NBSIR 74-379

COMPLETION OF THE PROGRAM TO EVALUATE / IMPROVE

INSTRUMENTATION AND TEST METHODS FOR

ELECTROEXPLOSIVE DEVICE SAFETY QUALIFICATION

Hudson, Paul A. Melquist, Dean G.

Ondrejka, Arthur R.

Werner, Paul E.

Electromagnetics Division

Institute for Basic Standards

National Bureau of Standards

Boulder, Colorado 80302

Final Report

June 1974

Prepared for

DEPARTMENT OF THE AIR FORCE

Aeronautical Systems Division (AFSC)

Wright-Patterson Air Force Base, Ohio 45433
I:
NBSIR 74-379

COMPLETION OF THE PROGRAM TO EVALUATE / IMPROVE

INSTRUMENTATION AND TEST METHODS FOR

ELECTROEXPLOSIVE DEVICE SAFETY QUALIFICATION

Hudson, Paul A. Melquist, Dean G.

Ondrejka, Arthur R. Werner, Paul E.

Electromagnetics Division

Institute for Basic Standards

National Bureau of Standards

Boulder, Colorado 80302

Final Report

June 1974

Prepared for

DEPARTMENT OF THE AIR FORCE

Aeronautical Systems Division (AFSC)

Wright-Patterson Air Force Base, Ohio 45433

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS R. chard W Roberts Director

FOREWORD

This program was initiated at the National Bureau of

Standards in response to a request from the Aeronautical

Systems Division (AFSC) of the Air Force, Wright-Patterson AFB.

Funding for the effort was provided by the Air Force (Contract

No. F 33515-72-5013) . The general objective was to provide

the Air Force with optimum test procedures, instrumentation,

and test devices for qualification of weapon systems with

respect to electroexplosive device (EED) safety.

Phases I and II of this project were concerned with

evaluation of existing test instrumentation and the development

of a new go, no-go device to fill a test instrumentation need.

These have been described in the NBS Report NBSIR 73-323.

Phase III, the subject of this report, is the conclusion of

the project. During this phase, instrumentation was developed

to provide the Air Force with a means for obtaining quantitative measurements of the stray rf power within a weapon.

The instrumentation to be described uses solid-state diode

detectors to measure both pin-to-pin power and pin-to-case

rf voltages. Both of the measured quantities are plotted on

a strip chart recorder.

iii
r CONTENTS

Page

1. INTROnCJCTION 1

2. THE VIDEED SYSTEM 2

3. VIDEED 3

4. CARBON-TEFLON CABLE 6

5. CABLE ADAPTER 8

6 . INSTRUMENTATION AMPLIFIERS 9

7. RECORDERS 11

8. TESTIKC, THE VIDEED SYSTEM 11

8.1. DC Testing 11

8.2. RF Sensitivity Testing 12

8.3. RF Impedance....' 15

9. CONCLUSION 15

10. ELECTRICAL AND MECHANICAL SPECIFICATION

SUMJ^IARY . 15

iv
LIST OF FIGURES

Page

1. VIDEED system 19

2. VIDEED

a. p-c side

b. p-p side 20

3. Interface amplifier circuit 21

4. Saturation indicator circuit 22

5. Cable and amplifier test unit 23

6. VIDEED test unit 24

7. RF test setup (p-p) 25

8. VIDEED output vs frequency

(0° between input leads) 26

9. VIDEED output vs frequency

(180° between input leads) 27

10. VIDEED output vs power input

(180° between input leads) 28

11. VIDEED output vs input power

(0° between input leads) 29

12. Mechanical details of VIDEED 30

V
ABSTRACT

Qualification of weapon and missile systems for electroexplosive device (EED) safety has been a continuing problem

in the military services. Quantitative measurement of

stray energy in EED ' s has been hampered by limitations of

existing sensors. This report describes a new video diode

detector instrumented EED (VIDEED) which responds to both the

normal pin-to-pin energy (which would heat an EED bridgewire)

and to the pin-to-case voltage (which might cause EED ignition

due to arcing)

.

Also described in this report are the amplifiers,

cables, adapters and recorders which make up the rest of

the measuring system. Mention is also made of the test

procedures used in testing the VIDEED system.

