2-3 hz measurement

[Sofistioelevib]

This is strange request,
What do you will use to acquire 2-3 Hz?
Other than specific sensors(seismic) there are particular techniques using normal 100 or 500 mv/g or normal velocity sensors?

 

[GregLocock]

For frequencies below 4 Hz I used to use strain gauge accelerometers, as they work down to DC. Velocity sensors would be good, and I dare say various laser based instruments will work.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Strong]

Both 100-mv/g and 500-mv/g ICP/IEPE accelerometers have rated frequency response well below 2-Hz (for example CTC). Obviously the more sensitive one produces 5x higher voltage for the same acceleration level (g), and it generally would be a better choice. Some measurement issues include noise floor (spectrum), background vibrations (spectrum), cable vibrations, HP filter setting of analyzer, signal integration for velocity/displacement (may not be possible). Another type of low frequency accelerometer is the MEMS that also has DC response, but check the sensitivity and noise floor specifications as compared to the ICP/IEPE type. I have also used a proximity probe, LVDT and lanyard potentiometer, and geophone sensors for special low frequency measurements. What are you trying to measure?

Walt

 

[Sofistioelevib]

@Greglocock
@Strong
Thank you for answers, i'm going to use the proximity probe because for my measurements i need a flat response in that spectrum region.

@Strong
Substantially i'm going to measure the resonant frequency for a vibration absorber under record player. The problem is to evaluate the resonance amplitude during an impact test (suppose a car or truch passing near the record player)

Regards

 

[Strong]

Avoid using a standard size 100-mv or 500-mv accelerometer, since its weight/mass could affect the NF you are trying to measure. Good luck with a proximity probe, since the metal target (if added) may be too heavy. You might consider measuring the floor vibration and on top of shelf/cabinet that supports the record player to capture vibrations from passing trucks. You might also measure the record player output while playing a calibration record, and analyze for test tone amplitude modulation. The vibration isolator under the record player is only part of the structural dynamics.

Walt

 

[Sofistioelevib]

I'll post the measurement and application when done
Thanks guys