1、Designation: E2561 07a (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 r
2、evision. 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 f
3、or 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,nu
4、mber 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
5、 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 pr
6、ior 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 un
7、its 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.2.1.2 inductance, nproperty of an electric circuit or oftwo neighboring c
8、ircuits 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-i
9、n 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 sl
10、ot 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
11、 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 u
12、nit; 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 el
13、ectronics 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 th
14、e 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 thecent
15、er 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 previousv
16、ersion 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 States1figure-eight pattern; the quadrupole loop produces four elec-tromagnetic poles instead of the normal two, thus improvingthe s
17、ensitivity 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 to as a slot.2.1.13
18、splashover, nunwanted actuation caused by a ve-hicle in a lane adjacent to the lane in which a sensor is located.2.1.14 traffc monitoring device, nequipment that maycount and classify vehicles and measure vehicle flow charac-teristics such as vehicle speed, lane occupancy, turningmovements, and othe
19、r parameters typically used to portraytraffic movement.2.1.15 wire loop, none or more turns of loop wire woundin a slot sawed in the pavement.3. Summary of Practice3.1 The major steps in installing an inductive loop detectorsystem are:3.1.1 Preparing plans and specifications,3.1.2 Securing the work
20、zone,3.1.3 Installing underground conduit and pull box,3.1.4 Cutting a slot for the loop wire and lead-in wires,3.1.5 Installing the wires,3.1.6 Twisting the lead-in wires,3.1.7 Testing for proper operation of the wire loop andlead-in wires,3.1.8 Sealing the saw cuts,3.1.9 Splicing the lead-in wires
21、 to the lead-in cable in a pullbox,3.1.10 Connecting the lead-in cable to the terminal strip inthe cabinet,3.1.11 Testing for proper operation of the wire loop, lead-inwires, and lead-in cable assembly, and3.1.12 Connecting the terminal strip to the electronics unit.3.2 Procedures needed to ensure w
22、ork zone safety, trafficcontrol, and installation of conduit, pull box, controller cabinet,and any equipment usually placed in the cabinet, such as theelectronics unit, are not covered by this practice.4. Significance and Use4.1 This practice provides a method for the in-road instal-lation of an ind
23、uctive loop detector that consists of wire loops,lead-in wires, and lead-in cable. The practice is intended forinstalling wires in saw cuts made in the roadway surface andnot for installing preformed loops that may be encased in aprotective enclosure such as plastic conduit. Typical compo-nents of a
24、n inductive loop detector system are illustrated in Fig.1. Modern inductive loop detector electronic units are capableof detecting vehicles even if the wire loop is laid on reinforcingsteel before concrete is placed.5. Procedure5.1 Scale drawings of the installation site showing thegeometry of the r
25、oadway and the exact location of thecomponents of the inductive loop detector in relation to thepavement or lane markings are required. The drawings shallindicate the location and specifications for the wire loop(typically centered in the middle of the lane) and lead-in wires,lead-in cable, pull box
26、es, conduit, power sources, pavementmaterials and sealants, cabinets, and electronic units requiredfor the installation. The accuracy of the drawings has a primaryeffect on the quality of the installation as it provides funda-mental guidance for the installation crew and becomes part ofthe procureme
27、nt package used to acquire the needed compo-nents.5.2 The dimensions of the loops and number of turns areselected according to the types of vehicles to be detected,vehicle under-carriage height, lane width, length of lead-incable, and, for some applications, the data desired. Inductiveloops should n
28、ot be wider than 6 ft (183 cm) in a 12 ft (366 cm)lane. Loops should not be less than 5 ft (152 cm) wide becausethe detection distance between the road surface and the vehicleundercarriage becomes limited as the detection distance isapproximately equal to one-half to two-thirds of the loop width(suc
29、h as, the minimum loop dimension). Since the inductance2The boldface numbers in parentheses refer to the list of references at the end ofthis practice.FIG. 1 Inductive Loop Detector System (Notional) (2)E2561 07a (2012)2of the loop must be greater than the inductance of the lead-incable that is, 21
30、H per 100 ft (69 H per 100 m) of #14 AWGlead-in cable for the loop system to have sufficient sensitivity,Klein et al (2) recommend that the inductance of single loopsand series, parallel, or series-parallel combinations of loops begreater than 50 mH to ensure stable operation of the inductiveloop de
31、tector system. Guidance for the number of turns neededto produce the required inductance value is found in Klein et al(2) as follows: “If the loop perimeter is less than 30 ft (9 m),use three turns of wire; if the loop perimeter is greater than 30ft (9 m), use two turns of wire.” Appendix X1 contain
32、s tablesshowing the inductance values for various size loops andshapes (such as, rectangular, quadrupole, and circular).5.3 Manpower and the type and amount of installationmaterial and equipment must be determined before the instal-lation is begun. The required materials should be available insuffic
33、ient quantities to avoid any interruptions in the installa-tion process. Table 1 contains a typical materials list forconstructing an inductive loop detector. Table 2 containstypical equipment needed to install inductive loops. Theequipment required for traffic control and installation ofconduit, pu
34、ll box, controller cabinet, and any equipmentusually placed in the cabinet are not included.5.4 To protect the integrity of the pavement and loopinstallation, cracks and joints in the roadway pavement shouldnot be located closer than 18 in. (45 cm) upstream ordownstream of the inductive loop detecto
35、r being installed.Some agencies relax this constraint to 1 ft (0.3m) (5). Saw cutsfor other wire loops or other in-roadway sensors must not belocated closer than 2 ft (0.6 m) upstream or downstream of theinductive loop detector being installed (6). The distancebetween lead-in saw cuts shall be 6 in.