Key words: Electroexplosive device safety; electromagnetic

compatibility; electromagnetic interference; stray energy

sensor.

vi
COMPLETION OF THE PROGRAM TO EVALUATE/ IMP ROVE

INSTRUMENTATION AND TEST METHODS FOR ELECTROEXPLOSIVE

DEVICE SAFETY QUALIFICATION

1. INTRODUCTION

Military testing of weapons for Electroexplosive Device

(EED) safety has depended for a number of years on two types

of test monitors. One was a type of EED which ejected a

piston when the explosive was actuated. Extension of this

piston indicated that the currents on the firing cable exceeded

that required to detonate the device but gave no indication

of the magnitude of the current. There was no way to determine

by how much the firing current was exceeded or how often prior

to firing the critical current was approached. The second

device was an EED in which the explosive charge was replaced

by a thermocouple temperature sensor. In this device, the

heat from the bridgewire was continuously monitored to determine if it exceeded the firing point of the removed explosive.

The thermocouple device provided a quantitative indication of

currents in the firing circuits (pin-to-pin) but offered no

indication of the pin-to-case voltages which might also

initiate the EED due to arcing or dielectric heating of the

charge

.

The video diode detector instrumented EED (VIDEED)

described in this report monitors hazardous rf signals in both

the pin-to-pin and pin-to-case configurations. It is useful

from below 1 GHz to 9 GHz, has a pin-to-pin sensitivity of

better than 0.5 volt per watt and a pin-to-case sensitivity

better than 7 millivolts per milliwatt of absorbed power. The

impedance was designed to be 2 ohms pin-to-pin and 500 ohms

from either pin to the case. During the testing phase of
the project a technique had to be developed to calibrate

the VIDEED in both the pin-to-case mode (simply a standard

unbalanced coaxial configuration) and the pin-to-pin mode,

which is a balanced transmission line. These are described

in the text along with the more usual "one pin grounded"

configuration.

2. THE VIDEED SYSTEM

Figure 1 shows the complete VIDEED system including

the VIDEED, cable adapter, carbon- impregnated teflon output

leads, interface amplifier and strip chart recorder.

The VIDEED was designed to replace the normal EED in

a weapon, measure the stray rf power on the firing wires and

make these measurements available to a remotely located

strip chart recorder.

The dc voltage generated by the VIDEED is transmitted

to the recorder on a cable composed of carbon-teflon

conductors. Because of the high losses in this cable, the

rf pickup is attenuated, reducing the measurement error that

might have been caused due to rf leakage into the weapon.

This cable also appears nearly transparent to rf fields so

that it can be located near the measurement site without

distorting the field environment.

The carbon-teflon cables suffer from the difficulties

normally associated with high-impedance circuits. They

are sensitive to static pickup, and noise is generated in

them when flexed. They will couple to 60 Hz signals, and

these will affect the detector circuits as well as the recorder.

To combat these difficulties, loading resistors were located

near the detector to shunt these voltages to ground. Since

2
these resistors were too large a value to make in a thin-film

structure, lumped constant resistors had to be used and were

mounted in a separate cable adapter unit. The addition was

successful in reducing the noise pickup to an acceptable amount.

The dc voltages produced by the diodes are recorded

by a dual channel strip chart recorder. One channel is used

to indicate the pin-to-pin (p-p) voltage, and the other

indicates the larger of the two possible pin-to-case (p-c)

voltages. Since the carbon-teflon cables have a high resistance

(.4 to 4 MQ, per channel), they cannot supply sufficient

current to drive most recorders directly, and an interface

amplifier is required. This amplifier has more than 40

megohm input impedance and an output impedance low enough to

drive the recorder inputs (above 3 00 ohms) . The "OR" gate

shown in figure 1 is actually an analog "OR" gate which

selects the higher of the two p-c signals. The recorder

can be any convenient two-channel strip chart recorder with

300 ohms or more input resistance and chart speeds about

1 mm per second. Each of these parts will be described in

greater detail.

3. VIDEED

The VIDEED shown in figure 1 is a small [7 mm (.275")

dia. X 15.875 mm (5/8") long] rf sensor designed to be

installed in a weapon system in place of the normal EED.

The two input leads extend out of the plastic* header and

can be connected to the normal firing circuit in the weapon.

