SPECIAL SPECIFICATION 1257 Digital Card Rack Non-Invasive Micro Loop Detector Assembly (8 Slot Rack)

1993 Specifications CSJ 0924-06-147, etc. SPECIAL SPECIFICATION 1257 Digital Card Rack Non-Invasive Micro Loop Detector Assembly (8 Slot Rack) 1. Description. This Item shall govern for furnishing, and making operational a Digital Card Rack Inductive Non-invasive Micro-Loop Detector Assembly in designated field locations and equipment cabinets as shown on the plans and as detailed in the Special Specifications. 2. Detector Unit/Detector Unit Card Functional Requirements. The non-invasive, magneto-inductive vehicle detector is the sensing component of a vehicle detection system. The vehicle detector collects traffic data and measures traffic flow parameters that can be installed without saw cutting the road surface, this can be serviced without closing traffic lanes. The non-invasive, magneto-inductive vehicle detectors can be inserted easily into 3 in. diameter plastic conduit previously placed 18 to 23 in. below the road surface using trench less directional drilling or open trenching techniques. Magneto-inductive vehicle sensors are transducers that convert changes in the vertical component of the earth s magnetic fields to changes in inductance. Vehicles containing vertical sections of ferromagnetic material focus the earth s field, and thus increase the magnetic field at the sensor when the vehicle moves over the sensor. When connected to an inductive loop detector with compatible operating specifications, vehicle passage is sensed by looking for an increase in the frequency that results from the decrease in the detector inductance. (1) General Requirements. (a) Non-invasive micro-loop units provided under this Item shall meet or exceed the requirements of NEMA TS-1 1989, latest revision, unless otherwise specified in this specification. (b) The non-invasive micro-loop units shall be digital solid state devices designed for 24 +/- 2.5 VDC operation and card mounting. Each detector channel shall not consume more than 50 ma. (c) Each non-invasive micro-loop unit shall sequentially scan 2/4 detector channels. (d) The front panel of the non-invasive micro-loop unit shall be of metal or an impact resistant plastic material designed to permit easy access to the internal components. 1-10 1257

(e) The detector unit shall have a minimum of 8 sensitivity selections for each channel. (f) Each detector unit channel shall be supplied with the delay and extend output features described below: (1) Delay Output - A variable delay circuit shall be furnished to provide a delayed output. This circuit shall be variable from 0 to at least 30 seconds in one-second increments. Detection of a vehicle shall be delayed for the amount of time selected, therefore providing no detector output until a vehicle has been present in the loop for this length of time. This timing shall reset each time the loop is vacated; however, the delay circuit shall be disabled immediately when logic ground is present on pin 1 for channel A or pin 2 for channel B. (2) Extend Output - A variable extend circuit shall be furnished to provide a carryover output. This circuit shall be variable from 0 to at least 15 seconds in 0.25-second increments or smaller. Detector actuation shall be extended after the vehicle leaves the loop. The timing circuit shall reset after the extension has expired; however, the extend circuit shall not be disabled when logic ground is present at pin 1 or pin 2 of the connector described herein. The timing shall be digital and all programming settings shall be accomplished by thumb wheels or dipswitches. The delay and extend features described above shall both be programmable for a detector channel. (g) Each detector unit channel shall function in the following 2 front panel selectable modes: (1) Presence - When a NEMA class 2 vehicle or larger occupies the center of any of the test micro-loops (except for the class 2 vehicle), the detector unit channel shall maintain a detection output for the length of time the vehicle is in the loop and for the time period programmed for the extend output. (2) Pulse - A vehicle passing over a loop shall cause an actuation lasting between 75 milliseconds and 150 milliseconds. If a vehicle stops in the loop area, the detector unit shall, within 3 seconds, detect subsequent vehicles passing over the unoccupied area of the micro loop. (3) The non-invasive sensor shall detect reliably and consistently changes in the ambient magnetic field of 7 millioerstad or greater when the earth s magnetic field is 200 millioersted [H DC =200 moe] and the peak-to-peak amplitude of the applied inductive current is 40 mamp p- p [I AC =40 mamp p-p ]. This requirement defines the sensitivity to be 2 nanohenries/millioerstad at H DC =200 moe and I AC = 40 mamp-p. (4) The inductance change of the non-invasive sensor shall be directly proportional the changes in the earth s magnetic field. 2-10 1257

