
Rotating machinery failures rarely announce themselves — they build quietly through undetected vibration shifts and axial drift until a bearing seizes or a shaft overloads. The Bently Nevada 990 Vibration Transmitter and 991 Thrust Transmitter series exist to catch those signals early, converting mechanical motion data into standardized 4–20 mA outputs that feed directly into protection and monitoring systems.
Amikon stocks both series, including discontinued and hard-to-find part numbers, to keep your equipment running without waiting on slow procurement cycles.
The 990 series converts raw vibration signals from rotating machinery into standardized 4–20 mA transmitter outputs compatible with DCS, PLC, and dedicated protection systems. It measures peak-to-peak vibration amplitude — the measurement direction (radial or axial) is determined by probe mounting orientation, not the transmitter itself.
Designed primarily for OEM applications on smaller rotating equipment, the 990 series is well-suited for:
For large turbines or heavy-duty machinery requiring phase measurement, alarm event waveform capture, or trip multiply functions, a dedicated machinery protection system such as the Bently Nevada 3500 series is the appropriate choice.
Models like 990-05-70-01-CN, 990-10-50-01-01, and 990-04-07-01-05 represent the range of configurations available, from standard builds to MOD variants such as 990-08-xx-01-00 MOD 283278-01.
The 991 series tracks shaft axial position — measuring how far a shaft has displaced along its rotational axis and feeding that data as a real-time 4–20 mA signal into protection and trip systems. Thrust bearing condition is inferred from changes in this axial position over time, providing early warning before displacement reaches damaging thresholds.
Available configurations include 991-25-70-01-00, 991-06-70-02-00, and 991-25-70-03-05, alongside MOD variants like 991-01-xx-01-00 MOD 288865-01.
Many models across both series have been discontinued, yet they remain installed across industrial facilities worldwide. Replacing an entire monitoring system is rarely practical — the downtime, cost, and revalidation effort are too high.
Amikon maintains inventory across both active and discontinued part numbers, enabling like-for-like replacements that preserve existing system architecture and avoid costly requalification.
Yes, both series output standard 4–20 mA signals for direct integration with DCS, PLC, and machinery protection platforms. When connected to a PLC, output is limited to peak-to-peak amplitude trending; phase measurement and alarm event capture require a dedicated protection system.
The 990 series measures peak-to-peak vibration amplitude; the 991 series measures shaft axial position, from which thrust bearing condition is inferred. Both are commonly deployed together for complete rotating machinery protection.
Yes. MOD variants carry factory-applied modifications affecting output range, cable configuration, or mounting. Always match the full part number, including the MOD suffix, to maintain system compatibility.

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