The entire detector circuit is constructed on a small

ceramic substrate (6.35 mm X 6.35 mm X 0.254 mm). Figure 2a

shows the p-c side of the substrate, and figure 2b shows the

opposite side with the p-p circuitry on it. Four wire leads

*copolymer of polyethelyne and teflon chosen for rf

characteristics and mo].dability

3
are shown entering the plastic header and are fastened to

the substrate with conductive epoxy. The two outer leads

are grounds and are epoxied to the case as a final step in

the construction. After the contact to the case has been

established and tested these two leads are cut and not used

in actual practice. The dc outputs are brought out through

a specially designed plastic plug. All circuit components

are connected to the substrate circuit with conductive epoxy.

The diodes Dl and D2 (fig. 1) form half-wave rectifier

circuits and serve to measure the rf voltages between either

of the input leads and the case which can be grounded to the

weapon. Diodes D3 and D4 (fig. 1) form a bridge circuit with

their associated capacitors and detect voltages appearing

across the 2-ohm resistor.

The 2-ohm resistor is a thin metallic film deposited on

a ceramic substrate and takes the place of the EED bridgewire. The bridgewire in a normal EED is mounted between

the two input leads and causes the pin-to-pin input impedance

to vary quite severely over the frequency range of 1 GHz

to 10 GHz. Mention of the impedance measurement is

made later in this report, but, for the present, it is

sufficient to point out that the bridgewire will absorb rf

energy optimally when its impedance matches that of the rf

source. Without prior knowledge as to what the source

impedance might be in any given weapon, it was decided to try

to make a VIDEED with a low, constant rf impedance. This

would simplify the interpretation of the measured data in

that the impedance of the VIDEED would be more or less

constant

.

During the later months of the project, a need was

expressed for a VIDEED with a 500 ohms or higher impedance

pin-to-pin. It seems desirable in future work of this type
to use both a high and a low impedance VIDEED. In this way

it will be possible to estimate the Thevenin equivalent

circuit for the rf source impedance in the weapon. This

could lead to a more complete analysis of the EED rf problem.

EED firing in the pin-to-case mode is normally attributed

to arcing, and a measure of the pin-to-case open circuit

voltage would be useful in detecting the possibility of this

occurring. However, during the design phase of this circuit

it became apparent that the impedance of the diode and

capacitor would drop to about 500 ohms at 10 GHz instead of

the desired open circuit. Rather than allow the impedance

to vary from tens of kilohms at low frequencies down to

500 ohms at 10 GHz, a 500-ohm shunting resistor was deposited

onto the substrate. The combination impedance varied between

500 ohms at the low frequencies to about 250 ohms at 10 GHz.

This shunt resistance somewhat reduces the VIDEED sensitivity

to the high rf voltage which would be present before an arc

occurs, but still allows a meaningful measurement to be made.

The advantage of the circuit is the more nearly constant

impedance as the rf frequency increases.

In the pin-to-case mode no more than 7 milliwatts of

rf power is required to produce an output of 50 millivolts,

which is a minimum convenient readable signal. One watt

of input power will produce several volts of dc output.

In the pin-to-pin mode a similar 50 millivolt output

required an input net power of 90 milliwatts. This is, of

course, due to the low input impedance, but this low sensitivity was not entirely satisfactory for Air Force use. To

compensate for this difficulty, the interface amplifier gain

was increased from unity to ten. With this change it is easy

5
to resolve ten to fifteen milliwatts of power. Ninety

milliwatts of rf power now produces full-scale deflection

of the recorder (.5 volts).

More complete details of the calibration procedure

and results are given later in this report.

4 . CARBON-TEFLON CABLE

During a typical field safety test, the VIDEED is located

within a weapon structure, and the recording devices are

external. The telemetering device chosen was a carbon-loaded

teflon conductor which has a very high rf attenuation and is

transparent to rf fields. This type of teflon conductor has

been used at NBS for a number of years and has been proven

reliable. The conductive portion of the particular leads for

this project is made-up of .711 mm (0.028") diameter teflon

which has been loaded with a sufficient amount of carbon to

reduce its resistance to 66 kilohms per meter. A nylon jacket

.076 mm (0.003") thick protects the soft teflon from abrasion

and prevents shorting between adjacent wires in the cable.

The cable itself is made up of six teflon conductors held in

a bundle by a heat-shrinkable outer jacket.

Connectors having seven pins were used to interconnect

the cables. The six pins, arranged hexagonally, connect to

the six cable wires. The seventh pin (center) is jumpered

to ground at the connector and forms the interlock for the

instrumentation amplifiers.

