Manual - ETS
Contents
1. Current probe Measuring instrument Line Impedance Stabilization Network LISN in the EUT power line One or more pieces of input output stimulating and monitoring equipment for exercising the EUT and monitoring performance All instrumentation including the current probe must be outside of the 30 influence of the Model 7605 magnetic field A spacing of one meter should be adequate Testing EUT for susceptibility immunity consists of three processes starting the EUT selecting test frequencies may be done semi automatically and testing the EUT at the selected frequencies done manually START THE EUT Turn on the EUT allow it to stabilize and then verify it is operating properly Make sure the input output stimulation and monitoring equipment is operating satisfactorily SELECT TEST FREQUENCIES Place this end against EUT Model 7605 Testing Showing Application of Model 7605 1 Position the Model 7605 so that the built in spacer is flat against one surface of the EUT This places it parallel to and 5 cm from the EUT 31 2 Drive the Model 7605 with sufficient current to produce a magnetic flux density 10 dB greater than the applicable limit in MIL STD 46ID 9 but do not exceed 15 A for example 183 dB pT The following chart shows the Model 7605 coil current at the RS101 limits 100 00 1 4 H i1 1I LLL AAT 10 00 Current A e2. 0 01 0 00 Frequency kHz 3 Scan the frequency range from 30 Hz to 100 kHz The scan rate may be three times faster than the rates specified in Table III of MIL STD 462D In the 30 Hz to 100 kHz range the specified rates 0 02f per second for analog scans and 0 01 f steps 1 steps for stepped Scans so for these frequency selecting scans the scan rates can be 0 06fo per second for analog scans and 3 steps for stepped scans 32 Stepped scans must dwell at each frequency for one second fois the tuned frequency not the starting frequency Usually for analog scans the frequency range is broken into octave or decade bands and the scan rate is changed at each band The following table shows suggested bands and analog scan rates For stepped scans the frequencies may be computed using equation 9 Frequency Band Analog Scan Rate Total Scan Time 30 Hz 100 Hz 2 Hz s 35s 100 Hz 200 Hz 8 Hz s 12 5s 200 Hz 400 Hz 17 Hz s 11 8s 400 Hz 700 Hz 32 Hz s 9 35 700 Hz 1 5 kHz 61 Hz s 13 1s 1 5 kHz 3 kHz 127 Hz s 11 8s 3 2 6 kHz 250 Hz s 12s 6 kHz 10 kHz 460 Hz s 87s 10 kHz 20 kHz 850 Hz s 11 8s 20 kHz 40 kHz 1 7 kHz s 11 8s 40 kHz 100 kHz 3 8 kHz s 15 9s Suggested Scan Rates for Analog Scanning EQUATION 9 fa A D where f is the tuned frequency at step n and is the starting lowest frequency If susceptibility is noted sele
3. 462D Model 7605 is used separately during susceptibility immunity testing of Equipment Under Test EUT Use the included nylon bolt to connect the Model 7605 Model 7606 together Do not use a metallic bolt or calibration will be inaccurate Model 7605 o Shown unassembled Shown assembled About Model 7605 Model 7605 is a 20 turn coil of AWG 12 enamel insulated copper wire It is wound in a groove on a coil form made of a polytetrafluoroethylene PTFE material The average diameter of the coil is 12 cm 120 mm e The coil form is extended to provide a built in 5 cm spacer to keep the coil at the required distance from the EUT A slot with a threaded screw hole is cut into the end of the spacer to attach the Model 7606 e The coil is used to expose EUT to magnetic fields in the range of 30 Hz to 100 kHz It produces a magnetic field that has a flux density of 9 5x 10 picotesla per ampere pT A of current flowing in it at an axial distance of 5 cm 50 mm from the center In decibels this is 160 dB pT A The coil can carry 15 Arms root mean square of alternating current with only ambient cooling About Model 7606 Model 7606 is a 4 cm 40 mm diameter electrostatically shielded loop antenna with 51 turns of 7 strand AWG 41 litz wire e Model 7606 is used to calibrate the Model 7605 and associated instrumentation It has a phenolic holder which mounts to the Model 7605 to hold
