ELF / VLF Electric Field Meter - ETS
Contents
1. 29 Radio Frequency Exposure Emission Standards Pertinent to VDT Frequency Range 30 Appendix A Warranty eren 31 Appendix B Operating Protocols 33 Communication Protocol sssssssesesseeeeeeeen nennen 33 Information Transfer Protocol 33 Probe Commands heiter Oe eh ee eire E Ee Du 34 Error 35 Appendix C References 37 Appendix D EC Declaration of Conformity 41 Notes Cautions and Warnings El 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 El See the ETS Lindgren Product Information Bulletin for safety regulatory and other product marking information This page intentionally left blank vi 1 0 Introduction The ETS Lindgren Holaday HI 3638 ELF VLF Electric Field Meter provides full ELF V2. 7 ETS Lindgren Product Information Bulletin 8 2 0 Maintenance 9 Annual Calibration irc Sg e Fondo 9 Maintenance of Fiber Optics nn 10 Replacement and Optional Parts 11 Service Procedures ssssssssssessseeeneeeen eene enne nennen 11 3 0 Specifications 1 eerte enne 13 HI 3638 Typical Frequency Response 15 4 0 HI 3638 Controls and Connectors 17 Ttansmit Rec lve eite tt E tet id o tani 17 EE 18 Charge so HEU HUI EIL IAAP 18 Ground E 18 ME E 18 5 0 Battery Charger eene een 19 Setting the Voltage nennen nennen nnne 19 Charging the Battery 20 Battery Tips aient ceret den eed 21 Operating Temperature ssssssssssssseeeseeeennneneenn nnne 21 PER 21 6 0 Application coner rere renean 23 Duc 23 Sensor Iheolty tyi ade Lg inedit ner ril a Le 23 7 0 Power Frequency Fields eene 25 8 0 Guidelines for
3. 3638 ELF VLF Electric Field Meter User Manual NIS LINDGREN HOLADAY EMF MEASUREMENT ETS Lindgren Inc 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 Inc assuming any liability whatsoever arising out of the application or use of any product or circuit described herein ETS Lindgren Inc does not convey any license under its patent rights or the rights of others Copyright 1994 2013 by ETS Lindgren Inc All Rights Reserved No part of this document may be copied by any means without written permission from ETS Lindgren Inc Trademarks used in this document The ETS Lindgren logo and Probeview Il are trademarks of ETS Lindgren Inc Revision Record MANUAL HI 3638 Part 600062 Rev Revision Description Date Initial Release July 1994 A Added CE October 1997 B Added Error Codes January 1998 C Updated area code February 2000 D Rebrand March 2009 E Updated electric field information February 2011 Replacement and Optional Parts Specifications Operating Protocols F Added Operating Protocols as April 2011 appendix G Updated Replacement and April 2013 Optional Parts Table of Contents Notes Cautions and 1 0 Introduction cnni
4. E1 E2 E3 E4 E5 EG Communication error for example overflow Buffer full error too many characters contained between the start character and carriage return sequence Received command is invalid Received parameter is invalid Hardware error for example EEPROM failure Parity error 35 This page intentionally left blank 36 Appendix C References ACGIH 1987 Threshold limit values for chemical substances in the work environment adopted by ACGIH with intended Changes for 1987 88 American Conference of Governmental Industrial Hygienists Cincinnati ANSI 1982 Safety levels with respect to human exposure to radiofrequency electromagnetic fields 300 kHz to 100 GHz American National Standard C95 1 1982 American National Standards Institute September 1 Australia 1985 Maximum exposure levels radiofrequency radiation 300 kHz to 300 GHz Australian Standard 2772 1985 Standards Association of Australia January 31 Boivin W S 1986 RF electric fields VDT s vs TV receivers Paper presented at the International Scientific Conference Work With Display Units in Stockholm Sweden May Bracken T D W H Bailey and J M Charry 1985 Evaluation of the DC electrical environment in proximity to VDT s Journal of Environmental Science and Engineering 20 7 745 780 Diffrient N A R Tilley and D Harman 1981 Humanscale 7 8 9 Cambridge Massachusetts MIT Press
5. Banana Jack 13 Operating Temperature 10 C to 40 C 50 F to 104 F Humidity 5 to 95 Relative Humidity Non condensing Isotropicity Single Axis Fiber Optic Connectors Standard FSMA Fiber Optic Cable 200 Micron Graded Index Multimode Readout HI 4416 Digital Readout Control Unit Probe Mount e 1 4 20 UNC tapped hole internal thread e Two 90 degrees apart Battery Battery Type 12 Volt DC 1400 mAh Nickel Cadmium NiCd Current Consumption 35 mA Battery Life 40 Hours Nominal Battery Charger 110 240 VAC 16 Hour Battery Charger Jack 2 5 mm 0 1 in Phone Jack Physical Specifications Height 102 mm 4 in Diameter 305 mm 12 in Weight 0 91 kg 2 Ib 14 HI 3638 Typical Frequency Response Measured at 20 V m 100 1000 10000 100000 1000000 10 Frequency Hz 15 This page intentionally left blank 16 4 0 HI 3638 Controls and Connectors Before connecting or operating any components follow the safety information in the ETS Lindgren Product Information Bulletin included with your shipment Following is a description of the controls and connectors for the HI 3638 ELF VLF Electric Field Meter Transmit Receive ELF OFF VLF Attach fiber optic cables to TRANSMIT and RECEIVE conne