Since the conductor is teflon, adhesives such as conductive

epoxy are not successful in making connection to the pins

of the plug. Instead, a slip fit was designed where the teflon wire was drilled coaxially about 6.35 mm into its end.

6
The hole provided a snug fit for the #28 copper wire inserted

into it. After the 6.35 mm long wires were soldered to the

connector pins the teflon wires could be slipped onto them,

making reliable contact. The connectors were filled with a

nonconductive epoxy, forming a good bond between the brass

connector and the nylon jackets on the teflon wires. The

cable was finished by heat shrinking a teflon sleeve over the

connector and cable.

Figure 1 shows the connection of the six cable wires.

The ground wire connects the VIDEED case (which may also

be the weapon ground) to the amplifier case ground. It

is effective grounding only for interference coming from

a very high impedance source, e.g., static pickup. For

ground loop voltages from a low impedance source a resistive

ground wire is totally ineffective, and the difference of

potential between the weapon ground and instrumentation

ground must be measured and subtracted from the measurement.

The purpose of the common lead in the cable is to carry

the weapon ground voltage to the input of the differential

amplifiers, where it is subtracted from the p-c voltages.

The other four wires in the cable carry the p-p and both

p-c voltages to the instrumentation amplifiers.

7
5. CABLE ADAPTER

The signal produced by the diode detector undergoes a

voltage division due to the series resistance of the cable

wire (.4 to 4 megohm) and the input impedance of the

instrumentation amplifier. The equation is the very familiar

V = ^amj^

ampl Z _ , + Z , , detect * ^

' ^ ampl cable

There are two different lengths of cable, and these can

be combined in many different ways. Some have resistances

10 times that of a single cable length. It is important

that Z , , does not have significant effect in equation 1. cajDxe

The only way to do this is to make Z^^^^^ as large as possible

(at least 10 times larger in actual amplifiers) ; then the

ratio of impedances is nearly unity and

^ampl ^detect

This high input impedance of the amplifiers has the adverse

property of allowing the amplifier input voltage to vary

when the driving source impedance is very high. For example,

static charge on persons using the equipment could be

coupled through the small capacitance between hand and wire

and produce a measurable output on the recorder. Also,

nearby power leads could induce 60 Hz signals into the

system.

To reduce these difficulties the cable is terminated

with one megohm resistors at the VIDEED. These resistors

tend to balance out stray signals. Ideally, these resistors

8
should be placed inside the VIDEED itself, but it was not

possible to make stable, high-resistance devices in a small

enough size with the resistor materials presently available.

As an alternative a small [7 mm (0.275") dia. X 22.23 mm (7/8")]

adapter containing the four 1/8 watt, 1 megohm resistors was

constructed and attached to the VIDEED. Figure 1 shows the

p-p wires shunted together by one resistor. Each of the p-c

lines are shunted to the common point or ground. Notice that

pickup on either p-c lead is bypassed to weapon ground through

the 1 megohm resistors. Therefore, pickup on the common lead

is grounded in a similar fashion by inserting the series 1

megohm resistor in that line. Pickup is kept more nearly

equal this way, and the difference voltage applied to the

amplifiers is much smaller. The last bit of pickup ripple

is filtered in the amplifier, but this filtering was kept to

a minimum to allow faster system response.

Besides containing the shunting resistors, the adapter

provides an interface between the five-pin connector

configuration of the VIDEED and the seven-pin connectors on

the cables.

6. INSTRUMENTATION AMPLIFERS

The fundamental purpose of the instrumentation amplifiers

is to present a high impedance to the cable voltages and a low driving impedance to the recorder with a unity gain. It

was later decided that the p-p amplifiers would be more

desirable having a gain of 10.

9
Notice in figure 3 that there are no shunting resistors

on the input to the amplifiers. This allowed the full

4 0 megohms input impedance to appear at the cable. When

the cables were not connected, operating these amplifiers

without an input ground return occasionally damaged them.

Each amplifier was interlocked to the cable so that the

power would be removed from the amplifier as soon as the

cable was disconnected.

The circuitry is standard for instrumentation amplifiers

with two exceptions. The first unusual circuit is the

analog "OR" gate. The two p-c voltages appear at their

respective inputs to the "OR" gate. Whichever voltage is

more positive appears at A and reverse biases the opposite

diode. Beside biasing the diode off, it feeds back a signal

to the op-amp having the lower input signal and effectively

shuts off that amplifier. The end result is a unity gain

circuit for the larger signal and a circuit which approaches

zero gain for the smaller signal. The final amplifier is

simply a driving source for the recorder.

