Time machine not recognised after unplugging

I'm not really a switcher any more since I am very comfortable with the mac now, except for this one thing. If I unplug the time machine external HD (which I like to do for security if we're away for a few days) when I plug it back in, the Imac doesn't recognise it as a backup and I have to start a new backup process.

Is there a way round this?

I have a 27" iMac with 8GB and 2TB, and a Buffalo external HD, which is only 500 mb but big enough at the moment.

Any ideas will be appreciated!

I routinely dismount my external Time Machine drive as I do not like automatic backups, however, whenever I mount it, it's recognized as such. I do the same on both of my machines with no problems with two different TM drives.

Try erasing the drive, reformat as Mac OS Extended Journaled, rename it and set it up again as your TM drive within TM preferences. Let's see if that works out OK.

Thank you - I'll certainly give that a try!

Are you ejecting the external drive or shutting down the computer before you unplug it. If not, that could be a cause of the problem.

Yes, I was ejecting before switching off and waiting for the iMac to shot down before unplugging.... I've been away for a couple of days and haven't reconnected it yet but will do so tomorrow. It'll be interesting to see if it's recognised this time.

Hmph... the external HD was recognised this time, even though I did nothing different, but now the machine won't power down. I disconnected the external drive and tried again but still had to do a forced shutdown via the power button...