technology utilization - nasa€¦ · technology utilization office national aeronautics and space...

NASA SP-5951(01)

TECHNOLOGY UTILIZATION

ILECOPY

ELECTRONIC TEST AND CALIBRATION

CIRCUITS

A COMPILATION

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

https://ntrs.nasa.gov/search.jsp?R=19720014589 2020-04-17T03:39:52+00:00Z

ForewordThe National Aeronautics and Space Administration and the Atomic Energy

Commission have established a Technology Utilization Program for the dissemina-tion of information on technological developments which have potential utilityoutside the aerospace and nuclear communities. By encouraging multiple applica-tion of the results of their research and development, NASA and AEC earn forthe public an increased return on the investment in aerospace research and develop-ment programs.

This compilation presents a wide variety of simple test and calibration cir-cuits for use by the engineer and laboratory technician. The majority of thecircuits contained in the four sections of the compilation have general applicationand are relatively inexpensive to assemble.

Additional technical information on individual devices and techniques can berequested by circling the appropriate number on the Reader Service Card includedin this compilation.

Unless otherwise stated, NASA and AEC contemplate no patent action on thetechnology described.

We appreciate comment by readers and welcome hearing about the relevanceand utility of the information in this compilation.

Jeffrey T. Hamilton, DirectorTechnology Utilization OfficeNational Aeronautics and Space Administration

NOTICE • This document was prepared under the sponsorship of the Nat ional Aeronautics and SpaceAdminis t ra t ion . Neither the United States Government nor any person acting on behalf of the UnitedStates Government assumes any l i a b i l i t y resu l t ing from the use of the i n f o r m a t i o n contained in th i sdocument , or warrants t ha t such use w i l l be free from pr ivate ly owned r ights .

For sale by the Nat iona l Technical I n f o r m a t i o n Service. Spr ingf ie ld . V i r g i n i a 22151. $1.00

ContentsSECTION 1. Testing Electronic Devices and Components Page

Tester Checks Operational Performance of CircuitBreakers 1

Latching Overcurrent Circuit Breaker 1Signal Generator for Testing Microcircuits 2Magnetoresistor Monitors Relay Performance 3Semiconductor Devices Can Be Tested Without Removal

from Circuit 4Novel Circuit Extends Usefulness of Clip-On Ammeter 4Chatter Detector with 1 Msec Response Sensitivity 5

SECTION 2. Instrument and System TestFrequency and Voltage Sensor Circuit 6Automated Verifier Unit for Computer Card Punch

Equipment 6PCM Sync-Loss Indicator 7Recording System Measures Power Transients 7Tester Periodically Registers DC Amplifier

Characteristics 8Variable Load Automatically Tests DC Power Supplies 9Electronic Ripple Indicator 9Electronic Test Device Senses Malfunctions in Test

Instrumentation 10

SECTION 3. Calibration and Reference CircuitsPrecision Calibration-and Reference Voltage Source

for Data Acquisition Systems 10Raster Linearity of Video Cameras Calibrated

with Precision Tester 11Low Value Resistors and Shunts Calibrated

with Modified Double Bridge 12Radiometric Temperature Reference 12Potentiometric Source-Resistance Meter 13Precision Bolometer Bridge 13Calibration of High Voltage Divider 14Strain Gage Transducer Bridge Calibrated Remotely 15

SECTION 4. Simple Test ProceduresLocating Sneak Paths in Electrical Circuitry 15Color Identification Testing Device 16Phase Detector Ensures Proper Phasing in Power

Circuits 17Electrical Continuity Scanner Identifies Connector

Wires 17

Safety Circuit Senses Fuel Ignition 18Detector Circuit Measures Relay Chatter Duration 19Helium Background Suppressor Circuit Improves

Sensitivity of Leak Detector 19Electronic Clamp Circuit Improves Performance

of Ultrasonic Transducer '. 20

Section 1. Testing Electronic Devices and Components

TESTER CHECKS OPERATIONAL PERFORMANCE OF CIRCUIT BREAKERS

The tester shown in the schematic measuresthe triptime of circuit breakers in accordancewith the manufacturer's specifications. The testercan also subject the circuit breaker to a specified

wv OTest Load |

from the circuit breaker if it does not trip priorto the maximum allowable test time. In addition,currents, voltages, and operational times can bemonitored for each relay.

Another application of the tester would be itsuse as a current limiter or overload-current warn-ing device. The components of the test circuit

InputPower

To Relays

current and operational lifetime, with the circuit were selected for minimum cost and micro-breaker's lockout device installed.

The circuit breaker tester contains an elaboratecurrent limiter to protect the device in the eventthat a relay with a short circuit is being tested.A time-delay relay, with ranges applicable to thetripping time of the circuit breakers, is provided.The function of the relay is to remove power

miniaturization capability.Source: C. Cole of

General Electric Co.under contract to

NASA Headquarters(HQN-10340)

Circle I on Reader Service Card.

LATCHING OVERCURRENT CIRCUIT BREAKER

Manufacturers of electrical test equipmentand small appliances, and personnel concernedwith repeated nondestructive preflight testing,should be interested in a latching overcurrentcircuit breaker. It consists of a preset current-amplitude sensor, and a lamp-photoresistorcombination in a feedback arrangement whichenergizes a power switching relay. The ac inputpower is removed from the load at predeterminedcurrent amplitudes.

