Bently Nevada 990-10-50-01-05 990 Vibration Transmitter

The 990-10-50-01-05 is a two-wire, loop-powered vibration transmitter designed to provide a simple 4 to 20 mA proportional vibration signal directly to a machinery control system. This 990 Vibration Transmitter integrates a Proximitor Sensor into a single unit, accepting input from a 3300 NSv proximity probe and its matching extension cable. It conditions the transducer signal into appropriate peak-to-peak vibration amplitude engineering units, enabling cost-effective machinery protection alarming, logic, and overall vibration trending without requiring an external proximity sensor unit.

Features

• Integrated Proximitor Sensor eliminates the need for an external housing or separate signal conditioner.
• Non-isolated PROX OUT and COM terminals alongside a coaxial connector provide dynamic vibration and gap voltage signal output for diagnostics.
• Non-interacting zero and span potentiometers beneath the transmitter label allow easy loop adjustment.
• Dedicated Test Input pin enables swift verification of the loop signal output via an external function generator.
• Built-in Not OK/Signal Defeat circuit prevents false alarms or high loop outputs caused by loose connections or a faulty proximity probe.
• Dual mounting flexibility with standard options for either 35 mm DIN-rail clips or bulkhead mounting screws.
• Potted construction ensures dependable performance in high-humidity environments up to 100% condensing.

Applications

• Centrifugal air compressors
• Small industrial pumps
• Electric motors
• Industrial cooling fans

Ordering Information

990: Vibration Transmitter

10: 0-10 mils pp (0-250 um pp) Full-scale Option

50: 5.0 meters (16.4 feet) System Length Option

01: 35 mm DIN rail clips Mounting Option

05: CSA Division 2, ATEX Zone 0, ATEX Zone 2 and includes ABS maritime approval Agency Approval Option

Technical Specifications

Connections and Interfaces

Installation Guidelines

Probe Gap Adjustment

The proximity probe must be mechanically gapped between 0.5 and 1.75 mm (20 and 55 mils) from the target surface during installation. This ensures that the probe operates entirely within its linear range and allows the transmitter to accurately generate the full-scale 4 to 20 mA output.

Thread Engagement Limits

When installing the probe into a threaded mounting hole, do not exceed the industry-standard maximum thread engagement length of 1.5 times the nominal thread diameter. For a 1/4-28 thread, maximum engagement is 0.375 in; for M8x1, it is 12 mm. Exceeding these limits can cause mechanical binding and voids the warranty. For 1/4-28 probes, a #3 or larger tap drill is recommended.

Signal Isolation and Diagnostics

The PROX OUT coaxial connector provides a dynamic transducer signal for diagnostics but is not isolated from the 4 to 20 mA loop. While it can connect directly to isolated, battery-powered test equipment, using an external test adapter (such as the 990/991 Test Adapter) is strongly recommended when connecting to AC-powered equipment like oscilloscopes. This preserves loop isolation and prevents false alarms or loop degradation.

Moisture Protection

The transmitter features a potted construction rated for up to 100% condensing humidity. However, the coaxial connectors on the probe and extension cable must be physically protected against fluid ingress to maintain calibration and signal integrity.

Compliance and Certifications

• CSA: Class I, Division 2
• ATEX: Zone 0, Zone 2
• Marine: ABS maritime approval

FAQ

Can the 4 to 20 mA loop output be used to analyze vibration phase or establish gap alarms?

No. The 4 to 20 mA loop output provides only overall peak-to-peak vibration amplitude data. It cannot capture vibration phase or support advanced monitoring features such as gap alarms, phase alarms, Danger Bypass, or Trip Multiply.

What happens to the loop output if the proximity probe cable is disconnected or cut?

The transmitter features a Not OK/Signal Defeat circuit. If a fault or loose connection occurs, the loop signal drops to less than 3.6 mA within 100 microseconds to prevent high outputs or false machinery alarms. It restores within 2 to 3 seconds once the fault condition is resolved.

Is an external Proximitor sensor needed when ordering this transmitter?

No. The unit features a fully integrated Proximitor sensor inside the transmitter housing. It connects directly to the 3300 NSv probe extension cable without needing an intermediary signal conditioner.