Section 1 - Operating Information
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1. Operating Information
1.1 Application
Velocity sensors measure machinery casing vibration and are used on machines
where using eddy current proximity transducers are not practical. Typical
applications include pumps, electric motors, compressors, and fans.
The 330525 Velomitor® XA Sensor is designed for applications where a
transducer housing is either unnecessary or not desired.
The 330530 Radiation-Resistant Velomitor® Sensor is designed for applications
requiring a resistance to the effects of gamma-radiation.
Application Alert:
Casing measurements may not be appropriate for
some machinery protection applications.
If you measure the velocity of casing vibration to protect machinery, evaluate the
usefulness of the measurement for each application. Most common machine
malfunctions, such as unbalance or misalignment, occur on the rotor and
originate as an increase (or at least a change) in rotor vibration. In order for any
casing measurement alone to be effective for overall machine protection, the
machine must faithfully transmit a significant amount of rotor vibration to the
machine casing or mounting location of the sensor.
Exercise care when physical installing of the sensor on the bearing housing or
machine casing. Section 2 tells how to install the sensor.
Application Alert:
Improper installation may result in a decrease in the
velocity sensor's amplitude and frequency response and/or generate
false signals that do not represent actual vibration.
1.2 Principle of Operation
The Velomitor® Sensor is a piezoelectric velocity sensor. The sensing element of
the device is a piezoelectric ceramic shear-mode element and electronics. When
subjected to machinery vibration, this system exerts a force on the piezoelectric
ceramic, which generates a signal proportional to that force. The sensor
internally amplifies and integrates this signal to produce a low-noise output signal
that is proportional to velocity.
Application Advisory:
A sudden mechanical impulse may cause the
piezoelectric velocity sensor to generate a low frequency signal that
does not represent actual machinery vibration. This signal may change
the state of alarm and/or danger relays.
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