A double pole latching relay (see fig.) interruptsboth sides of the ac line from the control cir-

cuit and the ac load to be controlled. A 3.9 fi re-sistor (Rl), placed in series with one side oC theline, produces a small voltage drop proportionalto the amount of current drawn by the ac load.A dc voltage to the unijunction transistor (Ql)is supplied by a bridge rectifier. The 15 fi resistor(R2) provides current limiting, and the 47 Mf ca-pacitor (Cl) provides filtering. A 390 fi resistor(R3) supplies temperature compensation for theunijunction transistor. The sensor for the circuitis a combination light dependent resistor (LDR)and lamp assembly.

1

ELECTRONIC TEST AND CALIBRATION CIRCUITS

Latching Relay

, Pyrotechnic Subsystem

AC Load

ResetSignal

As the load current increases, the illuminationfrom the lamp increases and lowers the resist-ance of the light dependent resistor. C2 chargesto the peak point voltage of the unijunctiontransistor, causing it to fire. This action energizesthe latching relay, causing the ac power line tobe disconnected from the load and control cir-cuit.

Source: M. L. Moore ofCaltech/JPL

under contract toNASA Pasadena Office

(NPO-11131)

No further documentation is available.

SIGNAL GENERATOR FOR TESTING MICRO CIRCUITS

A comprehensive semiconductor failure analy-sis requires the electrical isolation of the elementsfrom one another. Since the elements are elec-trically interconnected with metallization stripeshaving widths as small as 0.0003 in., mechanicalsevering with a microprobe often leads tounwanted mechanical damage to the surround-ing metallization stripes or to the silicon sub-strate. A high voltage spike generator, with theelectrical schematic shown in the figure, usescapacitive discharges to isolate individual elements(transistors, diodes, resistors) by selectively opencircuiting the metallization stripes on the silicondie. Selected capacitors are charged to a givenvoltage and abruptly discharged to cause anopen circuit in the stripe. Tungsten carbidemicromanipulator probes are used as contacts to

MicromanipulatorProbe Terminal

PowerSupply

Input

CommonNegativeInputTerminal J,

Curve TracerTerminal

Figure 1a. Assembled Generator, One Half Actual Size.

TESTING ELECTRONIC DEVICES AND COMPONENTS

CurveTermir

Power +

Traceral ^

»4 \-4

MicromarProbe Tei

^9

y--HJ

v«

> DPDT °~SnapSwitch

ipulatminal

Vtor

>

CommonNegative

CapacitorsI. 68 uF, 100

180 uFuF

Figure 1b. Circuit Diagram.

the stripes. A snap switch is set to a chargecondition. This allows the capacitors to chargeand permits the probe contacts to be monitored.The values of the capacitors are 68, 100, or180 juF (or any parallel combination of the three).A capacitance value of 168 MF at 8 V is satisfac-tory for open circuiting a 0.0005 in. wide alumi-num stripe.

Source: G. L. Jacobs, D. F. Kizer,and J. T. Szczepkowski of

Sperry Rand Corp.under contract to

*Goddard Space Flight Center(GSC-11107)


MAGNETORESISTOR MONITORS RELAY PERFORMANCE

The waveforms of electrical relays can bemonitored with a test setup that does not alterthe circuit parameters or degrade relay perform-ance. Malfunctions such as lack of armaturemovement, friction, welded contacts, and low

change in the magnetic flux. The waveform isthen displayed on an oscilloscope. Voltage andcurrent conditions, as functions of time, can beinterpreted to determine the characteristic signa-ture of a given relay.

coil voltage can be determined from the transientwaveforms (signatures). The characteristicsignature of the relay is obtained from measure-ments of the magnetic flux produced undertransient operating conditions. A magnetoresis-tor (or Hall-effect) probe, placed in a recessin the contact end of the relay core, senses a

Source: D. Q. Krebs ofThe Boeing Co.

under contract toMarshall Space Flight Center

(MFS-1754)

Circle 2 on Reader Service Card.


SEMICONDUCTOR DEVICES CAN BE TESTED WITHOUT REMOVALFROM CIRCUIT

The test circuit shown in Figure 1A can be usedfor checking semiconductor device propertieswith the device soldered in place. The operating

shown in Figure IB. A nominal degree of famil-iarity with the ideal waveforms is required for theproper interpretation of the waveforms obtained.

PNPTransistor , o_ TUnder _ C

Horizontal

At 45°Beta is 10 if R4 is at 0

Figure 1A. Electrical Schematic of Test Instrument

PNPTransistor

NPNTransistor

NonlinearTransistor

GoodDiode

DiodeReversedIn Tester

OpenCircuit

ShortCircuit

Figure 1B. Typical Waveforms of Devices Undergoing Test

characteristics are obtained by applying ac volt-ages from Tl and 12 and the dc collector biasvoltages from Bl. With the proper adjustmentand calibration of the test circuit parameters, ap-proximate values of current gain and backwardand forward resistances can be obtained. Typicalwaveforms taken from the oscilloscope are

Source: B. C. Allen ofNorth American Rockwell Corp.


(MFS-1163)


NOVEL CIRCUIT EXTENDS USEFULNESS OF CLIP-ON AMMETER

A^multiple range clip-on ammeter with a con-ventional left-hand zero and a 300 mA range hasbeen converted to a zero-center milliammeter witha ±150 mA dc range. The device is bidirectional,without reversing the input connections, and iteliminates the problems of off-scale readings andloss of real-time data.