6. and other devices Health Physics 45 No 3 September pp 713 722 Telecom 1984 Telecom Australia occupational health policy amp guidelines Screen based equipment Telecom internal guideline 15 1 Melbourne Victoria September Tell R A 1983 Instrumentation for measurement of electromagnetic fields equipment calibration and selected applications In Biological Effects and Dosimetry of Nonionizing Radiation Eds M Grandolgo S Michaelson and A Rindi NATO Advance Study Institute Series Series A Life Sciences Vol 49 Plenum Publishing Company 39 UK 1986 Advice on the protection of workers and members of the public from the possible hazards of electric and magnetic fields with frequencies below 300 GHz a consultative document National Radiological Protection Board Chilton Didcot Oxon United Kingdom May USAF 1987 AFOSH standard 161 9 occupational health exposure to radiofrequency radiation Department of the Air Force October 12 USSR 1976 Occupational safety standards electromagnetic fields of radiofrequency general safety requirements Official publication GOST 12 1 006 76 of the State Committee on Standards of the Council of Ministers of the USSR Moscow January 22 Weiss M M and R C Petersen 1979 Electromagnetic radiation emitted from video computer terminals American Industrial Hygiene Association Journal 40 pp 300 309 April 40 Appendix
7. BED sef hasn bs BY BODY OF To Cy Xx UM PERSON CONDUCTOR CONDUCTOR s CONDUCTOR l TAIN UN BIN IN ON IN I A Nl ELECTRIC FIELDS ARE PERTURBED BY PRESENCE OF INDIVIDUAL UNDER POWER UNE AND ARE ENHANCED AT THE HEAD REGION OF SLIGHTLY REDUCED ELECTRIC FIELD STRENGTH 25 The previous illustration portrays an electric field environment surrounding typical power transmission line It illustrates a single circuit three phase power line consisting of three separate electrical conductors each having an impressed voltage which is 120 degrees out of phase with its neighboring conductors A shield wire may be present above the three phases of the line this grounded wire acts as a preferred point for lightning strikes which could if unprotected strike the current carrying conductors potentially damaging and removing the line from service for repairs A double circuit line would consist of two sets of the three phase conductors Electric and magnetic fields produced by the power line originate because of the voltages impressed on the conductors and the magnitude of current electricity flowing through the conductors The previous illustration depicts the approximate spatial orientation of these fields electric field lines are shown to be directed such that they terminate at perpendicular angles to the surface of the earth and magnetic field lines are shown as lines encircling the conductors A
8. D EC Declaration of Conformity WETS LINDGREN An ESCO Technologies Company Declaration of Conformity We ETS Lindgren L P 1301 Arrow Point Drive Cedar Park 78613 USA declare under sole responsibility that the Model Part Number 3638 Model Part Name ELF VLF Electric Field Meter Date of Declaration 23 July 1996 to which this declaration relates meets the requirements and is in conformity with the relevant EC Directives listed below using the relevant section s of the following EC harmonized standards and other normative documents Applicable Directive s Authorized Signatories fi gt gt ae af 2 J iem i ETSUndgren LP Bryan Sayler General Manager James C Psencik Vice President of Engineering The authorizing signatures on this Declaration of Conformity document authorizes ETS Lindgren L P to affix the CE mark to the indicated product CE marks placed on these products will be distinct and visible Other marks or inscriptions liable to be mistaken with the CE mark v ll not be affixed to these products ETS Lindgren L P has ensured that technical documentation shall remain available on premises for inspection and validation purposes for a period ending at least 10 years after the last product has been manufactured 41
