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Concept4 min1 of 1 in the seriesVibration monitoring

Where we areFirst page. Start with the one you can see.

How far the ground moved.

x · mm

Displacement is how far the ground has moved from rest. We write it x and measure it in millimetres.

0.10 mmDisplacement

0 mm/sVelocity

0.16 gAcceleration

t = 13 ms of 100 ms80× slower than real time
  1. 1
    Your call first

    A blast you can feel next door moves the ground about how far?

    Tap one, then watch.

    The distance from rest

    Watch the ruler. It reads the gap between the particle and rest. At the end of the swing it reads 0.10 mm, about the thickness of a sheet of paper.

  2. 2

    It always comes back

    The particle never stays out there. It slides back through rest and out the other side. That round trip is one .

  3. 3

    Tiny, even up close

    A real blast moves the ground next door by less than 1 mm, thinner than a coin. That is why no is written in millimetres.

The relation

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

  1. Displacement0.10 mm

  2. × 2πf at 20 Hz0.10 mm × 126 = 13 mm/s

    Velocity13 mm/s

  3. × 2πf at 20 Hz13 mm/s × 126 = 0.16 g

    Acceleration0.16 g
The general rule

v = 2πf · x, a = 2πf · v

The general rule: a pure tone of size X at frequency f. Speed and push are this, each multiplied by 2πf.
In the field

Would this pass?

A ShotTrack works out displacement from what it senses. The report lists peak displacement in millimetres beside .

Expect a fraction of a millimetre. A number that looks like centimetres means something else is being measured.

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.

Quick check

Check yourself

  1. Is displacement the same as the ground settling?

  2. Where is displacement biggest?

  3. Why are limits not written in millimetres?

0.10 mmDisplacement

0 mm/sVelocity

0.16 gAcceleration

Read next

Next step

Set up a ViB for a blast
Glossary3 min

Blast 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.

Start
Guide8 min

Setting 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
Tool2 min

Vibration calculator

Estimate PPV, acceleration, safe distance and maximum charge from the scaled-distance law.

Open the calculator

Learn →