ASTM_E_2561_-_07a_2012.pdf

Designation:E256107a(Reapproved 2012)Standard Practice for theInstallation of Inductive Loop Detectors1This standard is issued under the fixed designation E2561;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice describes the recommended procedure forinstalling inductive loop detectors in sawed slots in roadwaypavement for use as a traffic monitoring device or to actuatetraffic control devices such as a traffic signal.Although thepractice is not intended for installing preformed loops,thepractice does contain information of value for this type of loopsuch as recommendations for the number of turns of loop wire,number and direction of twists in the lead-in wire and cable,splice location(if needed),and grounding options.1.2 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use.2.Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 electronics unit,na card or free-standing modulethat transmits energy into the wire loops typically at frequen-cies between 20 kHz and 100 kHz;special applications such asvehicle classification may use electronics units that transmit atfrequencies above 100 kHz;electronics units allow control ofsensitivity,frequency,pulse or presence operation,and timingfeatures(that is,delay and extension)in some models andindicate system failures.2.1.2inductance,nproperty of an electric circuit or oftwo neighboring circuits that generates an electromotive forcein one circuit when the current changes in that circuit or in theneighboring circuit;expressed in units of Henrys(H).2.1.3 inductive loop detector,nthose parts of an inductiveloop detector system that consist of the wire loops,lead-inwires,and lead-in cable and which responds to the passage orpresence of a vehicle with a decrease in inductance of the wireloop.2.1.4 inductive loop detector system,n a sensor to detectvehicles and their traffic flow properties,whose major compo-nents are:(1)one or more turns of insulated loop wire woundin a slot sawed in the pavement,(2)lead-in wires extendingfrom the loop wire to a curbside or shoulder pull box(3)lead-in cable spliced to the lead-in wires that extends from thepull box to the controller cabinet,and(4)electronics unithoused in the controller cabinet.2.1.5 insulation resistance,nthe resistance measured witha megohmmeter between a conductor and the outer insulatingjacket of a wire or cable.2.1.6 lead-in cable,nshielded wire that is spliced to thelead-in wires in the pull box and which extends from the pullbox to the controller cabinet,where it is connected to theelectronics unit;also known as home-run cable,transmissionline,or feeder cable.2.1.7 lead-in wires,na continuation of the loop wire thatruns from the physical edge of the loop to the pull box;usuallytwisted together to form a wire pair.2.1.8 loop system sensitivity,nsmallest change of induc-tance at the electronics unit terminals that will result in a signalthat indicates the passage or presence of a vehicle.2.1.9 loop wire,none-conductor insulated wire used forboth the wire loop and the lead-in wire;may be jacketed orencased in tube.2.1.10 pull box,na container that encloses the splicesbetween the lead-in wires and the lead-in cable;when installedunderground,the removable cover is aligned flush with theground surface;also known as a handhole,splice box,orjunction box.2.1.11 quadrupole loop,ntypically a rectangular wireloop configuration with a longitudinal slot extending along thecenter of the loop so that the wire can be installed in a1This practice is under the jurisdiction of ASTM Committee E17 on Vehicle-Pavement Systems and is the direct responsibility of Subcommittee E17.52 onTraffic Monitoring.Current edition approved on,July 1,2012.Published July 2012.Last previousversion published 2007 as E256107A.DOI:10.1520/E2561-07AR12.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 figure-eight pattern;the quadrupole loop produces four elec-tromagnetic poles instead of the normal two,thus improvingthe sensitivity to small vehicles and minimizing splashover;quadrupole loops are also used in a diagonal configuration todetect bicycles(1)2.2.1.12 saw cut,nopening made in the roadway pavementusing a pavement saw into which the wire loop or lead-in wiresare inserted;also referred