Bently Nevada 990-04-50-02-CN two-wire 4-20 mA vibration transmitter, 0-4 mils

Technical Specifications

Main Features and Advantages

One device instead of a proximity driver plus a monitor: The Bently Nevada 990-04-50-02-CN​ integrates the Proximitor sensor conditioning with the 4 to 20 mA conversion stage, so a single two-wire loop from the machine to the control room carries both power and signal. For a plant adding vibration monitoring to an existing pump or fan, that means two conductors rather than a shielded probe cable run back to a rack and a separate analogue output, which is usually the deciding factor when the nearest spare conduit is already full.Sizing that matches small and medium machines: The 0 to 4 mils peak-to-peak full scale of the Bently Nevada 990-04-50-02-CN​ suits machinery with fluid-film or sleeve bearings, where normal running vibration is a small fraction of the alarm limit and a tighter range gives better resolution on the trend. With ±1.5 % of full-scale accuracy and a 5 Hz to 6,000 Hz bandwidth, it captures running-speed vibration, blade-pass and bearing-related components without the cost of a machinery protection rack.Fault behaviour that protects the operator, not just the loop: A probe lead that falls off, a shorted extension cable or a probe driven out of its linear range would otherwise look like a healthy machine at zero vibration. The Not OK / Signal Defeat circuit in the Bently Nevada 990-04-50-02-CN​ drives the output below 3.6 mA within 100 µs, which a configured PLC or DCS reads as an out-of-range low signal rather than as a quiet machine, and the loop recovers within two to three seconds once the fault clears.Diagnostics without a shutdown: The non-isolated PROX OUT coaxial port provides the raw dynamic vibration and gap voltage signal, so a technician can connect a portable analyser or oscilloscope at the panel and capture a waveform or a spectrum during a routine walk-through. Non-interacting zero and span potentiometers allow on-site loop calibration without iteration, and a dedicated test input pin lets the loop be verified with a signal generator without disturbing the probe installation.Built for the environment it is mounted in: The fully potted housing of the Bently Nevada 990-04-50-02-CN​ is rated for 100 % condensing humidity and operates from -35 °C to +85 °C, which covers outdoor pump stations, cooling tower basins and unconditioned compressor enclosures. The bulkhead screw mounting of this variant holds the transmitter rigidly to the enclosure wall, which is preferable to a DIN clip where the panel is subject to machinery vibration or where the cable gland exerts a continuous pull on the housing.