Where we areLast page: how far. This page: how fast.
How fast the ground is moving.
v · mm/s
Velocity is how fast the ground is moving at one instant. We write it v and measure it in millimetres per second.
The v arrow shows speed: longest through rest, gone at the ends.
- 1Your call first
The particle is at the far end of its swing. Right now its speed is…
Tap one, then watch.
It stops at the ends
Look at the v arrow. At the end of the swing it shrinks to a dot: the particle has stopped to turn round.
- 2
Fastest through rest
Through rest the arrow is longest. Here the ground moves 13 mm/s, slower than a snail, and still over most limits.
- 3
PPV is the biggest speed
is the biggest speed anywhere in the record, not the speed at one chosen moment. A of 10 mm/s caps that peak, like a speed limit for the ground.
How the four connect
One motion, four numbers. Turn the dial and watch the sums.
0.10 mmDisplacement
13 mm/sVelocity
0.16 gAcceleration · 50 ms per cycle
- Displacement0.10 mm
× 2πf at 20 Hz0.10 mm × 126 = 13 mm/s
Velocity13 mm/s× 2πf at 20 Hz13 mm/s × 126 = 0.16 g
Acceleration0.16 g
The general rule
v = 2πf · x, a = 2πf · v
Would this pass?
Limits are written in . A ViB senses the push; the platform turns it into speed for the report.
The card shows this motion's peak speed against a 10 mm/s limit, like a speed limit for the ground. Move the frequency and watch it pass or fail.
Over the limit
0.10 mmDisplacement
13 mm/sVelocity
0.16 gAcceleration
0.10 mmDisplacement
13 mm/sVelocity
0.16 gAcceleration · 50 ms per cycle
An indicative limit. Your project's standard sets the real one.
Check yourself
Is PPV the speed at one moment?
Where is the ground moving fastest?
Why are limits written in mm/s?
Next step
Acceleration
How fast the velocity is changing. This is what a ViB accelerometer senses.
StartBlast vibration glossary
Every term you will meet on a monitoring job, explained in one sentence first. Tap a term anywhere on the site to see it.
StartSetting a ViB up for a blast
Pick the job, read the numbers it needs, and know what the unit will do when the shot fires.
Start