Where we areLast page: the push. This page: how often it all repeats.
How often it repeats.
f · Hz
Frequency is how many times a second the ground completes a . We write it f and measure it in .
Turn the dial. The travel stays the same while speed and push grow.
- 1Your call first
Same travel, twice as often. The top speed…
Tap one, then watch.
Same travel, more often
Hold the travel fixed and turn the dial up. The particle makes the same trip more often, so it must move faster.
- 2
Speed doubles, push quadruples
Each step up the ladder multiplies by the same number, 126 at 20 Hz. That is about the beats per minute of a fast run. Double the frequency and speed doubles; the push goes up four times.
- 3
That is why limits move
A set in g is a different mm/s at every frequency. That is why most draw a that moves with frequency.
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?
A report quotes the beside PPV: the main rhythm in the record. Ground next door usually sits at 5 to 20 Hz, like a slow drum roll.
Read a g trigger at the lowest frequency you expect. That is where a fixed g needs the most speed to fire.
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 dominant frequency the same as sample rate?
Double the frequency, same travel. The peak push…
Why do limits change with frequency?
Next step
Read a real record
A real blast is many tones at once, so the trace is messy. The pure tone is the building block, so you can check the sums.
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