The measurement circuit contains a separateregulated power supply with a loop of wire fromthe plus to the minus terminal. A clip-on am-meter probe is attached to the loop and the cur-rent flow is' adjusted to provide a center-scale

Clip-On Probe Circuit Under Test


reading. Temporary scale markings of +150, 0,and -150 mA are placed on the meter face. Awire carrying current from the test circuit is alsofed through the clip-on probe. With this setup,current readings from zero to ±150 mA can betaken without reversing the ammeter connections.

Source: T. J. Vaughn ofNorth American Rockwell Corp.

under contract toManned Spacecraft Center

(MSC-15851)


CHATTER DETECTOR WITH 1 /iSEC RESPONSE SENSITIVITY

This circuit can be used to sense chatter or anopen circuit condition of a relay undergoing vibra-tion, shock, or other environmental tests.

+ 28 Vdc

until the reset switch is actuated. Reset is*possible only if continuity is present at the input.

If the discontinuity is not present for the required

With continuity established between the testterminals, transistors Ql, Q3, and Q4 are non-conducting, while Q2 is saturated. When a dis-continuity occurs, timing capacitor Cl beginsto charge through the resistor network. If thediscontinuity exists for a specified time, the tunneldiode switches to the high voltage point, trans-ferring the available drive current to Q3. Latchupoccurs, and the circuit remains in this condition

T Reset

actuation time, the timing capacitor voltage isquickly discharged by Q2, thus preparing thecircuit for the next discontinuity cycle. ^

Source: T. C. Marshall and E. M. Turnbow ofNorth American Rockwell Corp.


(MSC-15503)



Section 2. Instrument and System Test

FREQUENCY AND VOLTAGE SENSOR CIRCUIT

The frequency and voltage amplitude sensingdevice shown in the figure is an integrator whichcan be used in a wide variety of frequency controlproblems. A typical application would be the sens-

state. The sensing circuit provides a false outputwhen both the input voltage amplitude and thefrequency are within the proper limits. A trueoutput condition exists if either the frequency or

ThresholdLevelIntegrator

RectifierSchmittTrigger

Vi

ing of changes in a clock frequency of 120 kHz.Basic components of the sensor include a thresh-old-level integrator, a half-wave integrator anda Schmitt trigger which functions as a dc leveldetector.

A symmetrical square wave, ranging from0 to -6 V, is integrated and averaged, and thedc equivalent level is used to activate a Schmitttrigger circuit. The output of the Schmitt trig-ger is amplified to provide a 15 mA signal in theGO state and about 90 mA in the NO-GO

V0ut

the amplitude has dropped below 120 ±10 kHzor 4.0 ±0.4 Vdc, respectively. By using additionalflip-flops on the input to the sensor, the circuitcould monitor multiples of the 120 kHz range.

Source: O. Ernst ofNorth American Rockwell Corp.


(MFS-12305)


AUTOMATED VERIFIER UNIT FOR COMPUTER CARD PUNCH EQUIPMENT

SummaryPunch

ShoeConnector

CardPunchVerifierUnit

Data SummaryJunction Box

Output,Adapter

SummaryPunch JunctionBox and Digital-To-DigitalAdapter

Digital-to-DigitalSummaryPunchInterface

An automated verifier unit checks for errorspunched in data processing cards. The unit isreadily adaptable to a variety of commerciallyavailable verifiers. For large card processing

runs, it eliminates manual verifications and man-made decisions.

The operational flow diagram is shown in thefigure. When data are missing between the meas-

INSTRUMENT AND SYSTEM TEST

uring and recording devices, the card punch willnot advance until data become available or thecard is manually released. This makes the unitcompatible with external punch programming andmanual operations, with slight modifications.

Source: N. E. Donlin ofThe Boeing Co.


(MFS-13719)


PCM SYNC-LOSS INDICATOR

The PCM sync-loss indicator can be used tomonitor the quality of data received at groundstations.

The sync-loss detector receives the input signal,(-6 V for a sync lock, and O V (or ground) for async loss) from each PCM ground station. Thissignal is used to trigger a latching relay and lampcircuit for each station. The signals are also gatedto an audio oscillator and speaker circuit sothat, if any station drops sync, the O-V signalwill turn on the oscillator to provide an audiblewarning tone. In the circuit illustrated (twoinput sections are shown), a capacitor is dis-charged to turn on the silicon controlled rectifier,which in turn activates the warning light. At thesame time, a transistor switch closes the groundpath of the oscillator which supplies the audioinput to the speaker.

Source: R. D. Patterson ofPhilco-Ford Corp.


(MSC-12342)


R10

UJT1

Vi

RECORDING SYSTEM MEASURES POWER TRANSIENTS

A transient recording system, with a video re-corder as the basic element, detects the presenceof power transients and marks their locationon magnetic tape for data recovery. The systemalso adjusts the amplitude range of the inputsignals to a range within the limits of the inputcircuitry. An audio preamplifier and mixer areincluded to allow oral identification informationto be recorded simultaneously with the tran-sients.

The video recorder (see fig.) has a frequencyresponse from 10 Hz to 3 MHz and is designedto record a 1-V peak-to-peak video signal. Asignal conditioner reduces the input transientsto less than the 1-V peak-to-peak level and trans-forms the 75 Q input impedance of the recorderto approximately 2 Mfl to prevent overloading ofthe test circuit. The transient detector sensesthe presence of any transients exceeding acalibrated threshold and generates a short dura-


"1

TestPoint

Microphone f—t\^

SignalAttenuator

Audio

TransientDetector

i

AudioMixer

Video In

Audio In

VR-1560VideoRecorder

Signal Conditioner

tion audio tone. This audio tone is recordedon the audio track to provide a reference pointfor locating the transient during playback.