4. Arms but if this level of coil current is sustained for long periods the coil will become warm It has a coil resistance of approximately 40 mQ and an inductance of approximately 71 8 uH EQUATION 1 Equation 1 derived from 7 gives the relationship between coil current and magnetic flux density CRT 3 d r 107 pT A 422 p Where is the permeability of air in H m 4 10 7 H m N is the number of turns on the coil 20 r is the radius of the coil in m r 0 06 m A is the area of the coil in A ar and d is the distance along the coil axis from its center to the measurement point in m d 0 05 m Equation 1 may be simplified for computation as shown in equation 2 EQUATION 2 21 BUT e 107 pT A I 2r F The result of this computation is 7 9 4955107 pT A which is rounded off to 9 5 107 pT A thus the Model 7605 produces a magnetic flux density of 9 5 x 107 pT A or 160 dB pT A on axis at a distance of 5 cm from its center A current of 15 A will produce a flux density of 142 5107 pT or 183 dB pT 18 7606 Model 7606 is used with Model 7605 to calibrate the 7605 and other instrumentation used in tests With 51 turns of wire in a 4 cm diameter loop it has an effective area of 640 cm an effective diameter of 28 6 cm improving the sensitivity of measurements with a given instrument by more than 30 dB over a small single turn loop The response is tabu
5. Information Bulletin 12 2 0 13 Annual Calibration aan 13 Service Procedure Si rrano a aaen a Aa N Eei 13 3 0 Specifications onere derent 15 Electrical Specifications Physical Specifications rene n t Er rd e tp Hoa e a Eua 4 0 Theory of Operation eene 17 Schematic of 7605 7606 in Calibration 17 Model 7605 4 2 tea E tret io y n etn dc a E pets 18 Equation T nne eite Hae ee e ee ERE be e DE eek Equation 2 7606 m care Eqlation 9 2 nene mre ret dei reete een tent RR Po tees 19 Equation 4 soc sette re ba eo nh At n dau 19 Equation s vcs ceed eei a denn dines eda dra at 20 Edqtlationi Oanes inean na aa ERE dene 20 Equation 7 a Led e b Of 20 Conversion Factors for Model 7606 21 Equation 22 5 0 MIL STD 462D Method 5101 23 2 2 decla cea de e d dee 23 Assembly for Calibration 24 Method RS101 Calibration sseseeseeeneenene nne 25 Required 25 About the Signal Source esssssssseseeeee nennen 26 About
6. connecting any components follow the safety information in the ETS Lindgren Product Information Bulletin included with your shipment The normal design application of the Model 7605 Radiating Loop and Model 7606 Radiating Sensor is the MIL STD 462D Method RS101 EMI testing Additional applications are possible but only the application to Method RS101 is discussed here Method RS101 requires two distinct activities test setup calibration and exposure of the Equipment Under Test EUT to specified magnetic flux densities Operational Cautions CAUTION Large magnetic fields are produced during testing particularly at low frequencies They are capable of affecting calculators and watches and at the RS101 worst case limits they exceed the levels which the Swedish government 10 has set for video display terminals Therefore take these precautions e Keep all calculators watches rings and other metallic objects at least one meter from the Model 7605 during testing e Keep your head and torso at least 90 cm from the Model 7605 during testing below 400 Hz The Model 7606 may be damaged by large currents so do not connect it to the signal source and do not leave it in place during testing 23 Assembly for Calibration For test setup calibration Model 7605 and Model 7606 are assembled together When assembled the two loops are parallel to each other and coaxial with their centers precisely 5 cm apart Do
7. not over tighten the nylon bolt Tighten it to only finger tight do not use a wrench Over tightening may cause the bolt to break blocking the bolt hole and making calibration impossible 1 Place the Model 7606 into the slot Place 7606 into slot on 7605 in the body of the Model 7605 with insert and tighten nylon bolt the BNC connector positioned outside Model 7605 and pointing upward 2 Insert the 3 8 16 nylon bolt Tighten to finger tight 24 Method RS101 Calibration Mount the Model 7605 Model 7606 assembly on a non metallic tripod This helps prevent interaction between the assembly and the surroundings and allows the operator to be hands free near the instrumentation I Model 7605 Model 7606 Measuring Instrument B Signal Source 1 I 5 cm Current Probe Measuring Instrument A Block Diagram Calibration Test Setup During calibration keep the assembly several diameters away from metal objects Space the current probe and other instrumentation at least one meter from the assembly to keep it from the influence of the Model 7605 REQUIRED INSTRUMENTATION Model 7605 Model 7606 assembly Signal source see page 26 for more information e Two measuring instruments see page 27 for more information Current probe see page 27 for more information 25 ABOUT THE SIGNAL SOURCE The signal source may be a signal generator followed by a power ampli