36、 (15 cm) minimum untilthey are within 1 ft (0.3 m) of the edge of the pavement or curb,at which point they may be placed closer together (7). Lead-insaw cuts shall not be closer than 12 in. (30 cm) from adjacentloop edges (6).5.5 After securing the work zone with appropriatebarricades, cones, and so
37、 forth to divert traffic from the workarea, mark the pavement to show the size and shape of the loopand lead-in wires to be installed and the required saw cuts.Lumber crayon, chalk, or spray paint is typically used for thispurpose. If available, a template of the proper size and shapefor the wire lo
38、op is recommended. However, a straight edge ora tightened string can be used as a marking guide. It is criticalthat the markings reflect the location shown on the constructionplans.5.6 Cut slots into the roadway pavement for the loop wireand lead-in wires using a pavement saw. Do not allow the sawcu
39、t in the pavement to deviate by more than 1 in. (25 mm) fromthe markings for the cut (7). The depth of the saw cut shall besufficient to allow at least a 1-in. (25-mm) cover of sealant tobe placed above the top loop wire or backer rod if such is used(7, 9). Some agencies use 3 and 4 in. (76 and 102
40、mm) slotdepths for multiple wire-turn loops to prevent future grindingand overlay procedures from destroying the loop (9). Saw cutdepth should be verified at several points during the cuttingprocess to ensure a constant value. The width of the saw cutshall be sufficient to allow encapsulation of the
41、 wires by thesealant. Several methods are available to prevent damage to thewire at the corners of a square or rectangular loop by removingthe 90-deg angle. In the first method, diagonal cuts are sawedat the four corners, allowing a minimum margin of 1 ft (30 cm)from the apparent corner as shown on
42、the left of Fig. 2. WhenTABLE 1 Typical Materials List for 6-ft 6-ft (1.8-m 1.8-m)3-Turn Inductive LoopDescription Quantity/LoopLoop and lead-in wires, such as., IMSA513 or 51-5 (3)200 ft (60 m)ALead-in cable, e.g., IMSA 50-2 (3) 200 ft (60 m) or moreATape34 in. (20 mm) rubber splicingB1 roll per 6
43、loopsLoop sealant (per loop) 6 tubes or appropriate number of galloncontainersSealant per 4 ft (1 m) of lead-in cable 1 tubeCaulking gun 1Backer rod As requiredCement, sand, or talc 1 bagDuct seal for conduit 1 blockPull box (sized as required) 1 per splicing locationConcrete As required per pull bo
44、xSplice kits 1 per loopSolder As requiredSurge voltage protector As requiredConduit As requiredAQuantity varies according to site requirement including loop location.BSome states specify a first layer of PVC tape followed by a layer of rubber tapeor heat shrinkage polyolefin tubing as insulation on
45、the lead-in wire-to-lead-incable splice (4).TABLE 2 Typical Installation Equipment List for Inductive LoopDetectorsItem Description and UsePavement saw Creates saw cut for inserting wires. Typicallya self-propelled 18- to 65-hp saw equippedwith14-to38-in. (6- to 10-mm) thick blade(abrasive or diamon
46、d), water valve, depthgauge, and horizontal guideWater supply Cools diamond blade and cleans out sawedslotsJackhammer Bores holes through concrete curbAir compressor Used with jackhammer and to clean and drysawed slotsChisel and hammer Removes sharp edges at corners of sawcutsBlunt tool316-in. to14-
47、in. (5-mm to 6-mm) thick woodpaddle for seating wire in sawed slotWire twisting tool Provides symmetrical twists in the lead-inwiresTemplate/Straight edge Marks outlines of loops on pavementTrenching machine Creates trench for burying cableundergroundVolt-ohm meter andmegohmmeterTests wires for cont
48、inuity and insulationresistanceInductive loop system analyzer Tests continuity and inductance of inductiveloop detector systemSoldering device Enables soldering of wire connections usinga butane torch with a soldering tip or anelectric soldering iron12-ft (4-m) straight edge,chalk line, marking pain
49、t,crayons, or chalkMarks location of all saw cutsWire cutters, linemans pliers Aids in cutting and splicing wiresFish tape Aids wire pullingMeasuring tape or wheel Minimum of 100-ft (30-m) tape to facilitatemeasurements for placement of loop wiresand lead-in wiresPower drill Facilitates sealant mixingE2561 07a (2012)3applying this method, ensure that the bottom of the saw bladecompletely passes through all intersections creating saw cutsthat are clean and well defined. All jagged edges and protru-sions must be removed with a small chisel and h
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