(5) The probe inductance shall be between 50µH to 80µH. (8) The nominal operating frequency of the non-invasive sensor shall be between 20 khz and 60 khz. (9) The non-invasive sensor shall operate with drive currents of 2.5 mamp p-p to 175 mamp p-p. (h) Maximum presence time shall be switch programmable from 1 to 5 minutes in one minute increments or less. (i) The detector unit channel, after being actuated continuously for any period, shall regain 100% of the selected sensitivity within 0.5 seconds after the loop is cleared of vehicles regardless of the duration of presence. (j) The loop input for each channel shall be isolated from the detector circuitry by means of an isolation transformer. (k) The outputs from each detector unit channel shall be solid state and optically isolated. (l) A switch or switch position shall be provided on the front panel to disable each channel output. (m) If a detector loop circuit becomes open, the detector unit channel shall produce an output that shall remain until the malfunction is corrected. (n) Upon restoration of electrical power after a power failure of any length, the detector unit channel shall automatically return to its normal state of operation within 2 seconds. (o) In addition to the requirements of NEMA TS 1-15.2.21, the detector unit channel shall continue to operate when the resistance between ground and either loop input is varied from 100 megohms to 50 ohms. (p) The connector on the detector card shall be a 2 x 22 pin PCB edge connector with pins on 0.156" centers and gold flashed contacts. The pin assignments shall be as follows: Pin No. A B C D E F H J K L W Function Logic Ground Detector DC Supply External Reset Channel A loop Input Channel A loop Input Channel A output (collector) Channel A output (emitter) Channel B loop Input Channel B loop Input Chassis Ground Channel B output (collector) 3-10 1257

X Channel B output (emitter) 1 Channel A Delay Inhibit 2 Channel B Delay Inhibit 6 Detector Address Bit No. 0 10 Detector Address Bit No. 1 15 Detector Address Bit No. 2 19 Data Transmit 21 Data Receive (q) All circuit traces shall have a conductivity equivalent to at least 2 ounces per square foot of copper. (r) Lightning protection shall be installed within the non-invasive micro-loop unit. The protection shall enable the amplifier to withstand the discharge of a 10 microfarad capacitor charged to ± 1000 volts directly across the detector input pins with no load present. The protection shall enable the non-invasive micro-loop unit to withstand the discharge of a 10 microfarad capacitor charged to ± 2000 volts directly across either the detector inputs or from either side of the detector inputs to earth ground. For this test, the detector chassis shall be grounded and the detector inputs shall have a dummy resistive load attached equal to 5.0 ohms. (2) Functional Requirements. (a) The detector unit channel shall detect all vehicles which traverse public streets and highways and which consist of sufficient conductive material, suitably located to permit recognition by the detector system. For this specification test vehicles shall be as follows: (1) Class 1 - A standard 10 speed, 26 in. bicycle. (2) Class 2-50 CC motorcycle. (3) Class 3 - Automobile ranging from 1700 to 2000 lb. (4) Class 4 - Standard C-50 tractor-trailer combination. (b) The detector unit channel shall detect all of the vehicles described above with all of the configurations specified herein. (c) The detector unit channel shall detect all vehicles described herein on any of the micro-loop configurations described herein traveling in the speed range of ten miles per hour to 80 miles per hour. 3. Detector Card Rack. (1) General Requirements. The card rack shall accommodate up to 8 detector units. (2) The detector card rack frame shall be fabricated from aluminum and shall have slots set in a modular fashion such that the PCB edge connectors shall plug into the rear while sliding between top and bottom card guides for each module. The top front edge of the rack shall be reinforced to ensure structural rigidity (a 90 4-10 1257

degree bend is acceptable). Mounting flanges shall be provided and be turned outward for ease of access. The detector card rack shall be bolted to a cabinet shelf. It shall be possible to unbolt the rack using single tools. (3) Each slot in the card rack shall mate with a 2 x 22 pin card edge connector with 0.156" pin spacings and match the detector card-edge connector. Key slots shall be between pins B & C and between pins M & N. Each card-edge connector shall be secured to the rack by means of threaded hardware to provide mechanical rigidity while still maintaining ease of replacement. (4) All wiring to the rack shall enter and exit in the lower left rear corner when viewed from the front. It shall be labeled and neatly run to other parts of the cabinet and detector termination panel. (5) The slots shall be numbered 1 to 8 left to right when viewed from the front of the rack. (6) Each rack slot shall be wired as follows: Pin No. Function A Logic Ground B Detector DC Supply C External Reset D Channel A Loop Input E Channel A Loop Input F Channel A Output (Collector) H Channel A Output (Emitter) J Channel B loop Input K Channel B loop Input L Chassis Ground W Channel B Output (Collector) X Channel B Output (Emitter) 1 Channel A Delay Inhibit 2 Channel B Delay Inhibit 6 Detector Address Bit No. 0 10 Detector Address Bit No. 1 15 Detector Address Bit No. 2 19 Data Transmit 21 Data Receive All loop inputs shall be wired with shielded twisted pair leads to improve signal isolation. All grounds within the twisted pair leads shall be connected to a chassis ground bus bar on the back of the rack. (7) The external reset inputs (pin C) shall be bussed to a common point and wired to the Detector Panel. (8) The channel loop outputs (-) shall not be bussed together in the rack assembly. (9) The channels shall be wired to the Detector Panel and labeled as follows: 5-10 1257