The audio preamplifier raises the output ofthe microphone to the proper mixer input level.The mixer then combines the outputs of thetransient detector and the audio preamplifier,

and this signal is recorded on the audio channelof the video recorder.

Source: J. T. Denson ofSperry Rand Corp.


(MFS-21103)


TESTER PERIODICALLY REGISTERS DC AMPLIFIER CHARACTERISTICS

A motor-driven switch and a recorder (see fig.)periodically measure the gain and zero driftcharacteristics of a dc amplifier during environ-mental testing.

O rMotor

i 02 '

f

.~i,

1

k

>4

FT

,

-o^

^-03f

-— j

4

Selecrt

UnderTest

L_

PSOutput

— **w— <

* 1'

>4

J

i ;

.. 20-1

30H

:

c

5V 'Reference

AmplifierOutput

The motor drives the switch at a selectedrate of one rpm. In position 1, the recorder in-put terminals are shorted to verify that therecorder zero has not changed. In position 2,with no input signal, the recorder registers theamplifier zero drift. In position 3, with a 5-Vsignal applied to a voltage divider, the amplifieroutput voltage recorder registers the zero driftand the gain drift. In position 4, the power supplyis connected to the reference, and the testsetup records one-half of the power supplydrift. Several measurements can be time-sharedon a single recorder trace.

Source: G. E. Wenzel and D. CreeManned Spacecraft Center

(MSC-190)


INSTRUMENT AND SYSTEM TEST

VARIABLE LOAD AUTOMATICALLY TESTS DC POWER SUPPLIES

of the variable potentiometers. In this conditionthe upper limit of the load is 1 A and 5 W. Whenthe function switch is open, the transistors arebiased "on" by the potentiometers, and the upperlimit is raised to 10 A and 300 W. The logarith-mic resistance' potentiometers provide a smooth

1 1 5 Vac

V^°

On-Off Switch

115 Vac

ri

i4 RPMSyn.Motor

_|~LHand Crank

Ammeter Switch

[System Being Tested] V X Axis (Volts)

€>\ Short-Circuit

Current Switch

' Y Axis (Volts)

~V Function Switcho

The power characteristics of low voltage, highcurrent, dc power supplies can be measured andplotted with the circuit shown in the figure. Thecircuit uses three, ganged, logarithmic poten-tiometers driven by a self-reversing synchronousmotor. When the function switch is closed, theemitter circuits of the three transistors are shorted,and the load consists of the parallel resistances

transition from an open circuit to a short circuitcondition. The hand crank can be used tovary the potentiometer settings manually when-ever automatic operation is not desirable.

Source: H. C. Burke, Jr., and R. M. SullivanGoddard Space Flight Center

(GSC-291)


ELECTRONIC RIPPLE INDICATOR

An electronic circuit for monitoring excessiveripple voltage on dc power lines can sense varia-tions from a few millivolts to a maximum of 10V(rms). The instrument could be used wherever

DCTestVo ItageInput

Range iSelectorSwitch ^oo^

01 K/ cZR1

10

-vw-^

R2-AXVV—I

R3Negative DCVoltage

R6

10 ELECTRONIC TEST AND CALIBRATION CIRCUITS

power supply fluctuations might endangersystem operations or damage equipment.

The indicator includes a self-contained dcpower supply, input amplifier stage, and a bridge-type balance circuit which responds to variationsin the ripple voltage. A voltmeter connectedacross the bridge circuit measures the magnitudeof the ripple.

Resistor R7 can be adjusted to set the maximumvoltage level, and R6 adjusted to zero the meter.

A known magnitude of ripple voltage is requiredfor calibration and adjustment of the ripplesensing circuit. The entire device is inexpensiveand is easily packaged in a small chassis.

Source: W. H. Houck and J. K. DavidsonKennedy Space Center

(KSC-10162)


ELECTRONIC TEST DEVICE SENSES MALFUNCTIONS IN TEST INSTRUMENTATION

The electronic test device shown in the figureis used in the test and checkout of complexsystems to differentiate between malfunctions inthe system undergoing test and those within the

c, +28V

1 K 1

Line 1

DI < . 02

Line 2

R3

03

^-^-L, 04 — ^

test instrumentation itself. The origin of themalfunction is quickly isolated. Electronic cir-cuits in the monitor use transistors to commutatesilicon controlled rectifiers by removing thedrive voltage; display circuits are then usedto monitor multiple.discrete lines.

All monitored lines are connected to the "OR"

circuit composed of Dl, D2, and Rl. Thiscircuit detects the presence of pulses on thelines. A composite pulse is passed to the differ-entiation elements Cl and R2, which form anarrow positive pulse. This pulse turns off thecommutation transistor Ql that commutates thesilicon controlled rectifiers D3 and D4, causingthem to reset. The leading edge of the incomingpulse is used to reset the rectifiers, and theremaining period of the pulse fires the recti-fiers on those lines carrying pulses. The con-ducting rectifiers enable the appropriate lampto light, indicating the origin of the malfunction.At least twenty lines can be connected to themonitoring circuit, provided that no more thantwenty lamps are lighted at the same time.

