Vibration Meter Reading

[tester2]

I am in the electronic repair and calibration field, I required to calibrate a vibration meter(3 axial geophone) The calibration is no problem,but I need to convert the units my manager gave me in Vibration mm/s into what my test instrument reads (Voltmeter(mV))
I am using B&K Accelerometer Type 4382 & Charge Amplifier Type 2635. My 3625 Amplifier Setting as follows:
Transducer Sens: 3.21; 1-11 pC/m/s2,10mV/Unit Out
0.2 Acc Lower Freq Limit,
30KHz Upper Freq Limit.

The Amplifier is Connect to the Voltmeter (mV RMS)
Mounted on the Shaker (labworks Duebase Model db-139/140)
Input Freq @ 20Hz - Voltmeter Read Vibration Meter(mm/s)
9.95mV 10.2
8.97mV 9.2
7.98mV 8.1
6.95mV 7.1
6.0mV 6.0
5.0mV 5.1
4.0mV 4.0
3.0mV 3.0
2.0mV 2.0
1.0mV 1.0

Input Freq 80Hz 2.5mV 0.7 mm/s
5.0mV 1.3 mm/s
6.0mV 1.5 mm/s
7.0mV 1.7 mm/s
8.0mV 1.9 mm/s
9.0mV 2.3 mm/s
10.0mV 2.5 mm/s
15.0mV 3.8 mm/s
20.0mV 5.1 mm/s
25.0mV 6.4 mm/s
30.0mV 7.7 mm/s

How to correlate the reading?
Thanks

Peter

 

[GregLocock]

This is a bit confusing, my guess is that you want to know how to convert from acceleration to velocity.

The 2635 can do that, the knob on the right at the bottom allows you to select between accelelration, velocity and displacement. However the sacling is a bit weird, it is worth experiementing with it, I think it uses units of 10 mm/s.

The other option is to scale your 80 Hz figures, 4 times the frequency should give a factor of 4 difference between acceleration and velocity.

If that doesn't answer your question you need to explain a bit more.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[tester2]

Thank Greglocock,

My manager just me the formula for the calculation.
V = a/2*pi*f
S =V/2*pi*f

V= Velocity,
a= Acceleration
S= Displacement
f= frequency

If I need to measure Velocity - need to turn the dial knob to 1 or 10 Vel.Lower Freq Limit
For Acceleration dial knob set to 0.2 or 2 Acc.Lower Freq Limit.

Best Regards
Peter

 

[GregLocock]

Is that an answer or a question?

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.