Slot Channel Detector No Channel Detector No 1 A 1 B 2 2 A 3 B 4 3 A 5 B 6 4 A 7 B 8 5 A 9 B 10 6 A 11 B 12 7 A 13 B 14 8 A 15 B 16 (10) The Detector DC Supply (Pin B) shall be bussed to a common point and wired to the Detector Panel. (11) The Chassis Ground (Pin L) shall be bussed to a common point and wired to the Detector Panel. (12) The Data Transmit (Pin 19) shall be bussed to a common point and wired to the Detector Panel. (13) The Data Receive (Pin 21) shall be bussed to a common point and wired to the Detector Panel. (14) The Logic Ground (Pin A) shall be bussed to a common point and wired to the Detector Panel. (15) The Data Address Bits No. 0, No. 1, and No. 2 shall be connected to the logic ground as follows: Slot Channels Bit No 1 Bit No 2 Bit No 3 1 1-2 Off Off Off 2 3-4 On Off Off 3 5-6 Off On Off 4 7-8 On On Off 5 9-10 Off Off On 6 11-12 On Off On 7 13-14 Off On On 8 15-16 On On On OFF = not connected, ON = connected to Logic Ground 4. Power Supply. (1) General Requirements. (a) The power supply shall be a shelf mounted, enclosed 24 VDC power supply capable of supplying a minimum of 3.6 amperes. The front panel of the power supply shall provide a power on LED, a power on-off switch, an appropriate sized fuse for the 120 VAC input line, and a connector. The connector shall have a metallic shell which is connected to the chassis ground internally and shall mate with an MS-3106A-18-1SW cable connector. Connector pin terminations shall be as follows: 6-10 1257

PIN A B C D E F G H I J FUNCTION AC Neutral Reserved 120 Vac Line Reserved 24 VDC Output Reserved Logic Ground Chassis Ground Reserved Reserved (b) One Power Supply Cable per power supply shall be furnished and installed in each cabinet as shown on the plans. The wires shall be terminated to bus bars or to terminals on the front of the back panel or detector panels as appropriate. The connections shall be with forked spade lugs or otherwise as needed. Each individual wire shall be cut to the length required to reach the point at which it is to be connected. There shall be a minimum of 10 ft. of cable from the mounting point on the panel to the connector. After all wires have been connected, the power supply cable shall be neatly bundled. 5. Functional Tests. Any or all of the test described may be performed at the Department's Austin facilities. (1) In the presence mode, a class 1, 2, 3 and 4 vehicle stopped over a micro loop with 100 ft. lead-in shall be detected. Class 3 and 4 vehicles shall be continuously detected for a minimum of the time programmed for maximum presence or for at least one half hour. (2) All classes of vehicles moving over a micro loop with 100 ft. lead-in shall generate a single pulse output from the non-invasive micro-loop unit channel in the pulse mode. (3) There shall be no cross talk between adjacent loops connected to separate channels or non-invasive micro-loop units with or without a vehicle on one of the loops after the non-invasive micro-loop unit channels are adjusted. (4) A micro loop connected to a detector unit channel in the presence mode shall detect a class 3 vehicle for not less than 15 minutes and shall, upon departure of this vehicle from the zone of detection recover and, after one second, detect a class 2 vehicle. (5) The micro loop connected to a detector unit channel with 100 ft. of lead-in shall detect class 2, 3 and 4 vehicles. The vehicles shall enter the zone of detection at ten miles per hour and stop. The class 2 vehicle shall be detected for a minimum of three minutes. Class 3 and 4 vehicles shall be detected for the time programmed for maximum presence. 7-10 1257