Source: W. M. Miller, Jr., ofThe Boeing Co.

under contract toKennedy Space Center

(KSC-10209)


Section 3. Calibration and Reference Circuits

PRECISION CALIBRATION AND REFERENCE VOLTAGE SOURCEFOR DATA ACQUISITION SYSTEMS

A precision calibration and reference voltagesource for digital data systems dissipates lessthan 10 mW of power and operates continuouslyfor extended periods of time. The hybrid in-

tegrated circuit of the source shown in the figurecontains two monolithic operational amplifiers,Al and A2, assembled on an alumina substrate.Positive feedback with a loop gain of less than

CALIBRATION AND REFERENCE CIRCUITS 11

+ 12 Vdc

<<4

TestPoint#1° '

D$

Test P<#3 o

Test P(a/i a —

1ftft

{ J

Dint

jint

r V\

h

<

A*— r<Al

lx< — i

h^A2

t

HWV- 1

\

"LJHWH

,<

itfh

^ 1S

il- /̂wJ

— /VAA^—

i

I

Test Point#2

Gnd

V*

OUT**1o rH

one is incorporated around Al to constant-cur-rent bias the low-current zener diode Dl. Thisfeedback effectively isolates the positive 12 Vdcsupply and prevents input voltage fluctuations

from affecting the current through Dl. AmplifierA2 buffers the output circuit, prevents loadingof the zener, and provides current drive capability.The gain of Al is adjusted to ensure that theamplifier remains in its active region. Also,proper compensation is used to ensure that a6 dB/octave rolloff is maintained through unitygain. Output #1 is the reference voltage for dataacquisition and output #2 provides the calibra-tion signal.

The low-power precision calibration, and ref-erence voltage source operates with an errorof less than 0.1%, and has excellent line regula-tion properties. The output noise is less than1.5 mV rms at 100 kHz. Loading effects arenegligible, as evidenced by the capability ofthe output voltage to drive a 1 kfl load withno nonlinearity errors.

Source: General Instrument Corp.under contract to

Marshall Space Flight Center(MFS-20950)

Circle 10,on Reader Service Card.

RASTER LINEARITY OF VIDEO CAMERAS CALIBRATED WITH PRECISION TESTER

Video InputVariable Delay

HorizontalSync.

Sen mittTrigger

11 ,1 *

1

One- ShotA

A

B

VerticalSync.

A precision test system (see fig.) calibratesthe raster linearity of vidicon television-cameratubes to within 0.5%. The setup can also be usedin conjunction with a camera and oscilloscope

Visual Read Out

to measure gray-scale response, resolution,and shading.

The calibration technique is based upon meas-uring the time between video camera output


transitions as registered at reticle marks on thevidicon faceplate. A flat white field is used asthe input image to the vidicon for horizontallinearity measurements. As the vidicon beampasses the vertical reticle line, a pulse appearsin the video output. When the beam traversesthe second reticle line, a second pulse is gen-erated; the counter measures the interval betweenthese pulses.

For vertical linearity measurement, a muchshorter portion of a number of horizontal rasterlines is selected. Ideally, a black pulse is gen-erated for only those video lines that traversethe horizontal portion of the desired pair of

reticles and only for the sample period. InputA, generated by the one-shot flip-flop A,provides the proper gate pulse time, approxi-mately equal to one fourth of a TV line time.The trigger is derived from delayed horizontalsync. Input B, generated by the one-shot flip-flop B, provides the gate pulse time, equal to onehorizontal line time.

Source: Radio Corp. of Americaunder contract to

Goddard Space Flight Center(GSC-200)


LOW VALUE RESISTORS AND SHUNTS CALIBRATEDWITH MODIFIED DOUBLE BRIDGE

100 nAAA/ fr

1 1 kfl Power Source

H'l' PolarityReversingSwitch

Direct Reading Ratio set

.Four-terminal resistors can be tested andcalibrated with a double bridge, one half ofwhich is a direct reading ratio set (DRRS) andthe second half consists of regular resistancedecad.e boxes of nominal accuracy. After the

bridge is balanced, the ratio between the unknownresistor and the standard is read from the DRRSdials, to the precision of the DRRS.

Through the use of standard resistors, theexact ratio, including the leads to be used withthe double bridge arrangement, is initiallyestablished, then balanced. The ratio of theunknown to the standard equals the ratio settingon the DRRS dials.

The instrument is simple and inexpensive andprovides a straightforward measurement pro-cedure.

Source: C. R. Miller ofThe Boeing Co.


(MFS-14104)

Circle lion Reader Service Card.

RADIOMETRIC TEMPERATURE REFERENCE

A radiometric temperature reference (RTR) usesa thermistor as both the heating and the sensingelement to maintain its resistance at a preselectedlevel.

The operating temperature of the RTR is con-trolled by varying the value of Rl at the input

of constant current amplifier #1. Amplifier #2,operating in a unity gain mode, inverts the signalpolarity for positive feedback through resistorRl. When the circuit is energized, the resistancevalue of Rl is less than the resistance of thethermistor (T), establishing a gain greater than


unity. During this condition, the voltage acrossthe thermistor increases until it approximates

the power supply voltage. This voltage heatsthe thermistor until its resistance is approximatelyequal to Rl and then decreases to a value neces-sary for maintaining resistance equilibrium.

Source: L. G. Monford, Jr.Manned Spacecraft Center

(MSC-13276)

T» Circle 12 on Reader Service Card.

POTENTIOMETRIC SOURCE-RESISTANCE METER

This meter utilizes the simple power-detect-ing characteristic of ganged, unloaded poten-tiometers to determine the source-resistance ofa generator in the dc to UHF frequency range.(With appropriately scaled resistance and powerdissipation capabilities of the potentiometers, the

Generator

seen by the voltmeter-detector is a maximum of1.3 kfi.