Secondly, a circuit was required to sense when the

amplifiers were being driven into saturation. The saturated

amplifiers produced a net zero output in the differential

amplifiers, giving an indication of no signal present when

in fact there was a very large signal. Saturation of any

amplifier lights an LED on the amplifier front panel as a warning. The circuit is shown in figure 4 and connects to

the amplifier at tie points 1, 2, 3, 4, 5 and 6.

The diode matrix allows the output of each op-amp to

be sensed without causing an interaction between them. The

transistors are emitter followers which light the LEDs

through the appropriate zener diode. The LED is energized

when zener breakdown is exceeded; this occurs when the

amplifier outputs reach 10 volts.

10
For this particular circuit the saturation light will

also glow when the differential signal exceeds three or

four volts. This is not indicative of saturation but does

indicate operation which could damage the SEMs and is a cause to check the measurement setup. Saturation due to

excessively large signals coming through the input cable

has not caused damage to the amplifiers. This is probablydue to the high impedance of the cable, which limits the

input current to a safe value.

The accuracy of the gain (unity for p-c and 10 for p-p)

in the amplifiers is better than can be resolved on the

recorders presently used with the system and is considered

more than adequate for EED measurement requirements.

7 . RECORDERS

Almost any strip chart or x-y recorder can be used to

indicate the output. The one used should have at least

300 ohms input impedance and an appropriate time axis motion.

Coax cables are supplied with the amplifiers to connect

each unit to its designated recorder input.

8. TESTING THE VIDEED SYSTEM

8.1. DC Testing

The VIDEED system was first dc tested. Two test units

were built to evaluate the various parts of the system, and

these are shown in figures 5 and 6.

The test unit in figure 5 generates dc voltages that

represent outputs of the diode detector and tests all components

of the system with the VIDEED removed. Each potentiometer

controls the voltage to the marked pin of the cable or amplifier and should produce the correct response on the recorder.

11
The common-mode control should produce no effect on recorder

until saturation. The unit in figure 6 supplied appropriate

voltages to the diode detector and evaluates the VIDEED itself.

Rl and R2 are used to obtain various combinations of p-p and

p-c voltages as they might appear on the firing circuits.

R3 controls the common mode voltage which appears to the VIDEED

as a p-c voltage without a p-p component. These two units

are convenient for troubleshooting the VIDEED system.

8.2. RF Sensitivity Testing

The final test for the VIDEED is its response to rf

signals. The problem of whether to measure voltage, current

or power was discussed, and power was chosen since it could

be measured more accurately with the instrumentation available.

Power is a proper measurand, since it requires power to produce

explosive ignition either by bridgewire heating or by

sustained arc. Further research into the relative merits of

measuring VIDEED response to rf voltages and/or currents was

considered beyond the scope of this project.

Basically, two measurements had to be made. One

applied power in push-pull to the input leads, which would

apply a difference of potential across the 2-ohm resistor.

The diodes sense this voltage as a pin-to-pin excitation.

However, the pin-to-case circuits will also sense a signal

and produce an output. The other test mode applied power to

the input leads in-phase, so that while there are voltages

between either pin and ground, there should be no difference

of potential across the 2-ohm resistors. If the commonmode rejection were good enough, no output should be produced

by the p-p detector when the VIDEED is excited in this

mode.

12
Figure 7 shows the basic components of the measuring

system. RF power was fed into the VIDEED on two 50-ohm

transmission lines. The input leads themselves form the

center conductors of these lines and so maintain a 50-ohm

match up to the VIDEED header. The two transmission lines

formed in this way were driven from the two outputs of a 180° hybrid junction. These particular types of hybrids

have the property that the outputs will be in phase when

the input is applied to the 0° port, and they will be 180°

out of phase when the input is applied to the 180° port.

In this way both modes could be easily tested simply by

switching the input. The generator and couplers connected

as a ref lectometer are standard. More accurate measurements

can be made if the ref lectometer is tuned, but a simple one

was considered adequate in view of the accuracy requirements

of this project.

The power absorbed by the coupler and VIDEED combined

was measured as the difference between the incident and

reflected powers. Power absorbed by the hybrid is small

and most of the measured net power actually is absorbed by

the VIDEED.

