You're in luck! Much of what you want to do can be done for almost nothing.
Several years ago when I was interested in knowing more about the power coming to my PCs I had a Uninterruptable Power Supply made by APC (American Power Conversion). Most of their models, except for the very lowest price ones, came with the ability to tell you just about everything you could be interested in about the power line voltage through a DB-9 connector on the rear. These models went by the name 'Smart UPS'. The software, provided by APC, was called 'Power Chute'. Any company that made UPSes for servers had features like this and software to go with it. The status of the power line is important for a computer server and an IS manager to know. So, the UPS would report the line voltage at intervals you selected via its built in A/D, the magnitude and duration of all over voltage transients or drop outs, the line frequency, the status of the batteries, etc. In the event of an imminent loss of power the UPS could tell the server how long the batteries would last. Many of these messages had settable limits so you could specify a 'normal' range for each of these events. In addition, for each condition you could specify an action to be taken (email someone, dial a pager number, shut the server down, etc). Lots of interesting things can be found in the logs kept by the UPS software about the status of the power coming into a server. In addition the server could tell the UPS to test itself periodically to verify and recalibrate the charge on the batteries, etc. The batteries in a UPS wear out in 5 years (just like a car battery). Most people don't know that the bateries are easy to replace. You can buy replacements on-line or through a local alarm company. But because the batteries wear out people think the UPS went bad and usually they throw the UPS out or take the UPS to a local recycling station. You ought to be able to find one with the smart features in it for next to nothing. You don't need to have good batteries in it to be able to use the smart interface to start monitoring your power line voltages. Dennis -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Hal Murray Sent: Thursday, April 17, 2008 11:10 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Power monitoring My power went out the other day. That reminded me that I've always been slightly curious about that area. Are there any not-expensive boxes made for this? Or something that shows up on eBay occasionally? If I was doing it myself, I'd start with a low power (quiet) PC and a UPS. Then I'd have a platform that could monitor other things too, like temperature. Step 0 is just to measure when power is/isn't there. I assume the UPS has a signal for that. Step 1 is to measure the voltage. This takes an A/D. The standard PC audio input might be appropriate. I'd probably use an AC wall-wart transformer for isolation and a couple of resistors to get down to a reasonable voltage. Step 2 is to catch dips and spikes. That's just software behind the A/D. (assuming the A/D is fast enough) As long as I'm dreaming... Suppose I wanted to measure the power my whole house is drawing. What's available along the lines of a current transformer on the main lines? My first thought is that nobody does that (for homes) so it's probably horribly expensive. On the other hand there is a lot of interest in energy conservation these days so it might only be somewhat expensive. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.