8. 6 ABOUT THE MEASURING INSTRUMENTS The measuring instruments can be radio noise or EMI meters calibrated receivers spectrum analyzers or other tunable narrowband voltmeters These instruments must be accurately calibrated with appropriate correction factors available across the frequency range A number of possible instruments are available Some instruments for example certain automatic spectrum analyzers may require no correction factors since they self calibrate and internally generate and apply a correction factor at each frequency A single instrument can be used for both Measuring Instrument A and Measuring Instrument B indicated in the illustration on page 25 If this is done e The Model 7606 should be loaded by a 50 Q dummy load while the output of the current probe is being measured More importantly the output of the current probe must be loaded by a 50 O dummy load when the output of the Model 7606 is being measured gt Failure to load the current probe in 50 while the measuring instrument is not connected to it may result in unpredictable changes in the impedance inserted into the line by the current probe This may then cause an unknown change in the current flowing in the Model 7605 For convenience during the susceptibility testing of the EUT a spectrum analyzer with a tracking generator may be used for measuring instrument A ABOUT THE CURRENT PROBE The current probe may be a low frequency EMI measuri
9. Model 7605 Model 7606 Radiating Loop amp Loop Sensor User Manual For MIL STD 461D Tests In Accordance With Method RS101 of MIL STD 462D NETS LINDGREN An ESCO Technologies Company ETS Lindgren L P reserves the right to make changes to any product described herein in order to improve function design or for any other reason Nothing contained herein shall constitute ETS Lindgren L P assuming any liability whatsoever arising out of the application or use of any product or circuit described herein ETS Lindgren L P does not convey any license under its patent rights or the rights of others Copyright 1999 2010 by ETS Lindgren L P All Rights Reserved No part of this document may be copied by any means without written permission from ETS Lindgren L P Trademarks used in this document The ETS Lindgren logo is a trademark of ETS Lindgren L P Revision Record MANUAL MODEL 7605 7606 MILSTD 461D RS101 Part 399222 Rev B Revision Description Date A Initial Release April 1999 B Rebrand July 2010 Table of Contents Notes Cautions and About This Manual 5 1 n eere terrent vii 1 0 Introduction 3 eren eterni 9 About Model 7605 CR RERO ERE 10 About Model 76006 rct iade a EE ER D Pe ARR 10 References ndn die ee ih hier ier n i i e EO TER E 11 ETS Lindgren Product
10. both measuring instruments Malfunction of either or both measuring instruments Inaccuracy in the current probe Loose clamping or other malfunction of the current probe Damage to the current probe Magnetic field coupling between Model 7605 and the current probe or measuring instruments Loose fit between Model 7605 and Model 7606 or other incorrect assembly Damage to Model 7605 or Model 7606 Metallic objects particularly magnetic materials in close proximity to Model 7605 and Model 7606 If all instrumentation is operating properly and is accurately calibrated readjust the source to produce the correct output from the Model 7606 Use the ratio or difference in dB between the initial setting of the source to the corrected setting of the source as a correction factor in the later EMI susceptibility measurements Disassembly for Method RS101 Testing Before disassembling Model 7605 and Model 7606 verify that the test signal source is turned off or the output is reduced to zero 1 Remove the 7605 7606 assembly from the tripod 2 Unscrew the nylon bolt 3 Remove the Model 7606 from the Model 7605 29 Method RS101 Testing Model 7605 Current Probe Input Output Stimulation amp Monitoring Equipment Measuring Instrument Power Input Block Diagram RS101 Test Setup This diagram shows EUT and these items of instrumentation e Model 7605 e Testsignal source
