How to select Vibration range

[Arulkumar P]

I have to measure bearing block vibration by using loop powered transmitter.
Rotating speed of the bearing block is around 300 to 400 rpm of continious opration.
I choose meritx vibration transmitter model no: ST 5484E.
In this model they offer scale range of peak(pk) and rms value.
Kindly advise wether i can select pk or rms value.
Which range is suitable for my application.

 

[electricpete]

1 - RMS is what ISO recommends for an overall value.

2 - In the U.S., overall vibration velocity is often expressed as "peak" which is simply sqrt(2) times the rms value.

3 - Then there is "true peak", which the highest magnitude obtained. To add confusion, some people (even ISO I think) call this peak. Crest factor = true peak / rms.

Clear as mud?

I'm not exactly clear whether meritx meant #2 or #3 for peak. And I'm not exactly clear what type of bearing (sleeve or anti-friction), what type of machine and why you're monitoring it. So I can't begin to answer the question.


=====================================
(2B)+(2B)' ?

 

[Arulkumar P]

M/s Metrix is a US company,which is make vibration switch,transmitter.
2. Ball bearing vibration we have to measure.
3.Aircooler application which is in refinery plant.
4. In air cooler arrangement, bearing block top ends connected in axial flow fans. Bottom side connected in belt pulley arrangement to couple with motor. This entire assembly supported in steel structure.
I hope you understand the application.

 

[electricpete]

I'm not exactly clear whether meritx meant #2 or #3 for peak.

A little googling clears up there is no true peak in sight, only what they call a "derived peak", which is simply the rms times sqrt(2)

http://www.metrixvibration.com/docs/1004457-ST5484E-Vibration-Transmitter-DS.pdf

RMS Amplitude Detection – Measures Root
Mean Square (RMS) vibration amplitude.  
Options available for True RMS or scaled
RMS (RMS x √2) for “derived peak.”

So the output will not carry any different information, just a scaling factor which should be considered by those who read the device.

In the US if reading bearing housing vibration in inches per second, I would select the peak option because that is consistent with what most of the vibration analysts use.

Overseas if reading bearing housing vibration in mm per second, I would select the rms option because that is consistent with what most of the vibration analysts use.

The standard model only comes with inches per second (which points me in the direction of peak, unless you have the special model with mm/sec). You might also talk to your vib analyst to see which he prefers.




=====================================
(2B)+(2B)' ?