{"product_id":"bently-nevada-125740-01-tachometer-monitor-i-o-module","title":"Bently Nevada 125740-01 Tachometer Monitor I\/O Module","description":"\u003ch2\u003eBently Nevada 125740-01 Tachometer Monitor I\/O Module\u003c\/h2\u003e\n\u003cp\u003eThe \u003cstrong\u003eBently Nevada 125740-01\u003c\/strong\u003e is the rear Input\/Output (I\/O) module designed for the \u003cstrong\u003e3500\/50 Tachometer Monitor\u003c\/strong\u003e. Located at the back of the 3500 chassis, this module provides the physical terminal interfaces to receive pulses from Keyphasor transducers, proximity probes, or magnetic pickups to measure rotational speed, phase, and acceleration.\u003c\/p\u003e\n\u003ch3\u003eHardware Specifications\u003c\/h3\u003e\n\u003cfigure class=\"table\"\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003e\u003cstrong\u003eParameter\u003c\/strong\u003e\u003c\/th\u003e\n\u003cth\u003e\u003cstrong\u003eSpecification\u003c\/strong\u003e\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePart Number\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e125740-01\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eAssociated Module\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e3500\/50 Tachometer Monitor\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eConnection Style\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eInternal Terminations (Accepts direct wire-to-lug field connections)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eTerminal Capacity\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e0.2 to 1.5 mm² (16 to 24 AWG) multi-strand or solid shielded industrial wire\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eWeight\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e0.36 kg (0.79 lbs) \u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eDimensions\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e240 mm × 25.4 mm × 241 mm (9.45 in × 1.00 in × 9.50 in)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eOperating Temperature\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e-30°C to +65°C (-22°F to +150°F)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePower Consumption\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003ePassive routing and line conditioning (\u0026lt; 1.5 Watts drawn from rack)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eIsolation Strength\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e500 Vrms galvanic isolation between field inputs and the rack backplane\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eRack Allocation\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eInstalls into the upper or lower rear slots directly behind the 3500\/50 main card\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eCompliance\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eFully compliant with API 670 machinery protection standards\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/figure\u003e\n\u003ch3\u003eOperational Functionality\u003c\/h3\u003e\n\u003cp\u003eThe 125740-01 rear I\/O module processes speed-related trigger pulses before routing them to the front-facing 3500\/50 main card. It supports several turbine protection applications:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eStandard Tachometer:\u003c\/strong\u003e Tracks absolute rotor speed (RPM) and rotor acceleration trends.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReverse Rotation Detection:\u003c\/strong\u003e Verifies that the turbine shaft does not spin backwards during shutdown, preventing severe auxiliary pump or seal damage.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eZero Speed Tracking:\u003c\/strong\u003e Safely monitors low-frequency shaft movements down to 0 Hz, validating when a turbine has come to a complete stop before turning gear engagement.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh-Temperature Compatibility:\u003c\/strong\u003e Frequently paired with Bently Nevada’s \u003cstrong\u003e3300 High-Temperature Proximity System (HTPS)\u003c\/strong\u003e. This system routes speed and phase trigger signals out of extreme thermal zones—such as near labyrinth steam seals, turbine exhaust paths, and strut-supported hot bearings—and routes them safely into the 125740-01 terminals.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eGalvanic Protection Shielding:\u003c\/strong\u003e The module incorporates built-in 500 Vrms isolation circuitry. If a high-voltage spike occurs on the field wiring side, the onboard isolation barriers absorb the energy, preventing electrical faults from damaging the expensive internal bus of the 3500 system rack.\u003c\/p\u003e\n\u003c\/blockquote\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Can this I\/O module accept input from both active magnetic pickups and passive proximity sensors?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eA: Yes. The 125740-01 is fully configurable to interface with passive proximity probes (like the 3300 XL series), active magnetic pickups, or optical speed sensors. These parameters are assigned within the 3500 Rack Configuration Software.\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What is the difference between \"Internal Terminations\" and \"External Terminations\"?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eA: \"Internal Terminations\" (like the 125740-01) mean that the field sensor wires land directly onto terminal strips located right on the module's PCB faceplate. \"External Terminations\" route the backplane connections via a multi-pin cable to a separate DIN-rail terminal block mounted elsewhere in the cabinet.\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Does replacing the 125740-01 rear I\/O card require powering down the entire 3500 rack?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eA: No. The rear I\/O modules can be hot-swapped while the rack is powered. However, disconnecting this module will interrupt the active speed monitoring loop. Ensure that any automatic safety trip logic based on speed or Keyphasor data is bypassed or inhibited first.\u003c\/strong\u003e\u003c\/p\u003e\n\u003ch3\u003eField Installation Guidelines\u003c\/h3\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e1.Inhibit overspeed trip relays:\u003c\/strong\u003ePrepare the system.\u003c\/p\u003e\n\u003cp\u003eBefore disconnecting the tachometer connections, place any overspeed or zero-speed safety interlocks linked to this card into \u003cstrong\u003eBypass\u003c\/strong\u003e to prevent an automated system trip.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.Disconnect field wires:\u003c\/strong\u003eClean terminal layout.\u003c\/p\u003e\n\u003cp\u003eLabel and disconnect the individual sensor wires from the green terminal block plug on the card faceplate.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.Remove the old rear I\/O card:\u003c\/strong\u003eUnscrew chassis retainers.\u003c\/p\u003e\n\u003cp\u003eUnscrew the captive screws holding the I\/O card faceplate to the rack frame, then gently pull the card straight out of the slot.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.Insert the new 125740-01 card:\u003c\/strong\u003eAlign guide pins.\u003c\/p\u003e\n\u003cp\u003eSlide the new card into the guide rails at the back of the rack until it seats firmly into the backplane connector. Hand-tighten the captive screws.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003e5.Plug in wire terminal block:\u003c\/strong\u003eRestore sensor connection.\u003c\/p\u003e\n\u003cp\u003eReinsert the wired green terminal blocks into the socket connectors, verify that the \u003cstrong\u003eOK\u003c\/strong\u003e LED on the front 3500\/50 card lights up, and remove the safety bypasses.\u003c\/p\u003e\n\u003cp\u003e\u003cspan style=\"font-size: 14px;\"\u003e\u003cstrong\u003e\u003cspan style=\"color: #e74c3c;\"\u003e\u003cspan style=\"font-size: 20px;\"\u003e\u003cspan style=\"font-family: Arial,Helvetica,sans-serif;\"\u003e\u003cstrong\u003e\u003c\/strong\u003e\u003c\/span\u003e\u003c\/span\u003e\u003c\/span\u003e \u003c\/strong\u003e\u003c\/span\u003e\u003c\/p\u003e","brand":"Bently Nevada","offers":[{"title":"Default Title","offer_id":44356880269411,"sku":null,"price":180.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0549\/2775\/3315\/files\/125740-01-1.jpg?v=1784015042","url":"https:\/\/precisemodule.com\/products\/bently-nevada-125740-01-tachometer-monitor-i-o-module","provider":"Precise Module Ltd.","version":"1.0","type":"link"}