11. both windings parallel and coaxial to each other with their centers precisely 5 cm apart The holder of the Model 7606 has a 1 4 20 threaded hole to mount to a standard tripod The Model 7606 is terminated BNC connector near the of the holder For test setup calibration the Model 7605 and Model 7606 are fastened together with a 3 8 16 nylon bolt References 1 MIL STD 462D 11 January 1993 Military Standard Measurements of Electromagnetic Interference Characteristics 2 Method RS101 Radiated Susceptibility Magnetic Field 30 Hz to 100 kHz MIL STD 462D 11 January 1993 pp 103 108 3 IEEE Std 268 1992 American National Standard for Metric Practice ANSI 4 IEEE Std 260 1978 Reaffirmed 1985 IEEE Standard Letter Symbols for Units of Measurement ANSI 5 ANSI C63 14 1992 American National Standard Dictionary for Technologies of Electromagnetic Compatibility EMC Electromagnetic Pulse EMP and Electrostatic Discharge ESD 6 IEEE Std 100 1992 Standard Dictionary of Electrical and Electronics Terms ANSI 7 Ramo Simon and John R Whinnery Fields and Waves in Modem Radio Second Edition John Wiley amp Sons Inc NY 1953 OGeneral Electric Company 1944 1953 pp 90 91 9 Jasik Henry Editor Antenna Engineering Handbook McGraw Hill 1961 p 6 2 9 MIL STD 461D 11 January 1993 Military Standard Requirements for the Control of Electromagnetic Interference Emi
12. ct three or more test frequencies per octave at frequencies where susceptibilities are present For example if five frequencies within an octave show susceptible responses select at least three of them for further testing The three selected should be those with the maximum indication of susceptibility 5 Reposition the Model 7605 successively to a location in each 30 cm by 30 cm area on each surface of the EUT and repeat the previous steps 6 From the total set of data where susceptibility was noticed select three frequencies in each octave of the frequency range from 30 Hz to 100 kHz where susceptibility was found TESTING THE EUT At each frequency determined as a result of selecting test frequencies apply the current to the Model 7605 that corresponds to the applicable limit in MIL STD 461D For accuracy in this process calculate the required loop current using equation 10 Move the loop to search for all possible locations of susceptibility including cables connectors cabinet seams vents and so on EQUATION 10 160 1 10 ai where B is the flux density limit from MIL STD 461D dB pT Model 7606 Calibration Calculations The Model 7606 is designed to conform to MIL STD 462D This sensor is electrically very small which permits performance calculation based on geometry In the table on page 21 the performance is shown in the form of a conversion factor which is used to convert the output voltage in dB uV to th
13. culated based on the dimensions of the sensor Thus the traceability of the manufacturing tools to NIST provides traceability of the electrical performance of the sensor to NIST 37 This page intentionally left blank 38 Appendix A Warranty 3 See the Product Information Bulletin included with your shipment for the complete ETS Lindgren warranty for your Model 7605 Radiating Loop and Model 7606 Radiating Sensor DURATION OF WARRANTIES FOR MODEL 7605 MODEL 7606 All product warranties except the warranty of title and all remedies for warranty failures are limited to two years Product Warranted Duration of Warranty Period Model 7605 Radiating Loop 2 Years Model 7606 Radiating Sensor 2 Years 39
