Definitions, Terms, Units and Parameters
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Vector: is a
quantityhaving both magnitude and direction, for example acceleration, force and velocity.
As opposed to scalar quantities like density, mass and speed which have magnitude but no direction.
Vectors can only be added, subtracted or multiplied using mathematical procedures that take account of the co-ordinates. A vector is defined as an element of a vector space.
Vector space: vector spaces are applied throughout mathematics, science and engineering. They are the linear-algebraic notion to deal with systems of linear equations; offer a framework for Fourier expansion or provide an environment that can be used for solution techniques for partial differential equations.
Velocity : v: the rate of change of position and is a vector quantity as both speed and direction are required to define it.
The SI units are metres per second: (m/s).
v = u + at where v = velocity, u = start velocity, a = acceleration in m/s2 and t = time.
In the field of vibration acceleration a, velocity v, displacement s and angular frequency ω are related. - for example v = a/ω, s = v/ω, where ω = 2·π·f
It follows that 10 m/s2 = 0.01 m/s = 10 μm at 159 Hz
This works for all frequencies, we just chose 159 Hz to keep the numbers simple. We also have a vibration nomogram for downloading.
See also Particle Velocity, used in acoustic wave theory and Angular Velocity.
See also the Standard Reference Levels table
Velocity of Soundis usually taken to mean the speed of sound.
Should not be confused with sound particle velocity, which is the velocity of the individual particles. To add to the confusion the unit v is often included.
Vibration: mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random.
Vibration is commonly expressed in terms of Acceleration, Velocity, Displacement and Frequency which are related.
See also the table of decibel reference levels.
Vibration at Work Regulations: The Control of Vibration at Work Regulations 2005 (the Vibration Regulations), came into force on 6 July 2005 and aim to protect workers from risks to health from vibration.
The regulations introduce action and limit values for hand arm and whole body vibration.
For others details see the Government and/or HSE websites.
see also the acceleration equivalent value : Aeq and hand arm vibration syndrome : HAVS and whole body vibration - WBV
Vibration Parameters :The main vibration parameters are Acceleration, Velocity, Displacement. Click a link to see details and sub-parameters if that's a good word
Vibration Reference Levels
Vibration Reference Level - acceleration = 10 micro-m/s2 (10 µm/s2)
Vibration Reference Level - velocity = 1 x 10-8 m/s
Vibration Regulations :see Vibration at Work Regulations above
Vibration Velocity Level : Lv: = 20 lg(v/vo) dB re 10-8 m/s = 10-6 cm/s
* Velocity Reference Level = 1 x 10-8 m/s
an increase or decrease in velocity of 20 dB = a factor of 10
a 40 dB = a factor of 100
a 60 dB = a factor of 1000 ... etc.,
See also the table of other Standard Reference Levels
Volt : V: the derived SI unit of electric potential; the potential difference between two points on a conductor carrying a current of 1 ampere, when the power dissipated between these points is 1 watt
Voltage Level : LV: dB(1 VRMS) : voltage relative to 1 volt, regardless of impedance.
Lv = 20 lg (V/Vo) dBV
Reference voltage Vo = 1 volt = 0 dB
Volume : V: the SI unit is the cubic metre : m3
Volumetric Flow: also known as volume flow rate or rate of fluid flow is the volume of fluid which passes through a given surface per unit time, the units are - m3/s
Volumetric Power Density: volume based power density - watt/m3
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