(6) The micro loop adjusted (sensitivity) for any one class of vehicles shall not detect a numerically equal class vehicle passing 36 in. outside the micro loop's magnetic field sensing perimeter. (7) A class 1 vehicle traveling at ten miles per hour over either a micro loop with 100-ft. lead-in shall be detected. (8) A micro-loop unit channel connected to a non-invasive micro loop shall detect Class 2, 3, and 4 vehicles traveling from 10 miles per hour to 80 miles per hour. (9) All of the above tests shall also be performed with 1000-ft. lead-in. (10) Other NEMA environmental tests may be performed. (11) The Engineer may require that 2 sample detector units, card rack, and power supply be forwarded to the department test facility in Austin for testing. 6. Documentation Requirements. Two complete sets of documentation described below shall be provided for every Digital Card Rack Micro-Loop Assembly for the project. (1) Complete and accurate schematic diagrams. (2) Complete installation procedures. (3) Complete performance specifications (both electrical and mechanical) on the unit. (4) Complete parts list including names of vendors for parts not identified by universal part numbers such as JEDEC, RETMA, or EIA. (5) Pictorial of components layout on circuit board. (6) Complete maintenance and troubleshooting procedures. (7) Complete stage-by-stage explanation of circuit theory and operation. 7. Installation. (1) Physical Requirements. The non-invasive sensor shall have an outer diameter of 0.8125 in. and a height of 2.25 in. The non-invasive sensor shall snap into a carrier. The carrier shall hold and maintain the sensor position to ±2 of vertical. The non-invasive sensor shall be suitably sealed for use in 100% humidity environments in the conduit. (2) Conduit Installation Requirements. The conduit shall be a three in. conduit consisting of Schedule 80 PVC or seamless polyethylene with an inner diameter of 2.9 in. and outer diameter of 3.5 in. The conduit shall be installed at a nominal centerline depth of 21 in. from the road surface following crown line. The depth of the centerline from the road surface shall be maintained between 18 and 24 in. over its entire length. The centerline of the conduit shall not deviate horizontally more than required by then application. Any deviation in 8-10 1257

conduit alignment shall be less than 0.25 in. per ft. At least one end of the conduit shall terminate at a standard size ground box as required by the plans with a nominal 24 in. ground box and extend 3 in. into the ground box. The end of the conduit at the hand hole shall have gravel to permit drainage. (3) Carrier Physical and Installation Requirements. (a) The carrier mechanism for holding and inserting the non- invasive sensor (carrier) shall allow for placement of either single, double, triple or quadruple non-invasive, magneto-inductive vehicle sensors in the 3 in. diameter conduit meeting the installation requirements. (b) The carrier shall allow probes to be placed at 6 in. spacing increments. (c) The carrier shall allow for horizontal placement of the non invasive sensors to be within 3 in. with respect to the specified location referenced at the road surface. (d) The carrier and the non-invasive sensor components shall be readily assembled on-site without special tools. (e) The carrier shall hold up to 12 lead-in cable including the pull rope. (f) The carrier and inter linking mechanism shall have sufficient strength to allow insertion of up to 12 probe sets into a 100 ft. long conduit meeting the installation requirements. (g) The carrier system shall have a locking mechanism to maintain the orientation of all non-invasive sensors within ±2 of vertical. (h) The first carrier (end cap carrier) shall have a rope attached of sufficient strength to assist in the removal of the carriers from the conduit. (4) Installation Verification. (a) The conduit installer shall provide a log of the boring depth measured every 2 ft. in boring distance shall be provided. (b) The installer of the non-invasive sensor, home-run cable and detector shall verify that the installation meets requirements by measuring the inductance of the non-invasive sensor assembly with a properly designed, matched vehicle detector. (c) The inductance shall be the sum of probe inductance, inductance of lead-in cable (16.5 µh per 100 ft.) and home-run cable (23 µh per 100 ft. ) and shall be within ± 20% of the calculated inductance. (d) The installer of the non-invasive sensor, home-run cable and detector shall verify that the installation meets requirements by measuring the DC resistance of the non-invasive sensor assembly with a properly calibrated ohm meter. 9-10 1257

(e) The measured DC resistance shall be the sum of 1.5 ohms per probe, 3.0 ohms per 100 ft. of lead in wire and 2.0 ohms per 100 ft. of home-run cable and shall be within ± 2% of the calculated DC resistance. (f) The installer of the non-invasive sensor assembly, home-run cable and detector shall measure the change in inductance of the installed noninvasive sensor assembly using a properly designed, matched vehicle detector when a standard, midsize vehicle is driven directly over the sensor. (g) The measured change in inductance for a standard midsize vehicle shall be in the range from 120nH to 1200nH. (h) The installer of the Non-invasive Micro loop assembly, home-run cable and detector shall provide a log of the measured inductance, DC resistance and the change in inductance for each installed non-invasive sensor assembly. 8. Measurement. The Detector Unit and Detector Unit Card will be measured as each unit furnished, installed, made fully operational, and tested in accordance with this Special Specification. The Detector Card Rack will be measured as each unit furnished, installed, made fully operational, and tested in accordance with this Special Specification. The Power Supply will be measured as each unit furnished, installed, made fully operational and tested in accordance with this Special Specification. 9. Payment. The work performed and materials furnished in accordance with this Item and measured as provided under Measurement will be paid for at the unit price bid for Detector Unit, Detector Unit Card, Detector Card Rack (8 Slot) or Power Supply. This price shall be full compensation for all equipment described under this Item with all cables and connectors; all documentation and testing and furnishing all labor, materials, training, and equipment necessary to complete the work. 10-10 1257