14. e magnetic flux density in dB pT of the field in which the coil is immersed The tolerances in manufacturing are a maximum of 0 05 mm 0 002 inches These tolerances in worst case combination cause a maximum error of 0 06 dB The best accuracy with which the conversion factor can be measured is 1 dB and larger errors are probable Therefore the conversion factor is not measured but is instead calculated to provide the best possible accuracy absolute error lt 0 06 dB 34 CALIBRATION BY CALCULATION Following are the equations used in calculation of Model 7606 performance along with a sample calculation The absolute value of the ratio of the magnetic flux density to the voltage across the connected load BV is given by equation 11 EQUATION 11 BY XO RIR 2 R 5l 22fAN 0 pT uV where R is the resistance of the wire in the loop coil is the resistance of the load at the terminals of the loop f isthe frequency of the field being sensed Hz L is inductance of the loop coil A isthe area of the loop coil m N isthe number of turns on the loop coil and The factor 106 converts the units from tesla per volt to picotesla per microvolt The coil resistance Re is found from the length of wire in the coil and the unit resistance of the wire or it can be measured with a low resistance bridge The length of the wire is the product of the average circumference of the winding and the number of
15. fier or current amplifier The signal generator may be a manual signal generator a tracking generator part of a spectrum analyzer or EMI meter or a computer controlled signal generator A 30 W power amplifier with an output impedance of 0 5 will drive the Model 7605 to about 15 A and produce up to 183 dB pT at the end of the built in 5 cm spacer When the amplifier is set to the 30 W output level it produces a current of almost 15 A in the Model 7605 but the actual amplifier power output is only about 9 W the 30 W amplifier is needed to be able to provide enough current from a 0 5 source At the lower end of the frequency range it would be better to use an amplifier with output impedance lower than 0 5 Q For example if the amplifier had a source impedance of only 0 125 Q the power output capability would need to be only 9 5 W However amplifiers and matching transformers to provide an output impedance of 0 125 are not readily available in the EMC test equipment marketplace but those providing 0 5 are they are typically found in an EMC laboratory equipped for MIL STD 462 testing The power amplifier and coupling transformer used for Method CS101 tests may be used for RS101 tests but the amplifier does not need as much power for RS101 tests Higher impedance amplifiers may be practical at the higher frequencies where much less current is needed to produce the flux densities required in the RS101 EMI susceptibility tests 2
16. gulatory and other product marking information This page intentionally left blank vi About This Manual Numbers enclosed square brackets correspond to the references listed in References on page 11 This manual explains the theory of operation of the Model 7605 Radiating Loop and Model 7606 Radiating Sensor and the use of the set for MIL STD 462D 1 electromagnetic interference EMI testing The scope of this manual includes only the theory of operation calibration and use of Model 7605 and Model 7606 for EMI testing in accordance with Method RS101 2 of MIL STD 462D e The use of Model 7605 and Model 7606 for other purposes electromagnetic compatibility EMC testing is limited only by the ingenuity of the user but uses in addition to MIL STD 462 Method RS101 EMI testing are not included e international system of units SI is used throughout this manual Refer to IEEE Std 268 3 for correct abbreviations and their proper use and IEEE Std 260 4 for the proper use of units with the decibel symbol dB In general definitions of EMC terms are contained in ANSI C63 14 5 and other electrical terms in IEEE Std 100 6 vii This page intentionally left blank viii 1 0 Introduction The ETS Lindgren Model 7605 Radiating Loop and Model 7606 Radiating Sensor are provided as a set and are used together for the test equipment calibration described in Method RS101 of MIL STD
