Bulk Current Injection Probe Test Procedure

A.H. Systems Injection Current Probe SeriesBulk CurrentInjection ProbeTest Procedure A.H. Systems inc. – January 2005REV A1

A.H. Systems Injection Current Probe SeriesTABLE OF CONTENTSINTRODUCTION3GENERAL INFORMATION4TEST ANTY14 A.H. Systems inc. – January 2005REV A2

A.H. Systems Injection Current Probe SeriesINTRODUCTIONCURRENT PROBE uencyRange10 KHz – 100 MHz1 MHz – 400 MHz300 KHz – 1000 MHz A.H. Systems inc. – January 2005REV AInsertionLoss (dB)33 to 1322 to 1.516 to 1Max continuosPower (Watts)100200100Aperture(inches / CM)1.6” / 4.1cm1.6” / 4.1cm1.6” / 4.1cmDiameter(inches / CM)5.0” / 12.7cm5.0” / 12.7cm5.0” / 12.7cmWeight(lb’s / Kg)6.5 / 2.954.0 / 1.815.5 / 2.53

A.H. Systems Injection Current Probe SeriesGENERAL INFORMATIONINTENDED PURPOSESThis equipment is intended for general laboratory use in a wide variety ofindustrial and scientific applications, and designed to be used in theprocess of generating, controlling and measuring high levels ofelectromagnetic Radio Frequency (RF) energy. It is the responsibility ofthe user to assure that the device is operated in a location which willcontrol the radiated energy such that it will not cause injury and will notviolate regulatory levels of electromagnetic interference.GENERAL DESCRIPTIONInjection Current Probes are used to inductively couple large RF currentsinto conductors passing through their aperture.The conductors are signal, control and power circuits of equipment undertest for conducted susceptibility or immunity.Typical specifications requiring the use of injection probes are: DO-160EN-50081-1IEC 801-6TR-EOP-000063The purpose of the test is to determine that RF signals in the range of 10KHz to 400 MHz, when coupled onto conductors and cable bundles willnot cause failure or degradation of their circuit performance.Bundles of wires will be tested with the injection current probes clampedaround all wires. If primary power wires utilize the same connector ascontrol and signal lines, they will be included in the test.Every primary power wire will be tested as a single circuit. If they arecontained within a bundle, they will be separated and tested.Aircraft flight safety critical equipment will have their wires testedindividually for compliance to DO-160. A.H. Systems inc. – January 2005REV A4

A.H. Systems Injection Current Probe SeriesPROBES AND TEST FIXTURESIn order to carry out a Bulk Current Injection Test, the following probesand fixture will be required: Calibration Test FixtureBroadband Current Probes (Monitor Probes)Injection Current ProbesCALIBRATION TEST FIXTURE, MODEL CPF-530The specifications require a calibration fixture for precalibration.The test fixture is composed of an electrically short section of troughtransmission line. The short section permits the measurement of current inthe center conductor of the line, while the current probe is clamped aroundthe center conductor. The fixture's output terminal is terminated in a 50Ωreceiver, spectrum analyzer or RF voltmeter. A measurement of thevoltage developed by this RF voltmeter permits the calculation of currentflowing in the center conductor. The trough is large enough to permit thecurrent probe to be clamped around the center conductor, with the outerconductor of the trough extending around the current probe's outer shield.A mechanical outline of the fixture and a typical injection probe mounted inthe fixture is shown in Figure 1. This fixture is useable over the frequencyrange of 10 kHz to 400 MHz.BROADBAND CURRENT PROBES (MONITOR PROBES)During the equipment test a broadband current probe (monitoring probe) isclamped around the same wire or wire bundle that the injection probe isclamped around. The broadband current probe shall be calibrated for thetest frequencies and cable of operating with 1 ampere of RF current. Thebroadband current probe shall be located approximately 5 cm from theinjection current probe.INJECTION CURRENT PROBESInjection current probes must be capable of injecting the specified currentlevels into the circuit under test. Each probe has its own technicaldescription and model number, and each has its own individual technicalliterature. A.H. Systems inc. – January 2005REV A5

A.H. Systems Injection Current Probe SeriesTEST METHODSTEST METHOD FOR PRECALIBRATIONDue to the occurrence of large variable circuit impedances and resonancesin cables, a calibration fixture is used to establish the forward power into theinjection probe, which develops defined currents in the calibration fixture.The limits of current are established in a "Precalibration Test Set Up". Thistest configuration is shown in Figure 2.PRECALIBRATION TEST PROCEDUREThis test procedure consists of precalibration to establish the levels offorward power necessary to generate the specification limits while clampedonto the calibration fixture.The precalibration is described in the following, and should be carried outfirst.1) The injection probe will be clamped in the calibration fixture as shown inFigure 2.2) The calibration fixture will be terminated in a 50 ohm, 50 watt RF load atone end and a 50 ohm receiver 30 dB attenuator will be required to protectthe receiver or spectrum analyzer. The VSWR of the terminations at bothends of the calibration fixture will be less than 1.2:1 over the frequencyrange of the test.3) The injection probe receives signal levels from the signal generator andpower amplifier. The limits of injected current in the calibrating fixture areprecalibrated for two levels of current magnitude:a)b)An accept/reject level of current which should not cause amalfunction in the equipment under test.A level of current which will cause a malfunction in theequipment under test, without creating permanent damage toit, or the specification level.4) Precalibration Procedure Stepsa)b) A.H. Systems inc. – January 2005REV AIncrease the test signal to the injection probe until theaccept/reject level of current is flowing in the calibrationfixture.Record the forward power and reverse power necessary togenerate the accept/reject level of current.6

