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 Data collection time is
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Shurafa2

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Reply with quote  #1 


Vendor Warning

During a typical vibration data collection, how much time is needed (by the analyzer) to take a reading from a bearing housing of a small motor?

I'm not sure if this is clearly taught in the vibration courses (Category I) or if a person without first-hand experience in data collection can have a feeling of the required time.

Comments are welcome.

This page is from "Data Acquisition" Part 2 of Vibration Analysis Certification Exam Preparation Package. It contains more than 150 practice questions on Data Acquisition for Cat I. Amazon Link: https://www.amazon.com/gp/book...ref=dp_st_1644150093

Regards- Ali M. Al-Shurafa

Vibration Analysis Certification Exam Category I Data Acquisition Ques.png 


fburgos

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Reply with quote  #2 
How slow it is?
Noknroll

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Reply with quote  #3 
The question "how long is a piece of string?" comes to mind
EDIT:
There must be some clue, like motor speed and/or how many revolutions you want to capture
or some AP set parameters
MarkL

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Reply with quote  #4 
I'll add same comment, questions too vague, you need to define a speed and maybe ask along lines of what should be the optimal collection time. From my hazy memory I don't recall learning about collection time much from my level1.
Curran919

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Reply with quote  #5 
Depends if you need to differentiate between 2xLF and 2xn?
Shurafa2

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Reply with quote  #6 
Quote:
Originally Posted by Noknroll
The question "how long is a piece of string?" comes to mind
EDIT:
There must be some clue, like motor speed and/or how many revolutions you want to capture
or some AP set parameters



Well, the question I guess is intended not to give specifics as it asks about the normal range for an analyzer to take typical a reading.

Regards- Ali M. Al-Shurafa
Shurafa2

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Reply with quote  #7 
Quote:
Originally Posted by Curran919
Depends if you need to differentiate between 2xLF and 2xn?


Based on these two cases, how much time is needed for each?

Regards- Ali M. Al-Shurafa
Shurafa2

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Reply with quote  #8 
Quote:
Originally Posted by Noknroll
The question "how long is a piece of string?" comes to mind
EDIT:
There must be some clue, like motor speed and/or how many revolutions you want to capture
or some AP set parameters


Interesting.

I would say it could be analogous to asking how tall is a typical healthy adult:

1.5-2 mm
1.5-2 cm
1.5-2 m
1.5-2 km


Can you take any typical setting you have any see the time? Perhaps your "typical" would not be typical for me.

Regards- Ali M. Al-Shurafa
Shurafa2

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Reply with quote  #9 
Quote:
Originally Posted by MarkL
I'll add same comment, questions too vague, you need to define a speed and maybe ask along lines of what should be the optimal collection time. From my hazy memory I don't recall learning about collection time much from my level1.


Mark, see if these are typical:

Speed: 1000-3000 rpm
Lines: 400-800 lines (corrected 8000)

How long does it take to be captured?

Regards- Ali M. Al-Shurafa
Shurafa2

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Reply with quote  #10 
Quote:
Originally Posted by fburgos
How slow it is?


Say 1000 rpm to 3600 rpm.

Regards- Ali M. Al-Shurafa
MarkL

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Reply with quote  #11 
Quote:
Originally Posted by Shurafa2


Mark, see if these are typical:

Speed: 1000-3000 rpm
Lines: 400-8000 lines

How long does it take to be captured?

Regards- Ali M. Al-Shurafa


Are you asking 1000rpm at 400 lines resolution and 3000 rpm at 8000 lines?
(8000lines is not a multiple)
400
800
1600
3200
6400
12800
Are the common ones I’ve seen.
fburgos

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Reply with quote  #12 
I belive this question is not suitable for any certification test, you have too many variables that afect the time of measurements, averages, overlap, separating frequency, fmax, etc
OLi

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Reply with quote  #13 

And nowadays, 1 axis or 3 axis, it do vary pending how the system do it....... just to make it complicated but IRL it is complicated.....
Number of lines are technically based on a binary number from old days and the algorithm involved so

1024 samples give 400 LOR  as you drop a few bins due to the slope of the antialiasing filter and that may vary today as can be seen in specs
2048 samples give 800 LOR etc. etc.


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Shurafa2

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Reply with quote  #14 
Quote:
Originally Posted by MarkL


Are you asking 1000rpm at 400 lines resolution and 3000 rpm at 8000 lines?
(8000lines is not a multiple)
400
800
1600
3200
6400
12800
Are the common ones I’ve seen.


You are right 800 lines (8000 is a typo error, my mistake).
In my small world, lines 3200, 6400, 12800 are used for diagnostics not for typical data collection for a small machine.
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