9. FDA 1984 Procedures for laboratory testing of video display terminals and selected television receivers monitors and viewfinders Winchester Engineering and Analytical Center Winchester MA 01890 May Germany 1984 Gefahrdung aurch elektromagnetische felder schutz von personen im frequenzbereich von 10 kHz bis 3000 GHz VDE 0848 Teil 2 Deutsche Elektrotechnische Kommission im DIN und VDE DKE July Grandolfo M 1986 Occupational exposure limits for radiofrequency and microwave radiation Applied Industrial Hygiene 1 2 July Guy A W 1987 Measurement and analysis of electromagnetic field emissions from 24 video display terminals in American Telephone and Telegraph office Washington D C A report prepared for the National Institutes of Occupational Safety and Health Cincinnati March 16 37 Harvey S M 1982 Characteristics of low frequency electrostatic and electromagnetic fields produced by video display terminals Ontario Hydro Research Division report no 82 528 K Toronto Ontario Canada December 16 Harvey S M 1983a Analysis of operator exposure to electric fields from video display units Ontario Hydro Research Division report no 83 503 k Toronto Ontario Canada December 13 Harvey S M 1983b Characterization of low frequency magnetic fields produced by video display units Ontario Hydro Research Division report no 83 504 K Toronto Ontario Canada November 23
10. Harvey S M 1984a VDU shielding Ontario Hydro Research Division report no 84 327 K Toronto Ontario Canada October 31 Harvey S M 1984b Electric field exposure of persons using video display units Bioelectromagnetics 5 pp 1 12 Harvey S M 1985 Risk assessment of VDU electric and magnetic field exposures Ontario Hydro Research Division report no 85 85 K Toronto Ontario Canada March 29 IRPA 1984 Interim guidelines on limits of exposure to radiofrequency electromagnetic fields in the frequency range from 100 kHz to 300 GHz Health Physics 46 4 pp 975 984 April Joyner K H et al 1984 Electromagnetic emissions from video display terminals VDTs Australian Radiation Laboratory report ARL TRO67 December Mantiply E D 1984 An automated TEM cell calibration system Report EPA 520 1 84 024 U S Environmental Protection Agency Las Vegas NV October NTIS order number PB85 134377 Marha K and D Charron 1983 The very low frequency VLF emission testing of CCOHS video display terminals Canadian Centre for Occupational Health and Safety Hamilton Ontario Canada December Mass 1983 Regulations governing fixed facilities which generate electromagnetic fields in the frequency range of 300 kHz to 100 GHz and microwave ovens 105 CMR 122 000 Commonwealth of Massachusetts Massachusetts Register issue no 379 September 38 MPR 1987 Testing Visu
11. LF extremely low frequency very low frequency capability The HI 3638 covers MPR bands and II for Swedish low emission standards plus HI 3638 ELF VLF Electric Field Meter meets test requirements for IEEE 1140 1994 IEEE standard for the measurement of electric fields HI 4416 Digital Readout Control Unit from video display terminals Tripod not included The HI 3638 is useful in low field intensity measurements such as video display terminals VDTs and computer monitors as well as higher field environments such as power transmission lines and industrial locations The HI 4416 Digital Readout Control Unit is included with the HI 3638 and provides an optically isolated full control digital readout for quick and easy measurements in any sensor orientation An optional HI 4413P Fiber Optic Modem allows for a serial interface 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 2 0 Before performing any maintenance follow the safety information in the ETS Lindgren Product Information Bulletin included with your shipment Maintenance of the HI 3638 is li
12. al Display Units test methods MPR P 1987 2 National Council for Metrology and Testing Stockholm Sweden May 15 1987 NATO 1979 Control and recording of personnel exposure to radio frequency radiation Standardization Agreement STANAG No 2345 February 16 Nylen P U Bergqvist R Wibom and B Knave 1984 Indoor air Swedish Council for Building Research 3 pp 163 167 Olsen W C 1981 Electric field enhanced aerosol exposure in visual display environments Prepared for the Norwegian Directorate of Labor Inspection CMI No 803604 1 Paulsson L E et al 1984 Stralning fran dataskarmar Report a 84 08 National Institute for Radiation Protection Stockholm Sweden February 4 Petersen R C M M Weiss and G Minneci 1980 Nonionizing electromagnetic radiation associated with video display terminals Ocular Effects of Non ionizing Radiation Vol 229 SPIE Society of Photo Optical Instrumentation Engineers Box 10 Bellingham Washington 98227 USA pp 179 186 Roy C R et al 1983 Measurement of electromagnetic radiation emitted from visual display terminals VDTs Australian Radiation Laboratory report ARL TRO53 Yallambie Victoria March Slesin L 1985 New Soviet Population Standard 10 uW cm2 at MW frequencies Microwave News V 5 June pp 1 5 Stuchly M A D W Lecuyer and R D Mann 1983 Extremely low frequency electromagnetic emissions from video display terminals