17. lated in the Conversion Factors for Model 7606 table on page 21 and is proportional to the frequency shown in Figure RS101 1 in Method RS101 of MIL STD 462D The voltage induced in the loop ej is proportional to the area of the loop the number of turns the frequency and the average flux density within the area of the loop Equation 3 derived from 8 gives this relationship EQUATION 3 e 2nNAfB V where e is the open circuit loop terminal induced voltage in volts is the number of turns on the loop N 51 A is the area of the loop in square metres nr2 0 02 m J is the frequency in hertz and B is the magnetic flux density in tesla For the Model 7606 the open circuit loop terminal induced voltage in microvolts for a magnetic flux density in picotesla is given in equation 4 EQUATION 4 e 0 403 B The general equation for the conversion factor is given by equation 5 and equation 6 and includes the effects of loop impedance and load impedance 19 EQUATION 5 20 Log B V 4 EQUATION 6 2 2 1 R R 1221 B y R Rp 2fL R V 22fAN where Z is the loop inductance in henries L 0 0001745 15 the loop resistance in ohms R 3 921 Q and Ry is the load impedance in ohms For the Model 7606 equation 6 becomes equation 7 EQUATION 7 P 1 3 921 41202 e10 5 R Y B 1 A 1 10 pT uV V 0 403 f The values in the follo
18. nameled Copper Litz Copper Number of Turns 20 51 Maximum Input Current 15 A Continuous NA Connector Banana Jack Pair Type BNC Female Resistance of Winding 40 mQ 3 90 Approximate Inductance 71 8 uH 175 uH Approximate Physical Specifications The windings on both models have square cross sections with dimensions of approximately 12 mm for the Model 7605 Radiating Loop and approximately 3 175 mm for the Model 7606 Radiating Sensor Model 7605 Model 7606 Height 5 89 cm 2 32 in 13 46 cm 5 30 in Base Width NA 5 08 cm 2 00 in Base Depth NA 1 90 cm 0 75 in Mean Loop Diameter 12 0 cm 4 0 cm 15 This page intentionally left blank 16 4 0 Theory of Operation Schematic of 7605 7606 in Calibration Configuration The following illustration shows the Model 7605 Radiating Loop and the Model 7606 Radiating Sensor as loops or coils separated by a calibration distance of 5 cm Model 7605 20T AWG 12 Model 7606 51T litz 7 x AWG 41 I 1 1 5 Coils coaxial and parallel 17 7605 Model 7605 is used alone to produce AC magnetic field to test Equipment Under Test EUT for susceptibility immunity to magnetic fields in the frequency range from 30 Hz to 100 kHz It consists of 20 turns of AWG 12 enamel insulated copper wire close wound with an average diameter of 12 cm It is capable of carrying 15
19. ng clamp on current probe designed to cover the frequency range from 30 Hz to 100 kHz several manufacturers offer this type of probe The accuracy of the individual calibration is important because it is a key element in setting the test current during EMI measurements The transfer admittance or impedance should be individually calibrated over the frequency range Usually the probe calibration by the manufacturer is adequate but do not rely on a probe that has a calibration reported at a single frequency or has a single conversion factor that is to be applied across the entire frequency range 27 CALIBRATION STEPS Set the signal source to a frequency of 1 kHz and adjust the output to provide a magnetic flux density of 110 dB pT as determined by the reading obtained on instrument A and the relationship B 160 dB pT A This requires a current of 50 dB A or 3 16 mA To determine the current algebraically add the current probe correction factor in dB S to the reading in dB mV on instrument A for example laB mA PF aps Rdg A apomv and y 10 20 Measure the voltage output in dB uV from the Model 7606 on instrument B Verify that the output from the Model 7606 is 42 dB uV 3 dB and record this value If the output from Model 7606 is not within 3 dB of 42 dB uV verify the source current is set correctly and then look for other causes Some possible causes are 28 Inaccuracy in either or
20. ssions and Susceptibility pp 40 41 10 MRP P 1990 8 Testing Visual Display Units Draft National Council for Metrology and Testing Sweden 11 ETS Lindgren Product Information Bulletin See the ETS Lindgren Product Information Bulletin included with your shipment for the following e Warranty information Safety regulatory and other product marking information Steps to receive your shipment Steps to return a component for service ETS Lindgren calibration service ETS Lindgren contact information 12 2 0 Before performing any maintenance follow the safety information in the ETS Lindgren Product Information Bulletin included with your shipment Maintenance of the Model 7605 and Model 7606 is limited to external components such as cables or connectors If you have any questions concerning maintenance contact ETS Lindgren Customer Service Annual Calibration See the Product Information Bulletin included with your shipment for information on ETS Lindgren calibration services Service Procedures For the steps to return a system or system component to ETS Lindgren for service see the Product Information Bulletin included with your shipment 13 This page intentionally left blank 14 3 0 Specifications Electrical Specifications Model 7605 Model 7606 Frequency Range 30 Hz 100 kHz 30 Hz 100 kHz Wire AWG 12 7 41 E