The incident power applied to the hybrid is partly

absorbed by the VIDEED and partly reflected. This reflected

power appears back at the input port and propagates back

toward the generator so that it can be measured as shown

in figure 7. Some power appears at the fourth arm of the

hybrid (normally terminated) , which is the difference between

the two reflections. Since the VIDEED is constructed to be

electrically balanced, the reflections are nearly equal and

the difference very small. Measurements made at 1 GHz

13
indicate that the reflected power due to unbalance is more

than 20 dB below the reflected power actually being measured,

and therefore negligible error is incurred by ignoring it.

Figure 8 shows the results of measurements made by applyi

7 milliwatts of absorbed rf power to the VIDEED at various fre

quencies . The power was applied in the pin-to-case mode or

the 0° input of the hybrid. The pin-to-oin output, which

should be small in this configuration, is indeed small up to

4 GHz and becomes approximately equal to the p-c voltage at

5 GHz. At these frequencies the stray capacitances in the

microcircuit (VIDEED) and the imperfections in the test jig

begin to produce a large effect on the measurement. Figure 9

shows a similar test made by applying 200 milliwatts of

absorbed power to the VIDEED in the pin-to-pin or 180° mode.

In this case the two outputs are expected to be approximately

the same as they are up to 8 GHz.

Figures 10 and 11 show the linearity of the VIDEED

detectors as a function of input power. These data were taken

at 1 GHz and are considered generally true for all frequencies

although a detailed calibration would have to be performed on

each unit to provide any real certainty. The curves are the

average of results taken from several representative VIDEEDs

.

It should be noted that the p-p output when the input is pinto-case is in fact smaller than the p-c output and has its

own scale on the right edge of the graph.

It should be pointed out that until more work is done on

the complete evaluation of the hybrid and test fixture, these

curves should not be construed as "calibration curves" in the

usual sense. Until this evaluation is complete, the VIDEED

is useful as an indicator of relative values of rf power and

should not be used to determine absolute rf power levels.

However, for the purpose of this project, the VIDEED is

capable of fulfilling the requirement for a relative rf power

sensor.

14
8.3. RF Impedance

It is obvious that the impedance of the VIDEED must be

different for the two firing modes and some work was done to

measure these impedances. Attempts to measure the VIDEED

impedance "through" the hybrid coupler produces results that

indicate a need for further research in measuring unbalanced

impedances in the microwave region. However, for this

research, separate funds would be required. Also, further

analysis and measurement on the Automatic Network Analyzer

could resolve some of the difficulties presently experienced

in this type of measurement.

9. CONCLUSION

As of the completion of this report all five recorders,

15 amplifiers (in 3 packages) , 15 cable assemblies and adapters

will have been delivered to the sponsor. Eleven VIDEED units

have already been sent. Because of production difficulties the

remaining units were faulty at construction and have been

disassembled for repair. Of these, 20 units should be ready

for the final shipment. The major fault was due to a flowing

of the conductive epoxy used in the construction. During the

heat curing, the epoxy often migrated into thin spaces with a capillary type of action. The migrated epoxy could then shortcircuit vital components on the circuit board. These units

have been repaired to the extent that time and funding

permitted.

10. ELECTRICAL AND MECHANICAL SPECIFICATION SUMMARY

A. Diode Detector

Mechanical (see figure 12)

Length — 14.99 mm (0.590") (excluding input leads)

Diameter — 7.0 mm (0.276")

15
Lead wires — 48.26-mm (1.90") -long #18 tinned copper

Case — thin-wall brass

Socket and header -- injection molded plastic. Socket

to mate with special 5-pin plug on cable adapter

Electrical

DC resistance

pin to pin 2.0 ohms ± 0.5 ohms

pin to case 2 75 ohms ± 75 ohms

Useful frequency range -- below 1 GHz to 9 GHz. (Lower

frequency limit has not yet been determined.)

RF input -- no greater than 7.0 V RMS for pin to case

voltages, no greater than 500 mW pin to pin power,

for duration not to exceed 1 minute.

Sensitivity (minimum) -- pin to case approximately

5 0 mv dc output for an incident power of 7 mW

supplied from a 50 ^ system. The pin-to-pin

sensitivity is greater than 100 mV for 200 mW

input.

B. Cable Adapter

Mechanical (see figure 2)

Length — 21.97 mm (0.865") . Diameter -- 8.89 mm (0.350")

Connectors -- special 5-pin plug on diode detector end

of adapter. Cable end uses miniature 7-pin connector to mate with cable connector.