The meter is inherently broadband, is simplein design, and is easy to fabricate. It can deter-mine source-resistance over a wide range of inputpower and is extremely simple to operate, re-

1 '1/( I ./ X-sK <— h

R1

150 ft

; R2 IN I f * x

Ir

Voltmeter-Detector

device can determine the internal resistance of quiring only an adjust-to-peak operation, withelectric cells and batteries in order to estimate direct readout of the resistance on a calibratedthe state of discharge and the remaining usefullife.) A typical application of the meter is shownin the figure.

The coax system has a 50 £2 operational re-sistance, and Rl is 150 fi. R2 is 5 kfi, whichyields a 0.5% loading error in the terminatednetwork of Rs and Rl. The source-resistance

dial.Source: E. C. Oakley of

Caltech/JPLunder contract to

NASA Pasadena Office(NPO-10885)


PRECISION BOLOMETER BRIDGE

An inexpensive precision bolometer calibra-tion bridge has several advantages over moreexpensive, commercially available devices. Thebridge can be manually balanced for dc bias

and balance indication, with either dc or acpower input. In each application, an externalgalvanometer is used for null indication. Totaldc current through the bridge is measured with


Bolometer < >

Thermal Lagunamoer

-

Standard ThermistorIt Thermistor Mount

t

DirectionalCoupler

switcn

1

1

1

1

1

t

ThermistorUnder Test

DC Mode

an external milliammeter, or the voltage acrossthe bolometer may be measured when themilliammeter terminals are shorted.

In the ac mode, the bridge is capable ofmeasuring the impedance of thin-film bolometerswith a 10 kHz, 15 V'signal input.

AC Mode

Source: D. R. White ofNorth American Rockwell Corp.


(MSC-11473)


CALIBRATION OF HIGH VOLTAGE DIVIDER

A simple circuit can be used for fast, accuratein-circuit calibration of a high voltage divider,even when the divider is operated under normalcurrent and voltage load conditions.

Resistors Rl, R2, and R3 (see fig.) make upthe voltage divider to be calibrated. The calibra-tion circuit comprises a low precision re-sistor R4, a high precision potentiometer R5,and switches SI and S_2.

To calibrate a high voltage divider, the dividerinput is applied to the input terminals of thecalibration circuit, S2 is moved to the "cali-brate" position, SI is moved to position 1 andpotentiometer R5 is adjusted until a null isobtained on the null detector. The same pro-cedure is followed for positions 2 and 3 of SI.The three resulting potentiometer readings (PI,P2, P3) of R5 at the null points are used tocalculate the resistance of the divider network.

Rl

R2

R3

DividerOutput

PrecisionDivider

DividerInput

S1^JS2

Calibrate

11 Operate

CalibrationDevice

Source:Argonne National


R5

To NullDetector

R. N. LewisLaboratoryCARG-83)


STRAIN GAGE TRANSDUCER BRIDGE CALIBRATED REMOTELY

A special circuit (see fig.) similar to aWheatstone bridge allows remote electricalcalibration of a strain gage transducer using aconstant current supply. Two resistors in the

R2

out

bridge circuit are shunted by a remotely locatedtwo-pole switch. This unbalances the bridge andprovides an output voltage offset which servesas the calibration voltage. During normal opera-tion of the transducer, the bridge is in

balance unless there is a measurable input(force, pressure, etc.). Such an input unbalancesthe bridge, to produce an output voltage pro-portional to the value of the excitation current,I0. During this mode of operation, the circuitfunctions as a conventional constant-current,strain gage bridge; the resistors merely raise thebridge impedance slightly. Typical values of Rs

would be 100 Q, compared to 400 0 for thegage resistance.

The calibration voltage provided by the shuntresistance calibration remains constant eventhough the strain gages change resistance withchanging temperatures. This permits the remotecalibration of force, pressure, and flow transducersover a wide range of temperatures, without theneed for providing special temperature compensa-tion for the resistance calibration circuit.

Source: P. Postma ofNorth American Rockwell Corp.


(MFS-18596)


Section 4. Simple Test Procedures

LOCATING SNEAK PATHS IN ELECTRICAL CIRCUITRY

Example of a Unit

ml

m2

'999J3

A troublesome phenomenon in the operationof electrical circuitry is the existence of "sneakpaths" (defined as unplanned, closed currentpaths) which degrade performance. These pathscontain unwanted electrical currents which arealmost impossible to locate. Sneak paths can becompletely described, within defined limits, bycircuit diagrams.

The task of segregating the paths from thenormal power loops of circuit diagrams can beaccomplished by direct examination with the aidof the scheme shown in the figures. The approachshown uses a matrix system wherein circuit pin-connections are assigned arbitrary designators.

The format of the matrix is a rectangular


Example of a Matrix

J1J2

J3

K1

K2

L1

Ml

M2

N1

N2

N3

J1

1

0

0

0

0

0

0

0

0

0

0

J2

0

1

0

0

0

0

0

p'

1

0

0

J3

0

0

1

0

0

0

0

0

0

0

0

K1

I)

o0

1

0

0

0

0

0

1

0

K2

0

0

0

0

1

1

0

0

0

0

0

L1

0

0

0

0

1

1

0

1

0

0

0

M1

0

0

0

0

0

0

1

0

0

0

0

M2

0

0

0

0

0

1

0

1

0

0

0

N1

n

i

0

0

0

0

0

0

1

0

D

N2

0

0

0

1

0

0

0

0

0

1

0

N3

0

0

0

0

0

0

0

0

0

0

1

Figure 2.

representation of the possible current pathsthrough a unit. For example, to show the elec-trical path from pin N2 to Kl, place the numeral"1" in the Kl column and N2 row. This "1"entry indicates a conducting path from N2 to K1or from Kl to N2, according to the above def-inition of current paths. In noting the directionof current flow, N2K1 represents positive currentflow (opposite electron flow) from N2 to Kl.Various types of impedances can be listedin the matrix by replacing the 1 with the ap-propriate code number or letter.