13. ctor on the HI 3638 When the charging plug is connected the LED on the battery charger illuminates It remains illuminated until the charging plug is disconnected 5 A full charge will be completed after approximately 16 hours of charging Disconnect the charging plug after this amount of time Charging the battery longer than 24 hours could damage the battery cells and reduce battery life 20 Battery Tips If the battery exhibits low terminal voltage during charging or if it appears unable to acquire or maintain an appreciable charge individual cells in the battery may be shorted or damaged If your battery needs replacement contact ETS Lindgren Customer Service OPERATING TEMPERATURE Although NiCd batteries are rated for operation in temperatures from 20 C to 65 C 4 F to 140 F operating the HI 3638 in extreme temperatures significantly reduces operating time The optimum operating temperature range is 20 C to 30 C 68 F to 86 CHARGING The HI 3638 battery does not require periodic deep discharges to reverse the capacity depleting memory effect caused by repeated shallow discharges however undercharging can reduce battery capacity Therefore after the charging procedure is complete verify that the battery is fully charged before resuming field operation 21 This page intentionally left blank 22 6 0 Application Meter The HI 3638 ELF VLF Electric Field Meter is a single axi
14. ctors matching white to white and yellow to yellow Plug the fiber optic cable from the HI 4416 Digital Readout Control Unit into the TRANSMIT connector and RECEIVE connector on the HI 3638 matching white to white for transmit and yellow to yellow for receive 17 When the fiber optic cable is not connected cover the cable and connectors with the protective plastic caps supplied This prevents dirt or other contaminants from entering the connector and causing communication problems See Maintenance of Fiber Optics on page 10 for more information ELF OFF VLF This switch activates and deactivates the HI 3638 as well as the selection of ELF or VLF bands LEDs indicate which band is selected In the ELF or VLF position the HI 3638 is powered by the internal 12 VDC nickel cadminum NiCd battery To prolong battery life set the switch to OFF when not in use Charge A 16 hour trickle battery charger is supplied with the HI 3638 The battery charger can charge the HI 3638 or the HI 4416 Slight overcharging up to 24 hours will not harm the battery however charging the battery longer than 24 hours may degrade battery performance Ground Connect GND to earth ground to establish a reference for the HI 3638 Output Connect an oscilloscope to OUTPUT to observe the waveform of the signal driving the true RMS to DC converter circuit 18 5 0 Battery Charger Setting the Voltage Disconnect the batter
15. cts in general most field measurements should be directed toward assessing the unperturbed values For example unperturbed field strengths or free space values are more easily related to internal induced currents in the body Induced currents represent one potential dosimetric measure of electric field exposure The illustration on page 25 also suggests that the electric field lines which terminate on the earth are essentially purely vertically oriented directly beneath the conductors but at extended lateral distances from the line there can be some horizontal component to the field Thus in measurements of electric fields near power lines it may be important to explore different polarization components of the field to assess the resultant electric fields at points above the earth Measurement of electric field strength under a power line or near any other Source of electric fields may be accomplished by supporting the HI 3638 ELF VLF Electric Field Meter on a non conductive tripod Because of the physical asymmetry in the displacement current sensor it is imperative that the front side of the sensor be directed toward the electric field source In this position the electric field lines which are directed downward toward the earth will strike the correct side of the displacement current sensor resulting in an accurate measurement of the field strength In addition the presence of the operator will tend to perturb the electric field that is bein
