Re: Replacement NAS?

On Tue, 24 Feb 2009 00:48:43 GMT, Johnny B Good
<jcs.computers***@xxxxxxxxxxxxxxxx> wrote:

The message <ov76q4pkoqbmd9a4r5i40skrpd43kn53ev@xxxxxxxxxxxxxxxxxxxxxxx>
from Jaimie Vandenbergh <jaimie@xxxxxxxxxxxxxxxxxxxxx> contains these words:

On Mon, 23 Feb 2009 20:55:14 GMT, Johnny B Good
<jcs.computers***@xxxxxxxxxxxxxxxx> wrote:

What caught my attention here, was the discussion of power consumption.
The figures quoted do appear to be within reason (each drive being
expected to account for approximately 8 watts in the 'power budget' as
measured at the mains socket), but, knowing the difficulty of obtaining
measurements of reasonable accuracy for relatively low powered non
linear loads, I'm intrigued enough to ask exactly how these figures were
obtained.

In my case, a Maplins 15quid digital power meter at the wall socket
set to average watts and run for a couple of days. So nothing special,
and known susceptible to dodgy readings at lower power, but it has
shown a change from an indicated 38W with 4x500gig drives to 31W with
3x1Tb drives which seems so sensible that I pretty much trust it.

Cheers - Jaimie

Thanks for that. I did take a look on the maplin website to see what
they had by way of 'Power and Energy Monitors' (the search term
'wattmeter' came up dry). I couldn't see any as cheap as your example,
but I was quite impressed by the specs on the Prodigit Electronics
2000MU-UK plug-in power monitor they were selling for 23 quid.

Mine isn't a branded item, and I'm certain I don't have the leaflet
that came with it any more. When I get home I'll check to see if
there's anything informative on the case at all

They had a cheaper 'Energy Monitor' at 20 quid with slightly inferior
specs (claiming wattage readings down to 0.2 watt and no mention of a
+/- 10 watt error - so a vast improvement over the cheap sub ten quid
meters;-)

It looks like it is now possible to get reasonable accuracy from sub 50
quid consumer grade 'Power and Energy Monitors' when monitoring the
consumption of low power (sub 50 watt) electronic gadgets.[1]

OTOH, it could just be a coincidence. Just trying to recall what other
sub-100W devices I've tried it on - a PC that came up at around 70W
(believably), and an unloaded APS 1400VA UPS that came up as using 20W
when not charging (I have no idea what the load characteristics are of
such a device).

All these are repeatable. I'm not sure if you're expecting consistency
from the ropier +/- 10W devices or not?

I've got to say your meter seems to be devoid of the +/-10 watt error
that seems to have plagued the earlier models being sold in Aldi,
Wallmart and similar outlets. The readings you got pretty well match up
with expectations, especially if the resolution is limited to units of 1
watt.

Which it does, kindly. Measures mains volts to 0.1, and matches my
analogue voltmeter; I've not compared amps because I've not got a
harness to test mains-plugged ampages - that's why I bought the
wattmeter!

BTW, if you fancy testing with "known" low power non-linear loads, the
electronically ballasted CFLs make a good substitute smpsu load and are
generally within 10% of their marked rating,

I'd have to yank some wires to do that; I've no pluggable CFL kit.
I'll give it a go next time I'm messing with the hardwired ones,
thanks for the suggestion.

[1] For the past couple years or so, I've often seen references to
'weird' power readings by the cheap (10 to 20 quid) meters that various
usenet posters have experienced in their use. It's nice to see that
better and more accurate models are finally becoming available at
affordable prices.

I still won't be surprised if it is merely a coincidence!

Cheers - Jaimie
--
I was most impressed when I looked up into the London sky and saw
a star through all the light pollution. A few of us checked some
astronomy references to try and identify it, and we're reasonably
confident that it was Sol. -- Peter Corlett, asr
.