21. the Measuring Instruments sessseseeen 27 About the Current Probe eerie teet theta aenean 27 Calibration Steps rete te He rie d oW eat 28 Disassembly for Method RS101 Testing 29 Method RS101 Testing uA Select Test Frequencies sesssssssssssssessseeeeneee ennt 31 Equation Oa sien cst det dad 33 Testing the EUT e ete ecco teuer 34 Equatiori 10 oae REAL DAE Atene 34 Model 7606 Calibration Calculations 34 Calibration by 35 Equation 11 2 cn edt d t nd 35 Equation 12 room tn e ER eee enim nete 35 Equations 2 25 14 a Eae th endi Debe A ELA RU 36 Equation 14 E ENTE Traceability to NIST Appendix A Warranty Notes Cautions and Warnings 3 Note Denotes helpful information intended to provide tips for better use of the product Caution Denotes a hazard Failure to follow instructions could result in minor personal injury and or property damage Included text gives proper procedures Warning Denotes a hazard Failure to follow instructions could result in SEVERE personal injury and or property damage Included text gives proper procedures 3 See the ETS Lindgren Product Information Bulletin for safety re
22. turns This is shown in equation 12 EQUATION 12 R 2mN 0 A where r is the average radius of the loop coil m p is the unit resistance of the wire 34 02 Q CM m for copper and Ay 55 60 for 7 41 Litz The coil inductance L is found from equation 13 35 EQUATION 13 Ls In 8r a 2 H where isthe permeability of air 4710 7 H m and isthe radius of the coil winding m The ratio B V is put in decibels by equation 14 to become the correction factor CF EQUATION 14 20 Jog B V7 dB pT f 30 Hz r 0 02 m N 51 t a 0 0015 m 50 L 4n10 760 020512 7n 8 0 02 0 0015 2 0 00017452 H Re 2 0 02 51 34 02 55 60 3 92139 EU ND 1 3 92139 50 22309 0 00017452 50 _ 392139 0 2780 0 00017452 50 ye 89270916 V 2230 e 20 02 51 CF 20 log 89270 916 99 01 dB The maximum uncertainty because of dimensional tolerances is 0 06 dB therefore this calculated correction factor has a range of 98 95 dB to 99 07 dB For ordinary measurement work such as the measurements for RS101 it is reasonable to round this correction factor to 99 0 dB 36 TRACEABILITY TO NIST The traceability to NIST is through the mechanical measurements and mechanical calibration of the tools used to manufacture the Model 7606 It can be proven mathematically that for such an electrically small sensor the performance can be accurately cal
23. wing table were calculated from equation 5 and equation 7 using a 50 load and a 600 load These values are the same as in Figure RS101 1 in MIL STD 462D 20 CONVERSION FACTORS FOR MODEL 7606 This table shows that below 15 kHz there is less than 1 dB difference between the values of the conversion factors for the loop loaded in 50 and in 600 Q open circuit and over most of the range the difference is less than 0 6 dB To find values of the correction factor between these values use the interpolation in equation 8 Conversion Factor dB pT pV Frequency kHz 500 600 Q 0 03 99 01 98 41 0 1 88 56 87 96 1 68 56 67 96 3 59 03 58 42 7 51 41 51 06 10 48 73 47 96 13 46 57 45 68 15 45 42 44 44 17 44 44 43 35 20 43 20 41 94 23 42 18 40 73 27 41 07 39 34 30 40 39 38 43 35 39 46 37 09 40 38 72 35 94 45 38 13 34 92 50 37 66 34 01 70 36 46 31 13 100 35 66 28 10 21 EQUATION 8 oe f log f 2 Ifd where CF is the desired correction factor at frequency CF is the correction factor at frequency f just below f and is the correction factor at frequency f just above f For example f 0 1 kHz f 1 0 kHz and f 0 4 kHz then for a 50 O load log 0 4 0 1 CF 88 56 68 56 38 56 22 0 4 0 76 52 dB pT uV log 1 0 0 1 22 5 0 MIL STD 462D Method RS101 Testing Before
Download Pdf Manuals
Related Search