## Vibration conversion

## Vibration conversion

(OP)

I am in the electronics repair and calibration field and am required to calibrate vibration (a first for me). The calibration is no problem, but I need to convert the units my engineers gave me in vibration (mV/g) in to what my test equipment reads (mm/s). Does anyone know of a good vibration convertion calculator on the web, or know the conversion constant from mm/s to mV/g?

Thanks,

Bohica

Thanks,

Bohica

## RE: Vibration conversion

Acceleration A = 2 pi f V (pi = 3.14, f = frequency V = velocity

You have mV/g which is a transducer sensivity and need to convert to mm/s. which is velocity, but your sensivity is in acceleration.

If your analysis instrument is a voltage measuring device the easiest way to calibrate it is to use a vibration calibrator (Bruel & Kjaer) which will give a direct 1g rms readout at a particular frequency which is easily converted to velocity since you have all the terms for the equation above.

If you don't have a vibration calibrator, you have to input a known signal such as 1 V rms (sine wave) at say 160 Hertz to your instrument. Assuming that the transducer is accurate in producing say 100 mV/g do the following.

Now 1 V rms = 1000 mV rms then transducer if it produces the same signal will be equal to 1000/100 = 10 g rms acceleration @ 160 Hertz.

10 g rms = 10 x 9.81 = 98.1 m/s2 rms (1g= 9.81 metres per second squared)

Velocity V = A/2*pi*f

= 98.1/(2*3.14*160) = 0.10 m/s rms

0.10 m/s rms x 1.414 = 0.14 m/s peak (peak is convention for vibration velocity)

0.14 m/s peak = 141.42 mm/s peak.

Now just substitute you numbers to calibrate.

## RE: Vibration conversion

I hope this is of help to you.

Take care.

## RE: Vibration conversion

Also be aware that if you are providing a calibration service, you should check the output/response at several different frequencies over the (normal) range of measurement. Most manufacturers provide a certificate of calibration from 0-10 KHz, etc for accelerometers as well as comparison to a NIST reference accelerometer.

## RE: Vibration conversion