Source: T. M. Dannback ofThe Boeing Co.


(MFS-15018)


COLOR IDENTIFICATION TESTING DEVICE

StepdownTransformer

115A/.eoHzi

yT Switch

C Fuse

JUUUuJ

Chassis

Indicator Lights

Light Green 1

Brown andWhite

Gray and White 3

Color Coded Wires

A device for testing color blindness aids in"determining the ability of a technician to identifycolor-coded electrical wires. The device can test

the speed of wire selection, as well as the selec-tion accuracy, under conditions similar to thoseencountered on the job. Certain types of partialcolor blindness which are often missed by stand-ard tests and which produce errors in color-codedetermination can also be detected.

Each loop of the low-voltage test circuitcontains two lamps, a color-coded wire attachedto a male connector plug, and a female con-nector jack. The jacks are mounted on a paneland labeled with the name of the correct colorcode. The two lamps for each circuit are paired,either adjacent to the jacks or on a separatepanel which may be placed so that the examineecannot see the results of his selections.

A correct choice will light two adjacent lamps,and an incorrect choice will light bulbs intwo different rows.

Source: R. Martin, E. Brawner, and W. Pate ofThe Bendix Corp.under contract to

Kennedy Space Center(KSC-10278)


SIMPLE TEST PROCEDURES 17

PHASE DETECTOR ENSURES PROPER PHASING IN POWER CIRCUITS

During the initial application of power to anelectrical system, the phasing of the line voltagesmust be tested to eliminate potentially hazardousconditions and avoid possible equipment damage.

output from the phase shifting and summing net-work passes through a transformer and is recti-fied and filtered. The resulting dc voltage operatesa Schmitt trigger which drives the output stage.

+12VDCO

Detector-Phase Rotation Schematic

The phase rotation detector can be used to detectphase rotation in £ny three-phase power cir-cuit. The detector consumes a nominal amountof power and can be fabricated by using highdensity packaging methods. The device producesa 6 Vdc or 0 Vdc output indicating a phaserotation of ACB or ABC, respectively, of thethree-phase lines (see fig.). The 3-phase, 400 Hzinput is phase shifted and summed in the inputcircuitry, producing no output if rotation is ACBand a positive voltage if rotation is ABC. The

The important features of the detector are itssmall size, high input/output isolation (greaterthan 100 MQ), and high input and output im-pedances.

Source: C. J. Rogers and J. R. Lorchik ofNorth American Rockwell Corp.


(MSC-11855)


ELECTRICAL CONTINUITY SCANNER IDENTIFIES CONNECTOR WIRES

The 'electrical continuity scanner shown in theschematic is ideal for the production line testingof prefabricated cables for large complex elec-trical systems. In the test line operation, oneknown point is electrically connected by atemporary jumper wire to the common post ofthe electrical continuity scanner.

Actuation of the switch to the search posi-tion causes the rotary relays to step or searchuntil either a circuit having electrical continuityis reached or the search switch is released. Thisautomatic stepping is accomplished through theuse of contacts provided on the automaticelectric relay (Rl) to make it free running when

desired. After 10 wires have been scanned, asecond automatic electric .relay (R2) is actuatedthrough one position by a latching relay (LI)that transfers the test set to the next 10 circuits.In this manner, 5 decks with 10 positions can beused to scan 50 circuits in a fully automatic orfree running mode.

If a continuity occurs, a relay is energizedto prevent further search, and a lamp is litto indicate the number of the post providing con-tinuity. The search switch is then released, andthe known endpoint and the post number provid-ing continuity are recorded. The jumper wire ismoved to the next known point and the search


Input28Vdc

TerminalStrips

IndicatorLamps1-10. 11-20.21-3031-40.41-50

1 to 10 11 to 20 31 to 40 41 to 50 Indicator Lamps 1 to 10

procedure is repeated until all wires in the bundlehave been correlated with their respective knownends.

Modifications can be made to the basic planto provide circuitry for scanning up to 250 wires.The scanner can also be used to minimize ter-mination errors in the rapid fabrication of multi-wire electrical cables.

Source: R. A. Diclemente and H. C. Boulton ofNorth American Rockwell Corp.


(MSC-90626)


SAFETY CIRCUIT SENSES FUEL IGNITION

A high-response photosensor, integrated intoa solid state switching circuit, provides an out-put signal which confirms whether the combustionof prepellants has occurred in rocket motor tests.This indication eliminates potential hazards dueto the accumulation of unreacted propellentsprior to ignition.

Upon sensing the ignition light, the circuitenergizes a latch relay, allowing the flow of fuelto continue if the ignition is established withina predetermined sampling time. The sensor circuithas application in oil-burning furnaces, boilerpurge systems, power generation stations, andother areas where fuel ignition is an importantoperating parameter.

Source: J. D. Gillett ofNorth American Rockwell Corp.


