What is the cooldown on Watcher's "Flask charge on crit with precision"?

I dropped a pretty nice watcher's. And it got me thinking. The hatred itself is not that useful for me (miner), but with pyroclast I get A sh*tLOAD of crit hits. So getting a watchers with just the precision effect might be worth it for me.

But those effects live or die by the internal cd. So what is it? 1 charge every second? or 1 charge every 0.1 of a second?