The Rion VM-54
Whole Body Vibration program are ideal for evaluating railway vibration. The system directly measures and logs Vibration Dose Values with all the current applicable weightings (user selectable). It's as simple as leaving a sound level meter out for a long-term survey. With the data stored to compact flash in the form of a comma separated variable text file you can open it directly into excel via a card reader.
The standard way of doing an environmental railway vibration assessment is to use the Rion VM-54 and VX-54WB1 with a Rion PV-83CW. This gives overall weighted acceleration levels between 0.5 and 80 Hz. There are several options for looking at the vibration levels in more detail or over a more extended frequency range.
There is an FFT program available for the VM-54. This is typically used to measure the frequency content of sample train passbys. However, it should be noted that with the standard ground vibration tri-axial accelerometer (the PC-83CW) the frequency range is limited to 0.5 80 Hz. A good choice for a wider frequency range is to use three PV-87 high-sensitivity, full-range accelerometers via a Rion VP-80 3 channel charge amp. This enables the full frequency range of the VM-54 FFT option (up to 1000 Hz) to be used.
If you prefer to store the waveform of the passby for post-processing there are a few options available. You can take the output from the VM-54 and record it using a DA-20 which stores multi-channel wav files (up to 4 channels). In addition to the DA-20 Viewer Software that is provided with the DA-20, we can provide Prosig DATs Lite (developed with Prosig especially for use with Rion instruments) and CATWAVE. However, you need to be aware that if you are using the VX-54WB1 Whole Body Vibration program the outputs of the VM-54 will be subject to the weightings you have selected (or the band-limiting curves set out in ISO 8041 if you switch the weightings off) so if you want the completely raw vibration data you will have to unload the VX-54WB1 program from the VM-54 (which only takes a matter of seconds).
The advantage of using the VM-54 as a 'front end' to a data recorder is that you do get to see the acceleration levels in real time on site.
An alternative to using the outputs of the VM-54 to plug into the inputs of a DA-20 or DA-40 for recording the raw waveforms as mult-channel wav files is to use up to 3 charge accelerometers with the DA-20 (via the VP-80 3 channel charge amp), up to 4 CCLD accelerometers directly into the DA-20 or up to 8 CCLD accelerometers directly into the DA-40.