Description

Application Scenarios

An OEM packager of centrifugal air compressors with fluid-film thrust bearings faced a recurring engineering conflict: the machinery control system needed a simple, deterministic 4–20 mA thrust signal for alarming and trip logic, but the available panel space could not accommodate a separate Proximitor® monitor rack plus field-wiring terminations. Deploying the Bently Nevada 991-10-XX-02-00 collapsed the probe-driver and signal-conditioning function into a single DIN-rail/bulkhead-mounted enclosure — one coaxial connection to the 3300 NSv probe, one 2-wire loop out to the PLC, and no external Proximitor unit required. The 991-10-XX-02-00 is the workhorse in exactly this class of application: OEM compressor packages, small pumps, motors, and fans where a compact, self-contained thrust monitoring loop must deliver actionable data to a machinery control system without the cost and complexity of a full monitor rack.instrumart.com+1

Parameter

Main Parameters	Value / Description
Product Model	Bently Nevada 991-10-XX-02-00 (MOD 163930-01)
Manufacturer	Bently Nevada (Baker Hughes)
Product Category	Thrust (Axial Position) Transmitter
Measured Variable	Shaft axial position / thrust displacement
Full-Scale Range	0–10 mils (0–250 µm), 4–20 mA proportional
Sensor Input	1 × 3300 NSv proximity probe + extension cable (5 m or 7 m)
Power Supply	+12 to +35 Vdc at transmitter terminal, 2-wire loop
Loop Accuracy	±1.5% of full scale (typical)
Maximum Loop Resistance	1000 Ω (including cable) at 35 Vdc
Not OK / Signal Defeat	Output < 3.6 mA within 100 µs of fault; recovery within 0.1 s
Prox Out Scale Factor	7.87 mV/µm (200 mV/mil) ± 6.5%, BNC diagnostic output
Operating Temperature	−35 °C to +85 °C (transmitter); −35 °C to +177 °C (probe)
Humidity / Construction	100% condensing non-submerged; fully potted enclosure
Mounting	Bulkhead screw (option 02) or DIN-rail clip
Weight	0.43 kg (transmitter); ≈ 0.82 kg total system
Approvals	CSA/NRTL/C, ATEX, IECEx, KCs, ABS Type Approval, CE

instrumart.com+2

Technical Principles and Innovative Values

Innovation Point 1 — Integrated Proximitor® Architecture: The 991-10-XX-02-00 embeds the Proximitor® driver electronics inside the transmitter housing, eliminating the external Proximitor unit that conventional proximity-probe installations require. Compared with a discrete probe + Proximitor + monitor architecture, this reduces panel footprint, point-to-point wiring, and commissioning labor on every thrust monitoring point — a structural advantage for OEM packagers standardizing on a single compact loop per machine.apterauto.com
Innovation Point 2 — Not OK/Signal Defeat Circuit: Within 100 µs of a probe fault, loose connection, or electrical degradation, the 991-10-XX-02-00 drives its 4–20 mA output below 3.6 mA, forcing downstream PLCs and machinery control systems into a defined fault state rather than accepting an ambiguous reading. This is a decisive differentiator against generic loop-powered transmitters that continue transmitting a plausible-looking value through an undetected sensor failure — a behavior that directly protects against false-negative machinery protection outcomes.apterauto.com
Innovation Point 3 — Power-up Inhibit and Non-Interacting Calibration: A power-up inhibit circuit suppresses signal errors caused by supply-line voltage transients, while non-interacting zero and span potentiometers mounted beneath the transmitter label allow calibration without iterative adjustment loops. Compared with competitive thrust transmitters that require repeated zero/span correction passes, the 991-10-XX-02-00 shortens loop setup and improves repeatability during field recalibration.apterauto.com
Innovation Point 4 — Potted, Conformal-Proof Construction: Fully potted electronics allow the 991-10-XX-02-00 to tolerate 100% condensing humidity without connector degradation or internal corrosion, extending service life in offshore, tropical, and washdown-prone compressor-house environments where competing open-construction transmitters typically require protective enclosures or earlier replacement.apterauto.com
Innovation Point 5 — Dual-Output Signal Path: Alongside the 4–20 mA loop, the 991-10-XX-02-00 exposes a coaxial PROX OUT connector carrying the raw dynamic gap-voltage signal at 7.87 mV/µm — letting diagnosticians connect a battery-powered analyzer directly for machinery health trending while the 4–20 mA protection loop remains live, something single-output thrust transmitters cannot accommodate without interrupting the protection signal.apterauto.com