Hi all,

I recently faced a case in collecting vibration data from a pump using a CSI handheld general purpose accelerometer. The vibration amplitude varied from 0.1 to 0.3 rms and this is not a beating problem.

The amplitude change is related to the stress imposed by the hand holding the accelerometer which was observed using monitor modes of both overall vibration and spectrum. This case reminded me with some charts in the training literature where the sensor mounting frequency can be excited if there is a frequency from the machine matching this mounting frequency. The spectrum shows two main frequencies at about 55000 and 66000 cpm and the general rule of thumb states that the handheld accelerometers are excited at this range of frequency. I tested three sensor (of the same design) and they gave same results.

I want to have another opinion to verify my doubt. I wonder if anybody encountered such a case before.

Thanks- Ali M. Al-Shurafa

http://www.designinfo.com/wilcoxon/ref/AccelInstall.html

Read this Ali. It may help you understand your application.

Ron.

The best way to be sure would be to repeat the measurement with either s magnet-mounted accelerometer on a smooth, flat, paint-free surface or using a stud-mount accelerometer. If the peaks drop in level, it's a pretty strong indication that the levels are affected by mounting resonance.

Jon
Spintelligent Labs

Thanks for your reply. I checked the article and it contains similar for the mounting effect info as another article called: "PROPER SELECTION AND INSTALLATION OF INDUSTRIAL ACCELEROMETERS", from which I'm attaching the graph below.

Actually I'm looking for actual experience with the commonly used CSI general purpose accelerometers.

Regarding the stud and magnet mounting, they are not possible due to unavailability of an access and that the casing is not ferrous material.

Thx- Ali M. Al-Shurafa