Interpreting vibration spec

[elbrownos]

Hi All

I have an environmental specification for a PLC which I'm struggling to interpret.

Vibration
Functional Stress

5Hz to 9Hz​

Continuous

1.7mm amplitude​

Occasional

3.5mm amplitude​

Withstand

10Hz to 150Hz​

Acceleration

0.1g​

Endurance

10Hz to 150Hz​

Acceleration

0.5g​

What are the definitions of Functional Stress, Withstand and Endurance?
Any help appreciated.

Cheers
elbrownos

 

[btrueblood]

I'd contact the manufacturer, because otherwise you are guessing.

But if I were guessing (who can resist?),

"functional" levels are the vibration frequencies and amplitudes under which the unit is verified to remain functional, i.e. control of your process is continued un-interrupted. Likely, the 5-9 Hz range is where the relay outputs are resonant, and amplitudes somewhere above those listed may cause intermittent, unintentional, open/close of the relay contacts.

"withstand" - unit is rated to withstand these levels, though function is not guaranteed, without sustaining permanent damage. Most likely set by a combination of testing and stress/fatigue analysis.

"endurance" - likely a level of acceleration verified by testing over some fixed duration, below these levels no failures were observed.