I found a cheap one of these also at Radio Shack-$79US that has the rs-232. using it and the laptop I can pretty much record continuously. I know we have used it for >12 hours. It came with radio shack software- I'll see if I can get u the exact info for software if you want. I'm always surprised that these quick impulsive purchases seem to become quite useful,this meter reads frequency as well so it has traveled along on jobs quite a bit, rather than the expen$ive fluke types.