16. e searched only one reference was found that offered a quantitative emission limit as a guideline specific to VDTs Telecom 1984 This Occupational Health Policy Guideline for screen based equipment was developed by Telecom Australia for internal use until such time as there is a national standard for VDTs in Australia The guide specifies that the levels of radiation emitted from cathode ray VDTs in the frequency range of 50 Hz to 0 3 MHZ shall be as low as possible and should not at any time exceed an electric field strength of 50 V m measured 30 cm from the terminal 30 Appendix A Warranty See the Product Information Bulletin included with your shipment for the complete ETS Lindgren warranty for your HI 3638 DURATION OF WARRANTIES FOR HI 3638 All product warranties except the warranty of title and all remedies for warranty failures are limited to one year Product Warranted Duration of Warranty Period Model HI 3638 ELF VLF 1 Year Electric Field Meter 31 This page intentionally left blank 32 Appendix B Operating Protocols gt The information in this section is subject to change and is included for reference only The following information assumes that the HI 4413P Fiber Optic Modem or HI 4413USB Fiber Optic to USB Converter was purchased and is communicating directly with the probe Communication Protocol Data Type RS 232 Serial Data Mode Asynch
17. ectrodes is different Another way of viewing this phenomenon is to understand that when immersed in an electric field the external field causes a redistribution of electric charge on the two electrodes and this redistribution or charge is just flow of current a displacement current between the two plates 23 The HI 3638 uses this principle to detect electric fields by measuring the displacement current caused by the ambient field between two closely spaced circular disks By placing such a detector in a known electric field the displacement current can be related directly to the magnitude of the field causing it permitting calibration A circular sensing plate surrounded by a guard ring is used in the HI 3638 and the displacement current developed between this 100 mm diameter disk and a closely spaced 300 mm circular disk electrode is sensed and converted to equivalent electric field strength Because the larger electrode is used as a reference in the measurement process for accurate measurements of electric fields the sensor must be oriented perpendicular to the incident field lines for maximum readings 24 7 0 Power Frequency Fields Before connecting or operating any component follow the safety information in the ETS Lindgren Product Information Bulletin included with your shipment Use care when operating this instrument near energized conductors CAUTION M77 MAGNETIC FIELDS N N TX x N ARE NOT PERTUR
18. er Optic Glass Dual H 491106 02 2 Meter HI 3638 Carrying Case H 491100 Tripod H 491009 Fiber Optic Modem 4413 Fiber Option to USB Converter HI 4413USB USB interface Probeview II Software H 491255 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 11 This page intentionally left blank 12 3 0 Specifications Instrument accuracy is derived from a field calibration using a 30 cm TEM cell creating a known electric field A sinusoidal voltage impressed on the TEM cell is directly measured using a true RMS detector and used to calculate the electric field strength in V m Band 1 ELF Band Il VLF Frequency Range 5 Hz 2000 Hz Bandwidth 3dB 2 kHz 400 kHz Bandwidth 3dB Filter Attenuation 80 dB dec e 80 dB dec below 5 Hz below 2 kHz 40 db dec e 40 dB dec above 2 kHz above 400 kHz Bands and Il Measuring Ranges 4 40 0 4 4 40 kV m F S Measuring Limit 1 V m Linearity 0 5 dB 1 of Full Scale Calibration Accuracy 0 5 dB Calibration Points Display Resolution e 3 1 2 Digit LCD e 0 01 V m Waveform Out Output Sensitivity 1 Volt Full Scale Range Output Impedance 10 Waveform Out Jack 3 5 mm 0 14 in Phone Jack Grounding Jack Standard
19. g measured The operator should remain approximately one to two times their height away from the HI 3638 sensor 28 8 0 Guidelines for Exposure To provide a means for judging the significance of measured electromagnetic field emissions found near a VDT the scientific literature can be examined for information on suggested exposure or emission limits The exposure standards used for the content presented in this manual apply to humans for the purpose of establishing safe working or living environments where electromagnetic fields exist The exposure limits in this manual are those found that correspond most closely to the predominant frequency range of VDTs In some cases the standards apply to occupational exposure environments and in other cases to the general living environment often standards for this latter case are referred to as general population or public exposure limits Traditional approaches to radiation protection principally derived from ionizing radiation protection practices usually differentiate between occupational and public exposure Generally occupational exposure limits are higher more permissive than public limits This is because of the greater uncertainties associated with the general public in the work place employees are generally healthier and possible exposure to potentially hazardous physical agents is usually under much better control For example employers can inform workers of situations w
