Acceleration Pickup Frequently Asked Questions

The measurement of "vibration level" needs to be done with a "vibration level meter." The vibration level refers to the vibration signal corrected for human vibration perception (after frequency correction, leveling <obtaining the effective value>), and it calculates how many times that value is compared to 10 ⁻⁵ m/s ², and displays the logarithm of that value. The electrical configuration is the same as that of a sound level meter, so please refer to the "VR-6100 Vibration Level Meter" for details. The leveled measurement without frequency correction is referred to as the "vibration acceleration level."

This time, since frequency correction cannot be performed, I will explain the method for converting to vibration acceleration level equivalents. However, this method does not include the leveling process defined by JIS, so please treat the results as reference values only.

<Calculation example>

For example, if the voltage value is 1.39 mV (P-P), when converted to 0-P, it becomes,

P-P = 1.39 mV ÷ 2 = 0.695 mV （V_0-P）

When converting voltage to vibration acceleration B m/s ²​

B = 0.695 ÷ A （ m/s²）

The sensitivity of A = NP-3120 is mV/(m/s ²). If we set this to 1.00 mV, then,

B = 0．695／1 m/s² = 0.695 （ m/s² _0−P）

When converting this to the effective value C,

C = B／√2 = 0.695／√2 = 0.491 （ m/s² rms）

To convert this to vibration acceleration level D, take the logarithm of the ratio to 10 ⁻⁵ m/s ².

D = 20 Log （0．491／10⁻⁵） = 20 Log （0.491） + 100= 93.8 dB

This means that (since time waveforms are composed of various frequencies, frequency correction cannot be performed, and they cannot be expressed in terms of vibration levels).

That's correct. Please calculate the sensitivity of A in the above <calculation example> as 10 times ( = 10.0 mV ).