument
status. It also enables the test engineer to display and
An automatic radiated susceptibility test system print all test setup parameters, test results, and docu-
(ARSTS) was developed for NASA Lewis Research mentation.
Center's Electromagnetic Interference laboratory. Ac-
cording to MSFC-SPEC 521B, any electrical or elec- For the tests required by MSFC-SPEC521B, which
tronicequipment that will be transportedby the spacelab covers the frequency range of 14 kHz to 18 GHz, the
and space shuttle must be tested for susceptibility field strength must be measured at 1422 frequencies in
to electromagnetic interference. This state-of-the-art 1-percent increments. The amount of time at each fre-
automatic test system performs necessary calculations; quencydepends on the EUT. If the dwell time is 20 sec
analyzes, processes, and records a great quantity of at each frequency,the test will take over8 hr, not includ-
measureddata; and monitors the equipment being tested hagthe timefor setup, data acquisitioncycle, processing,
in real-time and with minimal user intervention. ARSTS and display.If failuresoccur, the test time becomes even
reduces costly test time, increases test accuracy, and longer.Automaticallycontrolling the processesof setting
provides reliable test results, frequencies,tuning signalgeneratorknobs, and adjusting
amplifier power can reduce test time.
Introduction
Overall View
Radiated susceptibility testing determines the sus-
ceptibility of shuttle payload equipment to radiated The ARSTSsoftwareautomaticallyexecutes the test
electromagneticfields. This test, which is typically done procedureand data recording. Thisautomaticprocesscan
by the engineer monitoring the equipment, requires a be broken into the following steps:
pass/fall condition to be determined at each electromag-
netic frequency over a wide test range. The resulting • Dataacquisition
large amount of data is difficult to analyze and mani- • Test instrumentation selection
pulate during testing and even after. The automatic test • Automaticradiated susceptibilityprocess
system resolves these difficulties by controlling radio- • User involvement
frequency (RF) equipment, monitoring the equipment
being tested, and collecting data. Depending on the Data Acquisition
. equipment's position in the orbiter payloadbay, ARSTS
canenable the test engineer to readily select a field level ARSTSusespower amplifiers,frequencygenerators,
or to make modifications for a particular application transmittingantennas,modulators,RF switches,and field
f (such as changing the field intensity to be applied to the sensors thatare connected by fiber-optic cables to a field
equipment under test (EUT) if a susceptibility is detec- meter. The computer controls the interface with the
ted). With this software, the test engineer can view RF equipment and instrumentation via a general pur-
informationin real time--including process time, current pose interfacebus (GPIB), as illustrated in Fig. 1. This
This paper is declared a work of the U.S. Government and is not sub-
ject to copyright protection inthe United States.
1
American Institute of Aeronautics and Astronautics
ARSTSprogram
Shieldedroomwall
1o_. 16GHZ|
-- 14_ •1GHZ
Figure 1.--Automatic system integration. Figure 3.--Susceptibility test monitoring.
software enables ARSTS to operate the instruments and Test Instrumentation Selection
to completely control hardware interfaces. ARSTS pro-
vides closed-loop, computer-controlled leveling of the Several things must be considered when choosing
field intensity by comparing the output of the radiating the right test instruments to include in the automatic test
system with the radiated level measured by the field system:
sensor in the shield room.
(1) The system's architecture must be designed
The software is divided into three subsystems: with connecting instrumentation to reduce instrumenta-
tion costs and software development time. For example,
(I) Display--The display subsystem sets the setup instead of controlling just one amplifier, an RF actuator
parameters of a susceptibility test, including the test relay could control a number of amplifiers.
instrument configuration (Fig. 2).
(2) The equipment must be able to operate under the
(2) Critical test information--During the tests, this conditions required by the test, such as particular field
subsystem automatically levels and controls the RF field levels and frequency ranges.
in real time (Fig. 3).
(3) Instruments should come with a standardized,
(3) Data--The data subsystem enables the test controllable GPIB.
engineer to display and print all test results and docu-
mentation after a test is complete. (4) Instruments must be accurate and stable, control-
ling most functions needed to perform the test.
ARSTSprogram
Automatic Radiated Susceptibility Process
A closed-loop, automatically controlled, susceptibil-
ity process includes several steps (Fig. 4):
(1) The system initializes the hardware by issuing an
"off' command to the RF output of the signal generator,
then setting a low initial RF level to avoid overstressing
the EUT.
!
(2) Once the test setup has been corrected, the test
engineer switches the system to auto mode.
(3) Then, the system decreases or increases the RF
Figure 2.-- Test setup screen, level of the signal generator from the equation:
2
American Instituteof Aeronautics and Astronautics
Fieldmmur_ or can turn off the RF generator--this automatically
RF w = RFola - 201og Fieldd_ switchesthe system to manual mode. If the RF signal is
turned off, it must be turned back on before the system
can be switched to auto mode again.
