Measuring reference signal of magnetic excitation (a solenoid)

[ricky24]

Hello all,

I am now preparing an experiment based on the ASTM E756 damping test to study the properties of some VEM bought. In the test non-contact exciter is used to excite a sandwiched beam. I used a solenoid and is able to excite the beam with both sinusoidal and random signals. But now I am having trouble to measure the reference signal of the solenoid, which is used to create a frequency response function. What quantity should I measure, current, magnetic field or other? What device(s) should be used?

I tried to use a speaker (with a microphone to measure the reference signal) to excite the beam. But I was not able to excite high frequency modes (>1000 Hz).

Thanks.

Ricky

 

[MikeyP]

If you suspend the solenoid freely, you can mount an accelerometer on it and use Newton II and III to get an estimate of the force applied to the beam. Bear in mind that the applied force will be proportional to the square of the coil current so you can't use the input voltage or current as a reference.

M

--
Dr Michael F Platten

 

[tomirvine]

You could also excite the beam with an impulse hammer, with a built-in force transducer. These hammers typically have interchangeable tips to control the duration and hence the frequency of the input pulse.

Then measure the response of the beam with an accelerometer.

Damping can then be calculated from the resulting signals either in the time domain or the the frequency domain.

Tom Irvine

http://www.vibrationdata.com