Bently Nevada 990-05-70-02-00 Vibration Transmitter

Description

The Bently Nevada 990-05-70-02-00 is a two-wire, loop-powered 990 Vibration Transmitter designed to process signals from proximity probes into a proportional 4 to 20 mA industry-standard current loop. The device directly interfaces with a 3300 NSv proximity probe and its matching extension cable to monitor peak-to-peak vibration amplitude. This transmitter provides an engineered solution for machinery control systems where local control-level protection alarming and logic are required. It operates as an integrated Proximitor Sensor unit, optimizing signal processing for compact industrial equipment.

Features

• Integrated Proximitor Sensor requires no external driver unit.
• Non-isolated PROX OUT and COM terminals plus a coaxial connector deliver dynamic vibration and gap voltage signals.
• Non-interacting zero and span potentiometers enable straightforward calibration and loop adjustment.
• Test Input pin permits direct verification of the loop output using an external function generator.
• Not OK/Signal Defeat circuit quickly drops output below 3.6 mA to suppress false alarms during probe faults.
• Potted construction provides robust environmental protection for high-humidity installations.
• Compact design supports installation in confined spaces with minimal clearance.

Applications

• Centrifugal air compressors
• Small pumps and fluid machinery
• Industrial electric motors
• Cooling and ventilation fans
• OEM machinery control system integration

Ordering Information

Technical Specifications

Connections and Interfaces

Installation Guidelines

Probe Gap Adjustment

The proximity probe must be physically gapped between 0.5 and 1.75 mm (20 and 55 mils) from the target surface. This ensures the target remains inside the transmitter's linear measurement range during machine operation.

Thread Engagement Limits

Do not exceed the maximum thread engagement lengths during installation to avoid component binding. For 1/4-28 threads, the limit is 0.375 inches; for M8x1 threads, the limit is 12 mm. Bently Nevada does not cover warranty replacements for probes damaged by excessive thread engagement.

Moisture Protection

The unit utilizes potted construction suitable for up to 100% condensing humidity. To maintain loop integrity, all coaxial connectors must be protected against direct moisture ingress using appropriate sealing boots or enclosures.

Signal Isolation and Test Adapters

The PROX OUT coaxial connector is non-isolated from the 4 to 20 mA loop circuit. While compatible with ungrounded, portable test equipment, you must use a 122115-01 or 990/991 Test Adapter when connecting to grounded, ac-powered test equipment like oscilloscopes to isolate the loops and maintain safety integrity.

FAQ

What limitations do vibration transmitters have compared to standard machinery protection monitors?

Transmitters provide peak-to-peak trending data only and cannot capture dynamic waveforms during an alarm event. They do not support phase tracking, gap alarms, Timed OK channel defeat, Danger Bypass, or Trip Multiply, and they cannot interface with plant-wide diagnostic platforms like System 1.

How does the Not OK circuit manage loose sensor connections?

If a probe connection loosens or fails, the transmitter drops the loop output below 3.6 mA within 100 microseconds. Once the connection is secure, the transmitter waits 2 to 3 seconds before restoring the standard output signal.

What size target is required for the transmitter to meet its accuracy specification?

The target must have a minimum diameter of 9.5 mm (0.375 inches) and be composed of AISI 4140 steel to maintain the calibrated scale factor.