The new RF level increases if the measured field
is less than the desired field, and it decreases if the User Involvement
measured field is greater than the desired field. The
process continuesuntil the measuredfield approachesthe WhileoperatingARSTS, the testengineermust enter
desired field. At this point, the system automatically choices from the menus and input answers to questions
records the frequency, RF signal level, and threshold about the EUT.In addition, this engineer usually investi-
level. Then, it continues with the test procedure by step- gates the test setup and sets test parameterssuch as fre-
ping-up to the next frequencyusing a step size predefined quency range, step size, requiredtest level, dwell time,
by the test engineeror anotherperson responsible for the and instrument settings.
EUT. The test engineer can measure the EUT's per-
formance throughout its exposure to the electromagnetic Before starting the test, the test engineer places the
field.When a failureoccurs, the test engineer determines EUT and field sensors inside the shielded enclosure and
the susceptible threshold level manually by using the up positionsthe antennas 1m from the EUT. When the soft-
and down arrowkeys on the computer to reduce the RF ware indicates that the antenna needs to be changed,
signal level until the malfunction or degradation corn- the engineer manually changes the antenna (the three
pletely disappears. The system then records the fre- antennasusedrespond to different frequencyranges). At
quency, RF signal level, and threshold level, as well as a this point, the software automatically disables the RF
description of the failure, output to prevent any damage to the EUT and to pro-
tect personnel from RF exposure. After the antenna is
ARSTS canbe used in twointerchangeablemodes-- changed, testing can resume.
auto and manual.During the auto mode, the test engineer
can pause the system by switching it to manual mode To make necessary interventions, the test engineer
must observe the EUT while it is exposed to the field.
This canbe done by watching the monitor as it displays
[ ,,_a_,o ] images grabbedand stored by the internal software or by
° anothermethod of observing the test sample.
t" ConcludingRemarks
The automatic radiated susceptibility test system
(ARSTS)benefits electromagnetic interference suscepti-
bility testing of complex space experimentsby quickly
obtaining,recording, nd processing the arge amount of
N[_ data required by MSFC-SPEC-521B. After the test is
complete, the test engineer selects a menu option to
obtain document-ready test results, including a descrip-
tion of the test items, project rifles,operator name, date
_,!_: _--_ st_,o_,, I and time, frequency ranges determined by antenna type,
I _ ] pass or fail marks, and tabulated test results. All results
can be saved to disks for future reference.
No
Next Frequenc_ I
__ NASA Lewis is currently adding a 32- by 24- by
_o 16-ftshieldedenclosure to accommodatelarger payloads
' and a 16- by 10- by 8-ft shielded enclosure to isolate
ground support equipment and instrumentation from the
Yes / ElectromagneticInterference laboratory facility.ARSTS
J _ and the new test area will increaseNASA Lewis' ability
to conduct tests according to military and commercial
Figure 4._Automatic process for determining specifications.
susceptibility.
American Institute of Aeronautics andAstronautics
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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
September 1995 Technical Memorandum
4. "ITrLE AND SUBTITLE 5. FUNDING NUMBERS
\
AutomaticRadiated Susceptibility Test System for Payload Equipment
6. AUTHOR(S) WU-963-80-0D
HoaiT. Ngo, John C. Sturman, and Noel B. Sargent
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
REPORT NUMBER
National Aeronautics andSpace Administration
Lewis Research Center E-9914
Cleveland, Ohio 44135-3191
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
National Aeronautics and Space Administration
Washington,D.C. 20546-0001 NASATM-107059
AIAA-95-3656
11. SUPPLEMENTARY NOTES
Preparedforthe1995SpaceProgramsandTechnologiesConferencesponsoredby theAmericanInstituteof AeronauticsandAstronau-
ties, Huntsville,Alabama,Septgmber26-28, 1995.HoaiT. NgoandNoelB. Sargent,NASALewisResearchCenter;JohnC.Sturman,
AnalexCorporation,3001AerospaceParkway,BrookPark,Ohio44142(workfundedbyNASAContractNAS3-25776).Responsible
person,HoaiT.Ngo,organizationcode4130,(216)433-2533.
12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE
Unclassified -Unlimited
Subject Categories 05, 14, 18, and 33
This publicationis available from the NASA Center for Aerospace Information, (301) 621-0390.
13. ABSTRACT(Maximum 200 words)
An automaticradiatedsusceptibility test system(ARSTS)was developed forNASALewis ResearchCenter'sElectro-
magneticInterferencelaboratory.According to MSFC-SPEC521B, any electricalor electronicequipment thatwill be
transportedby thespacelab and space shuttlemust be testedfor susceptibilityto electromagneticinterference.Thisstate-
of-the-art automatictest system performsnecessarycalculations;analyzes,processes,and recordsa greatquantityof
measureddata;and monitorsthe equipmentbeing testedin real-timeand with minimaluserintervention.ARSTSreduces
cosily test time, increasestest accuracy,and providesreliabletest results.
14. SUBJECTTERMS 15. NUMBER OF PAGES
5
Electromagnetic interference testing 16.PRICECODE
A02
17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITYCLASSIFICATION 20. LIMITATION OF ABSTRACT
OF REPORT OF THIS PAGE OF ABSTRACT
Unclassified Unclassified Unclassified
NSN 7540-O1-280-5500 Standard Form 298 (Rev. 2-89)
Presc_ribed by ANSI Std. Z39-18
298-102


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