C. RF Transparent Cable

Mechanical

Cable length 15 meters (50 feet) or 6 meters (20 feet)

(one complete set includes two 15 -meter lengths and

three 6 -meter lengths) . These can be connected in

series in any combination.

16
Cable diameter -- 3.56 mm (.140") maximum

Connector diameter -- 8.97 mm (0.353")

Length of connector (measured from mating plane of connector to point on cable where it can be bent

safely) — 38 mm (1.5")

Radius of bending — 12.7 mm (0.5")

Cable jacket material teflon

Number of wire -- 6 teflon carbon wires

Resistance — 400 kO. for 6-m (20 foot) length

1.0 m for 15 -m (50 foot) length

D. Cable-Recorder Interface (unit includes 5 amplifiers

with power supply)

Mechanical

Dimensions — width 206.375 mm (8 1/8"), height 158.75 mm

(6 1/4"), depth 323.85 mm (12 3/4"), weight 5.85 kg

(13 lbs.)

Electrical

Power — 120 volts, 60 Hz, 125 mA. Main power controlled

with front panel switch. Each amplifier turned on

when input cable is attached.

Input — each interface amplifier accepts dc inputs from

one diode detector, one pin-to-pin voltage and both

pin-to-case voltages

.

Input amplitude -- ± 10 volts maximum either differential

or common mode

.

Output amplitude -- ± 10 volts maximum

Pin-to-pin output -- 10 times the pin-to-pin input

voltage

.

Pin-to-case output -- the higher of the two pin-to-case

inputs

.

Amplifier saturation -- indicated by LED's on front panel.

Gain — unity to within ± 2% on p-c and 10 ± 2% on p-p.

Common mode rejection -- 70 dB when not in saturation.

17
E. Dual Channel Recorder

(Any recorder having electrical specifications below

can be used.)

Electrical

Power — 120 VAC 60 Hz.

Input -- 100 mV full scale, 2 channel.

Input connector -- general-purpose jack terminal.

Chart speed — minimum speed at least as slow as 1 mm/sec.

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NBS-n4A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PLMM.K A'l lON OR Kl- POR 1 NO. NBSIR 74-3792. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SLiBTlTLK

Completion of the program to evaluate/improve instrumentation

and test methods for electroexplosive device safety

qualification

5. Publication Date

6. Performing Organization Code

272.50

/. rtu 1 nwt\i^.3) iJaui A. Hudson, Dean b. Melquist,

Arthur T? . Dnrirpjkfl anrl Paul F, Wprnpr

8. [-"erforming Organ. Report No.

9. PERFORMING ORG.ANIZXtION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. F33d15- /z-50i3

11. C'ontract /Grant No.

12. Sponsoring Organization Name and f'omplete Address (Street. City, State, ZIP)

Department of the Air Force

Aeronautical Systems Division (AFSC)

Wright-Patterson Air Force Base, Ohio 45433

13. Type of Report & Period Covered

Final Report

14. Sponsoring Agency C ode

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Qualification of weapon and missile systems for electroexplosive device (FED)

safety has been a continuing problem in the military services. Quantitative measurement of stray energy in EED's has been hampered by limitations of existing sensors.

This report describes a new video diode detector instrumented BED (VIDEED) which

responds to both the normal pin-to-pin energy (which would heat an EED bridgewire)

and to the pin-to-case voltage (which might cause EED ignition due to arcing)

.

Also described in this report are the amplifiers, cables, adapters and

recorders which make up the rest of the measuring system. Mention is also

made of the test procedures used in testing the VIDEED system.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key nord unless a proper name; separated by semicolons

)

Electroexplosive device safety; electromagnetic compatibility; electromagnetic

interference; stray energy sensor.

18. AVAILAHILITY _ L'niimitcd 19. Sl-:c:URITY CLASS

( rmS REPORT)

21. NO. OE PAGES

1-or (Jfficial Distribution. Do Not Release to NTIS

UNCT. ASSIEIED

1 Carder I'rom Sup. of Doc, U.S. Government

Washington, D.C. 20 i02. SD Cat. No. C M

-"rinting Office 20. SE( URI TY C LASS

(1 HIS PAGE)

22. Price

Order I'roni National Technical Information

Springfield, Virginia 221'^! Service (NTIS 1 UNC LASSII' lED

IM (IMM KRL USCOMM-DC 29042-P74
i