Description

The Bently Nevada 990-05-50-03-05 is a loop-powered, 2-wire machinery protection transmitter. It combines the functionality of a Proximitor sensor and a signal conditioner into a single potted housing, accepting inputs from a 3300 NSv proximity probe to output an industry-standard 4-20 mA signal directly to a PLC or DCS network.

Suffix Breakdown & Model Matrix

• 990: Core product identifier for the 2-wire loop-powered vibration transmitter.
• 05: Full-scale measurement range option specifying 0-5 mils peak-to-peak ($0-125\ \mu\text{m}$ peak-to-peak) relative radial vibration.
• 50: Tuned system length option requiring a 5.0 meter (16.4 feet) total proximity transducer hardware configuration.
• 03: Mounting hardware configuration providing both 35 mm DIN rail clips and bulkhead mounting screws.
• 05: Multi-agency hazardous area approval option including CSA Class I, Div 2, ATEX Zone 0, ATEX Zone 2, and ABS maritime certification.

Hardware Specifications

Signal Conditioning and Diagnostics

Consequently, the 990-05-50-03-05 hardware executes immediate signal conditioning, translating rapid high-frequency shaft transitions into a stable current loop telemetry stream. During standard machinery runout, it generates an RF eddy-current field via the connected 3300 NSv probe, requiring a physical probe gap baseline between 0.5 mm and 1.75 mm.

Meanwhile, it provides a dedicated, non-isolated PROX OUT coaxial connector on the casing faceplate. This test point outputs the raw dynamic vibration data and steady-state DC gap voltage for handheld collectors. Furthermore, the internal electronics enforce rigorous cross-talk suppression alongside an automatic Power-up Inhibit filter, absorbing transient voltage spikes during startup loops to lock out false alarms.

Frequently Asked Questions

Q: How does the “Not OK / Signal Defeat” safety loop behave if the 3300 NSv probe cable is accidentally severed?

A: When a sensor line break, short-circuit, or severe tracking fault occurs, the internal safety logic automatically triggers. Within 100 microseconds, it clamps the loop current to less than 3.6 mA, alerting the control room DCS of a hardware malfunction rather than initiating an unneeded machine shutdown.

Q: Can an operator plug an AC-powered oscilloscope directly into the PROX OUT port to look at shaft orbits?

A: No, because the PROX OUT and COM ports share a non-isolated baseline ground with the 4-20 mA loop power circuit. Connecting an AC-powered oscilloscope directly can create an unintended ground path, corrupting the loop. Technicians should use a 990/991 Test Adapter (Part Number 122115-01) to isolate and invert the signal safely.

Field Installation Guidelines

• Chassis Installation: First, determine whether bulkhead or rail mounting offers the best layout. Secure the assembly cleanly to a low-vibration structural column or junction box panel; tight integration suppresses parasitic casing vibration from introducing signal artifacts.
• Transducer Shielding: Terminate the extension cable outer shield drain wire strictly at the transmitter shield terminal base. Conversely, do not terminate the shield on the machinery casing side, as single-point grounding is mandatory to prevent stray electromagnetic currents from riding the instrumentation loop.
• Wiring Routing: Separate the twisted, shielded 4-20 mA signal wiring from primary heavy-current three-phase AC distribution leads. Furthermore, utilize grounded metallic conduits to avoid inductive noise coupling from neighboring motors and variable frequency drives (VFDs).