so today I thought I'd take a closer look at this power meter thing that I
got in a recent mailbag maybe take a peek inside and see what makes it tick
I'll test it against a couple of other things and just see how accurate it is
so on the back of it here it says it's capable of reading voltage from 110 230
which is reasonable for North America up to 15 amps current up to 1,800 watts and
then calculating kilowatt hours and costs and stuff I'm not that concerned
about that stuff it claims to be cat 2 insulated which I guess is
reasonable enough don't recycle it see Ian Nortec symbol on it whether or not
those are legitimate who knows you can never be too sure when you're buying
this stuff from China actually I think I'll take a peek inside first and then
we'll test it out afterwards that sounds fair so there's three Phillips screws
holding it together
they're in there fairly tight too but we got them and it should just separate all
in that seam maybe with a little bit of gentle persuasion from one or another
spudger I think I'm gonna do this wait so the buttons don't fall out nope
okay so now let's look at this back here first we've got the AC input on this
little module here which can it pop out yeah it can so I guess yeah when I
bought this from eBay there were various different versions of
it EU North America Australia
that's UK etc so I'm guessing that little insert and this will insert here
just pop out so they're gonna drop a different one in so on the board there's
the current shot is it crystal huh and there is a little battery here nickel
metal hydride so it's rechargeable three point 6 volts 20 milliamp hour 14 hours
at 2 milliamps okay suppose we could see what its current state of charges
3.76 volts that's pretty much full that's good okay what else is on there I
assume that there's probably some stuff on the backside of that board take a
look at that oh yeah there's many many things back there okay there that makes
it easier now down on here I'm guessing this is just buttons and the display
over probably some kind of a serial bus and the interesting stuff is happening
here and yeah there is a VCC TX and rx going out to this thing okay there is
the obvious brains of the operation there is the current shunt so and then
some little passives on both sides there's a capacitor across it some other
capacitors and resistors they're going into the measuring chip and basically
just some some very basic components over here a couple of transistors some
of those little milf diodes that everybody hates because they bounce all
over the place and fall on the floor
yeah so I guess the only thing really to look into is that guy there which says V
9 to 6 1 F well that wasn't all that hard to find
vengo 5 volt power supply wide range 3 to 5 point 5 volts which is what the
battery is doing internal reference so there's a reference a 1 point 1 8 8 volt
reference inside it that it measures things across its crystal frequency
between 6.5 okay so it can take a couple of different fairly common crystals to
to run it that's handy it can handle a current transformer and shunt resistor
hmm we're all using a shunt resistor on this one okay
okay voltage RMS metering error typically 1% current metering typically
1% okay so we will keep that in mind point oh one Hertz error on the
frequency that's reasonable and again it can handle any of the world's power lien
frequencies between 40 and 70 Hertz oh it couldn't see will a measure
temperature I haven't seen that in the menus maybe they're not implementing it
in this one there's what's going on on this TX and rx it will be using to talk
to the the buttons and display there's it's reference voltage negative positive
inputs for voltages so it looks like it's rectifying the voltage to talk to
it probably if it's calling them negative
and positive all right we go there is the block diagram current input and the
voltage inputs goes to the EDC and into the math compares it against the
internal reference or you could guess apply an external reference probably
there's a temperature sensor inside yeah pretty much what you would expect from a
device like this I guess I'll just put this guy back together and then we will
see if we can play with it a little bit I get everything in alignment there
normally you wouldn't want to do that obviously
okay it's all back together now we can do a few tests on it I'm gonna use my
289 and when I say mine I mean borrowed from work as my reference and we'll just
compare against this guy and I've got a kind of a janky little thing set up here
to plug it into if you don't know what you're doing with this stuff don't do it
that's as close to a disclaimer as I'm gonna get
so the first test that we'll do is just to see how accurate the AC with the
voltage is and then twenty two point zero one hundred twenty two point six
nine seven that's close enough for me within what is that within half of a
volt that's pretty reasonable sixty Hertz it's saying sixty point zero zero
five oh yeah that's close enough for that alright
what's next current I guess that's the mean reason that I got this in the first
place
okay I've changed up the setting a little bit I've got the the fluke in
series now with the feed to this meter and I've got my good old I don't even
know how old this thing is my good old amp probe that I used to use back in my
life sound days I I don't happen to have my my foot clamp meter handy so I'm just
gonna use this guy instead it's not gonna be all that precise and it's
mostly just in here for fun I said that amps and coincidentally power factor yes
we need a load how about a 60 watt incandescent lightbulb
so we're showing half an amp there 0.50 six or one point five one four six here
that's pretty damn close next one's going to be this 12 watt dollar-store
LED light so what do we have here 97 milliamps there and 110 million there
that's a little bit further open not bad let's try it at a higher load though
okay the higher current tests that I've got
is my electric space heater which has two settings 750 ish and 1500 watts so
let's go there's 750 watt setting now as it heats up as the heating elements heat
up you should see the current rise and you can a little bit down here we're
approximately 4 amps and realistically for what this thing is designed to do
that's precise enough four-and-a-half amps at 4.2 4.3 again that's easily
within 1% or probably less actually just gonna wait for it to stay boys and then
I'll do a quick math again it's within 1% let's try it on
1,500 watts so here we are creeping up eight and a half nine amps I got to be a
little bit careful because this guy's fused at 10 amps but Ian's 9 point yeah
a couple hundred milliamps different fir what I'm doing that's close enough and
I'm gonna drop that down before I pop the fuse on this thing but yeah this is
all easily within 1% and I'm pretty pleased about that and when electric
heater even though the motor is inductive most of the load is is
resistive so of course it's showing a one point two zero zero power factor so
ya know that it's kind of stabilized look at that's close enough for anything
I'm gonna want to do it should I trust the wattage measurement or should I
actually do the math on it
so there's the wattage calculation and again that's easily within 1% which is
all close enough so I'm actually pretty happy with this guy starting to get a
little warm down here yeah that's uh that's very pleasing and this this old
boy is still close enough for the sort of usage that it's put to and actually
the amperages we were dealing with our way at the low end of what it's designed
for it's it's the sort of a thing that an electrician would carry and it can
handle up to a thousand amps so down in the single digits it's probably not all
that precise but it's perfectly fine for what it's what it's designed for and I
just like the look of this nice old boy don't you anyway um where was it yeah
back to this guy so I'm pretty please unplug this I'm pretty pleased at how
how close this thing is to a much more expensive piece of test equipment and I
know that I can trust it to be within 1% of reality which is most of what the
whole point of this this video was I hope you found that interesting I found
it informative of course if you got any comments or questions down in the
description below I'll put a link to the mailbag where I opened this up somewhere
and yeah I will talk to you later
oh yeah somebody's gonna ask this is turqu burling's roundabout English dark
mild ale