THE vibration monitoring unit (VMU) from Thermo Fisher Scientific is a compact system designed to measure overall vibration on industrial plant, including pumps, and to interface to industrial process monitoring and control equipment.
The VMU provides a 4-20mA loop output, proportional to vibration velocity or displacement, as selected by a switch on the circuit card, and an adjustable alarm output (relay contact) which may be set to warn the operator when vibration levels exceed a preset percentage of the full scale range.
An ac monitor output is provided on a card for vibration signal analysis.
The operating mode may be switched between a velocity range of 0-25mm/sec rms and a displacement range of 0-0.4mm rms. Range and frequency bandwidth are all field adjustable.
The monitor output may be switched between the velocity/displacement signal, as set by the operating mode, or the input acceleration signal.
The alarm output trip point can be adjusted from 10% to 100% of the selected full scale range. The alarm output is provided by Normally Open relay contacts, electrically isolated from the rest of the circuit.
The relay contacts will close within approximately 10 seconds of the vibration level continuously exceeding the preset level. The relay will open after 3-5 seconds if the vibration level falls back below the preset level.
Vibration is sensed by a high sensitivity, low impedance quartz accelerometer. The accelerometer may be mounted within the VMU enclosure to provide a single compact system, or remote from the VMU where more severe environments exist at the measurement site.
The unit is powered from a nominal 24V dc, supplied from the monitoring system. Various options are available to suit different applications.