In article ,
"G&M" writes:

"Grunff" wrote in message
...
Again, I've found this to vary greatly between makes. Some are very
poor, taking 10mins or more to reach max output, while others do so in a
few seconds.

The time is actually programmed in by the manufacturer. Most now use the
STMicroelectronics chip and it is easy to set this from 1 second to days.
The slower it turns on the longer the tube will last.

You are referring to the preheat time (normally around a second).

The issue is the run up time, which is the time to get the mercury
vapour up to operating pressure. This is minutes, as it requires
heating the amalgam pelet to release the right amount of mercury,
and having it diffuse throughout the tube. This will vary with
the length of the tube, where the pellet is retained (if it's
retained at all;-), ambient temperature, how long since last run,
etc. There are also a few different ways to govern the mercury
pressure which various different manufacturers use.

Unfortunately, for small tubes which run hot and at widely
varying temperatures depending on luminare, no one seems to have
come up with a way to get them to operating pressure quickly.
For the traditional linear tubes which run warm and at a more
predictable temperature, they were simply dosed with the right
amount of mercury to run at 40C (25C ambient) without the need
for some means to keep the mercury pressure right over a wide
temperature range. So although they also have an appreciable
run up time, the light output difference at the start and end of
the run up is not normally as noticable, and if you run them at
the wrong temperature, the light output drop often didn't notice
either. They could be manufactured for alternate operating
temperatures, such as inside industrial freezers, or sleeved
to keep them warm but then you do notice the run up time from
very cold.

--
Andrew Gabriel