Modular KWh meter with pulse (S0)

[Jfn]

Surfing the internet looking for a (cheap) modular KWh meter with S0 output I came across this meter:



It looks the same as the meters provided for example by Eltako. Including shipping it cost me 40 euro's. This included 2 seal-caps (to isolate the 220V lines from the rest of the fusebox)

And although it is not premier quality (the locking mechanism is made of plastic) it does its work very well. Counts 1000 imp/KWh (S0), has a bright led that flashes every time you consumed 0,001 KWh. I fitted it right after the fuse protecting the airconditioning. It displays two decimals, so 0,01KWh is the minimum it can display.

As soon as the extra 1-wire counter arrives I will hook it up to my 1-wire setup.

You can find the unit at this URL: http://www.eprotech.nl/shop/kWh-meters-p-1-c-16.html

They also sell a analog version that is even 3 euro's cheaper.

Als het niet gerepareerd kan worden dan is het niet kapot!

[Noel]

Looks very interesting!

--
Never start anything you can't fi

[Kroonen]

Hi,

is the S0 output that generate the pulses for 1-wire or do you need to get the flashes? Do you need it for every groep of for all three groeps?

[Jfn]

I connected the KWh meter to the fuse next to it.

So: Mains ---> Earth Leakage Circuit Braker (short: ELCB; In Dutch: 'Aardlek') ---> Fuse ---> KWh meter --> Load (In my case the airconditioning).

This way the KWh meter is always switched-off from the mains whenever there is a short-circuit or an earth-leakage.

You can connect the KWh meter between the ELCB and the fuse but I would not recommend that (In case of a short-circuit it is not protected). The ELCB then serves 3 fuses, so the KWh could be used to measure 3 groups. But as I said, I do not recommend this.

Besides the flashing LED (red colour, very bright!) it also has an S0 connection (two screw-terminals) hidden behind the fuse-cabinet. Connect 15V to the S0+ terminal and the S0- terminal goes to the 1-wire counter input.

You can count using the flashing LED, but as it has an S0 output I would use that. The S0 output follows industry standards. Connect it as described above and with a DS2423 counter you can start counting.

Als het niet gerepareerd kan worden dan is het niet kapot!

[MindBender]

That's a nice one! It would be excellent to have one on each circuit, though that would widen my fusebox considerably.

Can you tell anything about it's accuracy? Modern TV's nowadays use advanced power supplies that regulate using hit-and-miss algorithms, make power consumption measurement pretty hard.

[de.lesse]

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by MindBender</i>
<br />Can you tell anything about it's accuracy? Modern TV's nowadays use advanced power supplies that regulate using hit-and-miss algorithms, make power consumption measurement pretty hard.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">I'm sure if it can handle the Cos-Phi that you have a good one.

if you have inductive power connected like beamerlamps, tl-lamps, motors, plasma tv, ... Then you really need it.

<i>in nl; CosPhi is de hoek tussen de spanningsvector en de stroomvector. De cos phi wordt ook arbeidsfactor genoemd. </i>

i'm also searching a while for a good one.. but on ebay there are many kwh meters with s0 output, and if they are good... who knows..[8D]

[Jfn]

I will be using the meter to watch energy consumption of the airconditioning in my house and maybe the washing-machine (Will be ordering two of those KWh units more soon)

About accuracy when measuring imaginary loads, I do not know.

According to the specs it follows the IEC61036 standard (whatever that may be), has an 1000imp/KWh impulse constant and can count up to 99999.99 KWh on the display.

The S0 terminal is specified as 12-27V, max 27mA current.

I do not really care about accuracy. I just want to know how much the airconditioner is consuming. Whether or not the measurement is off by tenths of a KWh is of no importance.


Als het niet gerepareerd kan worden dan is het niet kapot!

[Bwired]

They have a 3 phase counter as well, but no specs for that device. It also seems that its not for mounting in a fusebox.
http://www.eprotech.nl/shop/kWh-meter-3 ... p-145.html

[Jfn]

Just give them a call should you need any info. That is what I did and they were very helpful (Let it be known: I am not in any way affiliated with them)

I will be ordering two more KWh meters at the end of this month.

Today I received the extra 1-wire counter from Hobby-Boards. I will connect the meter to the counter when I finished some other projects (measuring gas usage, redoing part of the plumbing).

Occasionally I use the air-conditioner for heating, but a more intensive use (cooling) is still some months away, so no need to hurry.

Als het niet gerepareerd kan worden dan is het niet kapot!

[Jfn]

At the moment I have 2 of the KWh meters running.

I hooked both of them up to the same Hobby-Boards counter. According to the specs:

<i>Impulse connection: Voltage 12-27V, current <= 27mA, max length of lead: 20m. Impulse width=90ms. Limits of valuesL 60VDC, max 50mA</i>

However, my Hobby-Boards counter goes bananas when counting pulses. The flashing LED on the meter works perfectly, but applying +15V to the S0+ terminal and connecting the S0- terminal to the counter-input of the counter gives the following effect:

<i><ul>
<li>Counter A: Start: 2019378; End: 2019390</li>
<li>Counter B: Start: 59769244; End; 135071421</li>
</ul></i>

The circuit-breakers protecting both loads are switched on. Load A is not active, load B is switched on. The interval in which I took these measurements is about 20 seconds, meaning load B would have consumed (135071421-59769244) * 2 = 150MWh of energy. I know my airconditioner uses energy, but not that much

Anyone have a clue? I can imagine that the meter does not give out perfect pulses, but I cannot believe that it is that inaccurate.

I tried switching counters, but that did not help either.


Als het niet gerepareerd kan worden dan is het niet kapot!

[Jfn]

Found the clue myself! It was hidden in a box and was disguised as a 220 Ohm resistor.

I just realized that the strange behaviour I was experiencing could only by caused by an issue with the power-supply.

So what is happening? It seems the manufacturer forgot to put a resistor in series between the S0+ terminal and the power that is applied to it.

So: +15V --> Resistor 220R --> S0+

A picture says more than a thousand words:



Why 220R? Well, this makes sure that the maximum current stays below 27mA at all times.

Without the resistor, every pulse meant actually a short-circuit between + and -, explaining the strange behaviour.


Als het niet gerepareerd kan worden dan is het niet kapot!