A.H. Systems Injection Current Probe Seriesc)d)e)f)g)Increase the test signal until the specification levels of currentare achieved.Record the forward power and reverse power necessary togenerate the specification levels of current.Repeat steps 1-4 over the required frequency range. Thecalibration frequency range can extend from 10 kHz to 400MHz.The forward power in steps 1-4 identifies the total power fromthe amplifier required to achieve the necessary current levels.The reverse power permits the ability to 1) establish theVSWR of injection probe, 2) the power forward - powerreverse establishes the net power delivered to the loadattached to the calibration fixture.The test report shall document steps 1-4 data.INJECTION OF CURRENT INTO EQUIPMENT CABLES PROCEDUREThe equipment test shall be applied to individual wires and entire cables asrequired by the specifications.A test procedure will be prepared that identifies each wire and cable to betested.In all cases of injected current, the test configuration used shall be asshown in Figure 3.The broadband current probe shall be placed at the specified distance fromthe injection probe. This distance is approximately 5 cm for mostspecifications.EQUIPMENT PROCEDURE TEST STEPS1) Carry out the Precalibration Procedure Steps again in this testconfiguration and record the current from the broadband current probe.2) At each test frequency, increase the signal level until a malfunctionoccurs or until the specification current level is measured by the broadbandcurrent probes.Record the following:Current from the Broadband Current ProbeForward power injectedReverse power injected3) Repeat this test for all frequencies necessary. Measure enoughfrequencies to be sure that all susceptibility levels have been determined. A.H. Systems inc. – January 2005REV A7

A.H. Systems Injection Current Probe Series4) At frequencies where the equipment under test shows susceptibility,reduce the signal levels until the susceptibility stops. Record the same dataas in step 2.SAFETYCaution during all of these tests is advised. High RF voltages and currentsare being generated during these tests. Personnel conducting tests shouldnot come in contact with any exposed metallic items of the test setup.Use extreme care when clamping current probes around uninsulatedconductors. It is advised to de-energize the test item during assembly anddisassembly of the test setup. Place all conductors passing through theaperture of probes in the center of the aperture for additional voltagebreakdown protection. Do not permit the uninsulated current probeconnector and cable connectors to come in contact with the ground plane orother adjacent conductors. A.H. Systems inc. – January 2005REV A8

A.H. Systems Injection Current Probe SeriesFigure 1Mechanical Outline A.H. Systems inc. – January 2005REV A9

A.H. Systems Injection Current Probe SeriesFigure 2Precalibration of Injection Current Probe A.H. Systems inc. – January 2005REV A10

A.H. Systems Injection Current Probe SeriesFigure 3Test Configuration for Current Injectoin A.H. Systems inc. – January 2005REV A11

A.H. Systems Injection Current Probe SeriesANTENNA FORMULAS AND CALCULATIONSA specific Transfer Impedance Factor is associated with each frequency. This number isto be subtracted from the receiver reading in order to convert to dBuAdBµA dBµV (from Receiver) - Transfer Impedance (dBΩ) cable Loss (dB)EXAMPLE:Assume that the frequency of interest is 80 KHz and we need to find the current atthis frequency. Connect the probe per figure 1Frequency: 80 KHzTransfer Impedance: -2.76 dB ohmsCable Loss: 0.1dBReceiver Reading: -33.0dBuVdBµA dBµV (from Receiver) - Transfer Impedance (dBΩ) cable Loss (dB)dBµA -33.0 - -2.76 - 0.1dBµA -30.34When injecting current:Injection current (dB) Input current (dB) - Insertion loss (dB) - Cable lossMaximum power rating : 100 Watts for 30 minutesDo not handle injection probe while testing is in progress.Hazardous voltages may be present. A.H. Systems inc. – January 2005REV A12

A.H. Systems Injection Current Probe SeriesMAINTENANCETo ensure reliable and repeatable long-term performance, annualre-calibration of your current probe by A.H. Systems experiencedtechnicians is recommended. Our staff can recalibrate almost anytype or brand of antenna.For more information about our calibration services or to place anorder for antenna calibration visit our website athttp://www.AHSystems.com or call 1(818) 998-0223. A.H. Systems inc. – January 2005REV A13