On Jun 8, 2004, at 4:06 PM, Bill Moran wrote:
Charles Swiger <[EMAIL PROTECTED]> wrote:

No need to guess, use an amp-meter. :-)

What a crazy idea.

I seem to remember plugging monitors into a UPS in an attempt to use the cheesy
"load meter" lights to tell which was drawing more juice, when that didn't
show us any difference, we tried watching the power meter outside ... trying to
guess which monitor made it spin faster ...

:-) The "smart" versions of UPSes (as in, APC's SmartUPS line) will often have a serial connection which not only does the "deassert DTR when the battery is low" thingy, but will communicate other information about the state of the UPS. That will include the power consumption of the load measured more accurately than 5 green LEDs would be able to show you.

A really serious UPS, such as a PowerWare 9330, may have ethernet and SNMP support and will do things like tell you the power factor of the load, typically about 0.9 for computer stuff. But I admit, a 20kVA UPS is outside of what a normal home user would want. And the batteries are freaking heavy... :-)

I have one machine with an AMD 1800+ (1.54 MHz T'bred-B), which runs at
perhaps 48 or 50 C if the system is idle. If I run something like
[EMAIL PROTECTED] for a day or so, the CPU will go up to around 56 or even 57 C
as a result of the load. The difference in thermal output due to load
is very obvious.

But is thermal output a reliable indicator of power usage? Logically, it seems
like it would be, but I'd hate to assume.

Conservation of energy is a law, so any assumptions being made are pretty safe.

When you pump 0.5 amps @ 120VAC into a 60 watt light-bulb, you end up getting about 54 watts of radiant heat and about 6 watts of visible light. A computer's CPU eats about the same amount of power, and sends a watt or so back out in terms of data signals, but most of the energy used by the processor to actually process data gets emitted as heat.


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