Simple, Cost effective Power Meter Install ?

[clockmanFRA]

Sanity Check please…. Ha ha yes I know?

I am a really simple chap, with simple methods, and sometimes the intercricy of Electrical stuff can seem to me very bamboozling.

As Turbineers are aware, when the Tristar Controller is set in Diversion Mode, ie, it dumps excessive energy to matched heater dumps/loads when the batteries are full, so the Turbine is always kept under load.
But, the Tristar has No DATA store on what the Turbine is generating, as its just the Dump energy data that is retained.

Anyway for a few years I have been on the look out for a simple, cost effective, reasonable power meter with time base that can give me energy created and store the Data. Yes I read the topic regards the Twingy all singing and dancing thingys, but they seemed safe if they ran from a Shunt?.

Anyway, I have these 2 to try out and would appreciate your comments. http://www.ebay.co.uk/itm/350846579367?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
And    http://www.ebay.co.uk/itm/181289957019?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

My Turbines are Hugh Piggotts design 3.7m diameter, and the No 3 is being modified for a power meter. (I have seen, in a storm, very briefly, max power, 42a at 62v)

The Normally installed separate DC Amp meter has a shunt on the Positive side after the rectifiers.

The New Power Meter has a shunt on the Negative side after the rectifiers, but it seems odd,? Am I going to have issues with these Shunts?

Please Chaps and chap'ess do have a gander at the below Pics and please comment if you think this new power meter is a Howler/Smoker.

Pic1.
My Schematic for the Turbine Control box, (normal stuff from Hugh's book), showing  the New Power Meter.

Pic2.
Circuit etc for the Power Meter.

Pic3.
Box lid with Amp Meter and the Power meter to fit in.

Pic4.
No 3 Turbine Control Box with the new Power Meter Shunt and bit of PCB installed in its own box.
(please ignore the dangling cables as all is not  finished yet)

[OperaHouse]

I just started looking at those.  I was thinking about buying the 20A version and using my own shunt to take it up to 100A.  I have done that with the Turnigy units and just wondered if there was some jumper for amp range on the circuit board.

[Mary B]

Shunt can be in either the positive or negative line when measuring DC amps. Depends on the meter is all.

[SparWeb]

I've fiddled with this before.
Having the shunt on the positive side or negative side depends on the design of the data logging circuit to measure the voltage drop across the shunt.  I would prefer it if the shunt is on the positive line, myself.  Then the turbine's DC appears to be "62.1V" while the battery only sees "62.0V" and the Tristar will regulate accordingly.  Not a big deal, but some devices won't work that way.

Having the shunt on the negative side made me scratch my head for a long time too.  If I wasn't careful I would have been "raising" the battery ground above the earth ground or some similar kind of mistake.  I think the solution was to be aware that the turbine's "pseudo-ground" potential is not equal to "true" ground, and be diligent about using only the battery negative terminal for the "true ground" reference.

You're sure the little meter is well designed - the negative shunt isn't a "shortcut"?
With a little work, it is always possible to create a circuit to measure a voltage differential, and report the output to an isolated circuit that actually handles the display/recording.

[clockmanFRA]

Thanks SparWeb for your comments, I think you have hit the Proverbial 'Nail on The Head' regards pseudo-grounds.

My main concern was the meter wanting a positive reference ground. But where should I take the reference ground from, ie which side of the Ammeter Positive Shunt, battery or Turbine side.? ?

At the moment I have the new Meter Positive ground on the Turbine side of the Positive Ammeter shunt, as I am using the 3 wire system to power the New Meter from the battery 48v supply. The New Meter has a jumper pin and I have altered it accordingly, so their 1k 0.6w resistor on the supplied little PCB is now functioning with the Positive Ground before it disappears into the Meters Box of Tricks.

I have bench tested the meter and run the shunt and all seems okay. ...... Famous last words.

[SparWeb]

Strange coincidence.

I haven't thought about shunts in a while, then you ask your question, then the next day I get a news item from Texas Instruments with this:

http://www.ti.com/lit/an/slyt571/slyt571.pdf

So now you know that even the almighty TI will condone both high-side and low-side shunts.

[just-doug]

i have the second one you show,for over a year now.use with the supplyed shunt.did not come with the little circut board as your first pic.volts reads real good.amps must be calerbated,set,.with out a standard to set to ,amps are unreliable.it wont set amps to zero reliably even.no amps not possabile to get real energy,watts.additional,amp meter decimal location will limlt max amps to 9 before needing more room on the display.wast of money really