(MFS-91892)


SIMPLE TEST PROCEDURES 19

DETECTOR CIRCUIT MEASURES RELAY CHATTER DURATION

A highly accurate chatter detector indicatesthe presence and the duration of contact chatter.The detector unit, constructed almost entirelyof integrated circuits, is ideal for miniaturiza-

The oscillator (excluding the crystal), gate,counters, coincidence detector, and lamp driverare integrated circuits requiring only a minimumof discrete components. The range of the detector

10MHzCrystalOscillator

, Gat6 W r •

iiiN.C. Com. N.O.

IR

10

DiAir

LatchingLamp Driver

TR

10

fferentialplifier

\ Reset

1R

' 10ter

IR

10

\7 \7 \7Reset

— -oTo- 1

0.1 -

i i

1.0 —MSec.

10 T

J

100 —

tion. Important operational features includecomplete versatility in range selection, with nosacrifice in accuracy, and virtual elimination ofperiodic recalibration. The chatter detector util-izes the principle of pulse counting to determinethe chatter interval. The pulses are generated bya crystal-controlled oscillator and are countedby a series of decade counters. The inherentstability and accuracy of the crystal oscillatoreliminates the need for periodic calibration andadjustment.

1000 T

can be changed by switching crystals and/orusing decade, octal, or binary counters. Sinceeach counter output has a lamp, the durationof chatter is bracketed between the two highestilluminated lamps.

Source: L. A. Updegraff ofNorth American Rockwell Corp.


(MSC-15799)

No further documentation u available.

HELIUM BACKGROUND SUPPRESSOR CIRCUIT IMPROVES SENSITIVITYOF LEAK DETECTOR

ManualAdjust

Feedback fromAmplifierOutput

IZI9 Vdc

•To> Amplifier• Input

Off°o J-oOn

A feedback circuit packaged in a separateunit permits the manual adjustment of the zeroreference in a mass spectrometer leak detector.This correction eliminates the helium backgroundwhich normally would reduce the sensitivity ofthe instrument. Amplifier linearity and gainfactors are not affected as is the case with con-ventional leak detectors.

The suppressor circuit can be used in leak de-tection applications where high but stable helium


backgrounds may be encountered, such as insmall test cells.

The operation of the suppressor is as follows:If the helium background is high enough towarrant use of the suppressor, the suppressoris turned on. The suppressor control is adjustedto reduce the background level indication until

the system is operating on the range of highestpermissible sensitivity requirements.

Source: J. J. Walls, Jr., and J. F. Ply ofNorth American Rockwell Corp.


(MSC-17210)


ELECTRONIC CLAMP CIRCUIT IMPROVES PERFORMANCE OFULTRASONIC TRANSDUCER

This electronic clamp circuit improves theperformance of ultrasonic inspection equipmentand simplifies the detection of structural flawsor defects which are located in close proximity

sitivity of the crystal to be utilized. The clampingaction stops'the electrical oscillations of the crys-ta1 tuning circuit immediately following theexcitation pulse and permits the receiver to pick

-12V Test Point

Vin

To Amplifier

To Transducer

to the transducer. Conventional ultrasonic testinstruments employing pulse echo techniquesencounter excessive ringing of the crystaltuning circuit due to the excitation pulse,and this ringing obscures the received echo.

The clamp circuit is synchronized with theexcitation pulse to short out the crystal tuningcircuit for a brief period after the excitationpulse. It then unclamps, permitting the full sen-

up the low-level echoes, thereby permittingthe detection of defects very close to the trans-ducer.

Source: D. C. Erdman ofNorth American Rockwell Corp.


(MFS-11217)


NASA-Langley, 1972

NATIONAL AERONAUTICS AND--SPACE ADMINISTRATIONWASHINGTON, D. C. 20546

OFFICIAL BUSINESSPENALTY FOR PRIVATE USE S300

FIRST CLASS MAIL

POSTAGE AND FEES PAIDNATIONAL AERONAUTICS AND

SPACE ADMINISTRATION

lf Undeliverablc ( Section 158posra, Manual) Do Not Return

''The aeronautical and space activities of the United States shall beconducted so as to contribute . . . to the expansion of human knowl-edge of phenomena in the atmosphere and space. The Administrationshall provide for the widest practicable and appropriate disseminationof information concerning its activities and the results thereof"

— NATIONAL AERONAUTICS AND SPACE ACT OF 1958

NASA TECHNOLOGY UTILIZATION PUBLICATIONS

These describe science or technology derived from NASA's activities that may be of particularinterest in commercial and other non-aerospace applications. Publications include:

TECH BRIEFS: Single-page descriptions ofindividual innovations, devices, methods, orconcepts.

TECHNOLOGY SURVEYS: Selected surveys-of NASA contributions to entire areas oftechnology.

OTHER TU PUBLICATIONS: These includehandbooks, reports, conference proceedings,special studies, and selected bibliographies.

Details on the availability of thesepublications may be obtained from:

National Aeronautics and

Space Administration

Code KT

Washington, D.C. 20546

Technology Utilization publications are part

of NASA's formal series of scientific and

technical publications. Others include Tech-

nical Reports, Technical Notes, Technical

Memorandums, Contractor Reports, Technical

Translations, and Special Publications.

Details on their availability may beobtained from:

National Aeronautics and

Space Administration

Code KS

Washington, D.C. 20546

NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONWashington, D.C. 20546

technology utilization - nasa€¦ · technology utilization office national aeronautics and space...

Documents