Bently Nevada 3500/50M-01-00 288062-02 Tachometer Module

The 3500/50M, full part number 3500/50M-01-00 (incorporating main board spare 288062-02), is a 2-channel hardware module designed within the 3500 Machinery Protection System to process pulse inputs from proximity probe Proximitor sensors or passive magnetic pickups to compute shaft rotative speed, rotor acceleration, or rotor direction. The instrument operates via standard 20 kΩ input impedance circuitry (40 kΩ for TMR architectures) to execute speed monitoring logic, driving dual-level alarm setpoints (Alarm 1 and Alarm 2) with independent, sub-second time delays across user-programmed configurations such as zero speed notification, speed band alarming, and reverse rotation notification. It converts physical rotor events into continuous digital variables, hosting the technical capability to synthesize and supply conditioned Keyphasor signals straight to the 3500 rack backplane for wide-system synchronicity while simultaneously delivering individual +4 to +20 mA proportional recorder currents and unconditioned front-panel coaxial buffered voltages for machine diagnostic investigations.

Ordering Information

• 3500/50M-01-00: Complete Tachometer Module Kit
  • Specifies the combined assembly containing the main front monitor card and the designated internal termination I/O board.
• -01: I/O Module Type Option
  • I/O Module with Internal Terminations.
• -00: Hazardous Area Approval Option
  • No hazardous area agency approvals or certifications required.
• Spares & Accessories
  • Part Number 288062-02: Replacement 3500/50M Tachometer Module Main Board.

Hardware Specifications

Engineering Notes

• Under no circumstances must the 3500/50M module be used independently or as a functional component of an active speed control loop or overspeed protection system, as it lacks the hardware redundancy and execution loop speeds required for emergency machinery trips.
• Passive magnetic pickups must not be specified for zero speed or reverse rotation notification tracking, because they fail to deliver clear wave edge pulses to the detection circuit during low-speed conditions, inducing false direction logic.
• Auto-threshold processing functions down to a minimum trigger amplitude of 1 V peak-to-peak for inputs above 0.0167 Hz, whereas manual threshold choices span +9.5 VDC to -23.5 VDC with a tighter 500 mV peak-to-peak triggering envelope.
• The module features an active peak hold register that captures the highest forward shaft speed, highest reverse speed, and cumulative count of reverse rotations, which are retained until a manual reset command is initiated.

Field Guidelines

• Land the incoming transducer field cabling shields strictly at the internal termination I/O block ground terminal, keeping the outer shield completely ungrounded at the field sensor housing to eliminate electrical noise loops.
• Wire the proportional +4 to +20 mA analog recorder outputs into separate, twisted-shielded instrumentation pairs; short circuits on these auxiliary loops will not disrupt main backplane monitoring functions.
• Verify the physical tooth count profile of the observed target gear wheel matches the event-per-revolution metric programmed in the 3500 Rack Configuration software to prevent scaling multiplication anomalies.
• Route coaxial diagnostic lines to the front-panel buffered outputs through insulated BNC couplings to prevent accidental short-circuit grounding during routine analyzer hookups.

Technical & Procurement FAQ

Q: Can the 3500/50M-01-00 directly replace a dedicated Keyphasor module within a 3500 protection rack?

A: Yes, the 3500/50M can be configured to condition raw speed signals and inject them onto the rack backplane bus as standard Keyphasor pulses, making a separate Keyphasor module unnecessary for adjacent monitors.

Q: Why does the front panel OK LED flash or drop out when utilizing a magnetic pickup at low turbine rotor speeds?

A: Passive magnetic pickups generate voltage amplitudes proportional to speed; if the rotor speed drops below 3.3 Hz, the output voltage drops below the trigger threshold, causing a sensor detection failure.

Q: What is the physical distinction between the 288062-02 part number and the 3500/50M-01-00 catalog designation?

A: The 3500/50M-01-00 is the complete commercial kit number specifying the front card and specific rear I/O board, while 288062-02 is the engineering spare part number for the main front monitor board alone.