20. hich should be avoided this is not the case for the general population as a whole Regardless of these considerations it is informative to examine some of the recommended exposure guides that apply to different organizations and or countries 29 Radio Frequency Exposure Emission Standards Pertinent to VDT Frequency Range El Many RF exposure standards are under development or revision The following table should be used only as an orientation to existing standards Standard Frequency E V m H gauss Reference kHz RMS RMS 0 0 1 25000 ACGIH 0 1 4 2500 f 0 6 f 4 30 625 IEEE C95 1 1991 3 100 614 2 05 IRPA gen pop 24 hr 50 60 Hz 5000 1 0 Swedish 0 005 2 25 0 0025 0 25uT Guidelines 2 400 2 5 0 00025 0 25nT UK 1986 occ 750 Hz 50 kHz 2000 1 25 UK 1986 public 750 Hz 50 kHz 800 0 05 USSR public RN Slesin 1985 0 03 0 3 25 Frequency in kHz Guidelines based on what was technically possible not biological effects This table summarizes the electromagnetic field exposure standards found in the literature that either directly apply to the frequency range appropriate to VDT emissions or pertain to a frequency range close to that of interest As can be seen the primary difficulty in applying many RF exposure standards to VDT emission levels is that the applicable frequency range of the standards does not extend down low enough From the literatur
21. ing in the line If the line was carrying a current of 1000 A the magnetic fields indicate an expected maximum value of 175 mG equivalent to 14 A m In addition to the normal variation in field strength which is observed along a line transverse to the power line electric fields beneath power lines are perturbed by the local surroundings This illustration shows the phenomenon of electric field concentration which occurs above the head of a person standing under the line Localized enhancement of the electric field will lead to decreased field strength in other nearby areas Because electric field lines have a tendency to terminate on grounded objects and because the human body is conductive and is electrically near ground potential there tends to be a concentration of field lines at the top of the head This same phenomenon occurs with virtually any grounded object immersed in the electric field environment of a power line and can be confirmed through field measurements 27 This inherent shielding effect of the body unless the body is sufficiently distant from the instrument can lead to inaccurate measures of the electric field strength Depending on the proximity and orientation of the body the perturbation effect of the body can lead to either enhanced electric field strength readings or reduced readings when compared to the true unperturbed field strength While in some cases it may be desirable to determine the enhanced fields near obje
22. mited to eran external components such as cables or _ connectors Warranty may be void if the enclosure is opened 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 Maintenance of Fiber Optics Fiber optic connectors and cables can be damaged from airborne particles humidity and moisture oils from the human body and debris from the connectors they plug into Always handle connectors and cables with care using the following guidelines Before performing any maintenance disconnect the fiber optic cables from the unit and turn off power When disconnecting fiber optic cables apply the included dust caps to the ends to maintain their integrity Before connecting fiber optic cables clean the connector tips and in line connectors Before attaching in line connectors clean them with moisture free compressed air Failure to perform these tasks may result in damage to the fiber optic connectors or cables 10 Replacement and Optional Parts Following are the part numbers for ordering replacement or optional parts for the HI 3638 ELF VLF Electric Field Meter Part Description Part Number Battery Pack 12 VDC H 491069 Universal 12 VDC Trickle Charger H 491063 06 110 240 V Cable Fib
23. ronous Word Length 7 bit Parity Odd Stop Bits 1 Data Rate 9600 baud Information Transfer Protocol The probe responds to commands from another device it transmits no data without first receiving instructions to do so Probe Command Structure Probe Response Structure A command to a probe consists of When the probe completes the command it responds with a string consisting of A command letter e Parameters if required e start character e lt gt a carriage return e The command letter e Data if required e CR a carriage return If an error occurs the probe responds with an error code See page 35 for error codes 33 Probe Commands Probe Description Probe Response Command B Read battery voltage IBxx xx lt CR gt e xx xx battery voltage D1 Read probe data Dxx xxuuu CH e 1 enables short form output e xx xx reading the position of the decimal point depends on the range setting of the probe e uuu units for example _V_ V m mW2 mWicm Rx Set range e x 1 2 3 4 N next range Rx lt CR gt e Rx range currently in use Ux Set unit type e x 1 V m e X 2 mW cm Ux lt CR gt e Ut set to V m e U2 set to mW cm 34 Error Codes If an error occurs the probe will respond with one of the following strings These strings begin with a colon and end with a carriage return
