On Fri, 09 Jan 2009 11:01:18 -0200, you wrote:
I'm writing a program that will read medical signs from many patients. It's important to have a precise measure of the time interval between some signs, and that can't depend on adjustments of time. (Supose my software is running midnight at the end of a year with leap seconds. I would get wrong time intervals.)
If you really need that level of accuracy, there is nothing available on an off-the-shelf machine that will do the job. You need an independent timekeeping source of some kind, one that is not subject to the vagaries of reboots and other upsets. Perhaps the simplest and least expensive of these is a computer-compatible GPS time receiver. Since GPS works on GPS time (which has a constant offset from International Atomic Time), rather than UTC, you avoid having to deal with leap seconds and the like. I haven't tried doing it myself, but I know that most recent-vintage GPS units have a computer interface over which you can download the current GPS time from the device. There are many other kinds of GPS time receivers available, including ones that plug directly into a PC slot. Here's one that I found using a Google search on "GPS time receiver": http://www.franklinclock.com/gps_receivers.htm The prices range anywhere from a couple of hundred dollars for consumer-grade equipment to many thousands for high-reliability devices. The only drawback to this approach that I can think of is if the hospital is in an urban area with lots of tall buildings, it might be difficult to obtain a GPS signal of high enough quality. Some of the purpose-built GPS time receivers have better antennas than a consumer-grade GPS device. Steve Schafer Fenestra Technologies Corp http://www.fenestra.com/