'once per' vs 'once every'

[Thomas_Belgium]

Hello,
I'm trying to write a manual about a device that has a LED to indicate system activity. I had a discussion with a colleague regarding 'once per' vs 'once every'. To me, both seem correct without any preference.
Examples:
* The LED will blink at a rate of once per second
* The LED starts blinking at a rate of once every three seconds
* Blinking once per second: starting up
* Blinking once per three seconds: start up completed
Is there a right and wrong? Is there a preferred way of putting it? Please advise.
Thanks in advance!
Thomas (Belgium)

[BobK]

Hello,
I'm trying to write a manual about a device that has a LED to indicate system activity. I had a discussion with a colleague regarding 'once per' vs 'once every'. To me, both seem correct without any preference.
Examples:
* The LED will blink at a rate of once per second
* The LED starts blinking at a rate of once every three seconds
* Blinking once per second: starting up
* Blinking once per three seconds: start up completed
Is there a right and wrong? Is there a preferred way of putting it? Please advise.
Thanks in advance!
Thomas (Belgium)

All of your examples seem fine to me. Speaking personally, I'd prefer to use 'every' as you have done in your second example - i.e. before a number. But I've heard both.

b

[Thomas_BE]

Hi Bob,

'Thanks in advance' now becomes 'thanks afterwards'
Anyway, thanks!

Thomas