24. s meter responsive to one polarization component at a time designed to be responsive to electric fields including non sinusoidal waveforms from 5 Hz to 400 kHz When the HI 3638 is immersed in an electric field the sensor generates a current An input op amp then generates a voltage which correlates to this sensor current This voltage is fed into a filter which isolates the ELF and VLF ranges and discards the out of band signals The output of the selected filter stage ELF or VLF is passed to a software controlled gain stage with selectable gains of x1 x10 x100 x1k x10k The output of the gain stage is converted to its RMS DC equivalent which is then converted to a digital number This digital number is then converted to a displayable value and sent through fiber optic cable to the HI 4416 Digital Readout Control Unit Sensor Theory Electric fields are measured through the employment of a displacement current sensor displacement current sensor operates on the principle that two parallel conductive flat plate electrodes when electrically connected together will exhibit a displacement current which flows between the two plates when immersed in an electric field This can be visualized by remembering that the electric field between two such plates must be zero when they are connected together because they are at the same potential there can be no electric field between them an electric field exists when the potential on the two el
25. t any particular point in space the field can be determined by the superposition of the fields associated with each conductor because the voltage and current of each conductor is out of phase with that in any of the others and the conductors have some finite spacing between them the resulting electric and magnetic fields are calculated on the basis of the vector sum of fields caused by each of the three conductors At some points the fields can constructively add together causing a relatively elevated field strength At other points the fields from the conductors may destructively add leading to minima in the fields Thus power line fields can have rather complex spatial distributions about the line 26 200 Electric field Magnetic field S 5 150 2 x et Oo 2 2 100 o anny so u 0 0 200 100 0 100 200 Distance to Center of ROW ft Spatial distribution of electric and magnetic field strength beneath a 345 kV transmission line This illustration shows the field distribution for a typical double circuit 345 kV transmission line carrying 1000 A The field strengths have been computed for a height of one meter above the ground from one side of the line to the other and indicate that the maximum electric field strength beneath the 345 kV line is expected to be about 3 4 kV m The maximum magnetic field strength will be dependent on the magnitude of current flow
26. y charger from power before changing the voltage setting AC connector Fuse assembly Viewing window Check the viewing window on the power entry module to verify that the battery charger is set to the proper voltage for your AC power source To change the voltage setting 1 Disconnect the battery charger from power 2 Useasmall screwdriver to loosen and remove the fuse assembly from the power entry module 3 Slide the small board located on the back of the fuse assembly from right to left to remove it 19 4 Rotate the board so the desired voltage is facing up and then reinsert it into the fuse assembly The desired voltage should be visible in the viewing window 5 Firmly re seat the fuse assembly back into the power entry module The battery charger is ready to use Charging the Battery The HI 3638 ELF VLF Electric Field Meter contains a rechargeable nickel cadmium NiCd battery A fully charged battery nominal output voltage of 12 VDC provides up to 40 hours of continuous operation Always check the condition of the battery prior to making measurements Never attempt to charge a non rechargeable CAUTION battery 1 Verify that the battery charger is set to the proper voltage for your AC power source See Voltage Setting on page 19 for more information 2 Connect the battery charger to a power source 3 Switch the HI 3638 to OFF 4 Insert the charging plug into the CHARGE conne
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