ONO SOKKI - Laser Doppler Vibrometer Measurement Range

Measuring range is defined in the scale chart represented by four parameters of frequency, velocity, acceleration and displacement. The Laser Doppler Vibrometer detects velocity of an object. Therefore, the measurable range area is basically represented by two of parameter of velocity expressed in Y-axis and frequency expressed in X-axis. Furthermore, acceleration can be calculated by differential and displacement can obtained by integration.

Suppose that values of velocity and frequency are given, acceleration value can be got by following the line downward to the right from an intersection point of velocity and frequency in the scale chart. And, it can also reach to a displacement value, making trace of the line upward to the right.

An FFT analyzer can easily calculate acceleration and displacement by using its calculation function. Be noted, measuring range of velocity is expressed in half of amplitude of velocity.

Illustration (Measurement Range Example)

(Example)

This is an example of measurement of vibration on an object using the LV-series laser vibrometer.

Velocity : 10mm/s (converted from voltage)
Frequency : 1 kHz (calculated by FFT analyzer)

These two parameters are within the measurable range area rather than measuring range.

Acceleration value can be obtained by conversion and is be approx. 63m/s². (approx. 6.4G) (Acceleration velocity x 2 πf)

And, displacement is approx. 1.6 μm. (Displacement velocity/2 πf)

Both value is expressed in half of amplitude.