Power Management Panel - Induction Type

[BlueSkyNick]

The following is an extract from the Sterling Power <A target="_blank" HREF=http://www.sterling-power.com/html/products-panel.htm>website here</A>, describing one of their battery management systems.

This model may look the same as the shunt type but that is where the similarity ends. Some people find shunts difficult to install as you must cut the cables in order to do this, and the thought of a live shunt makes people uncomfortable. The induction model measures the current using induction rings, where the cable is simply passed through the ring and the magnetic field around the cable measured and converted to amps. This is a much safer and easier installation and also offers 4 amp, 4 volt, and 4 Amp hr readings.

I realise its nearly 30 years since I did my HND, but I am sure DC still does not create a magenetic field unless the current is changing quite quickly.

So how does this panel work then? Has anybody installed one, who can say if its a worthwhile option.


<hr width=100% size=1>Never be afraid to try something new.
Amateurs built the ark, professionals built the Titanic

 

[Trevethan]

DC creates a strong mangetic force -- wind some insulated wire around a nail, attach to a 9volt battery and move a compass close by ---

Least ways when I did that in school about 25 years ago it seeme to work

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[Stemar]

Likewise rusty memories, but I as I recall, DC creates a constant field around itself. That's how a DC electromagnet works - and a battery ding-dong type doorbell. A heavy DC current in a wire can easily deflect a compass needle if too close.

You need AC in a transformer as it's the change in the field that induces current in the secondary coil

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[ex-Gladys]

It's the other way round, you need a changing magnetic field to produce current....

<hr width=100% size=1>Larry Botheras

Anderson 26 "Amber"

 

[steve_cronin]

See Me BOY!!!!!

I'm afraid that you're recollection of 3rd year physics Is actually letting you down. ANY current flow will generate a magnetic field. Around a single wire a circular field is generated.

The "Left Hand Rule" whereby you place your loosely clenched left fist thumb up on a surface. The thumb indicates the direction of electron flow in a wire and the curling fingers show the direction of the magnetic field. (See http://www4.ncsu.edu/~rwchabay/emimovies/left-han.html for a video)

If you arrange a series of continuous coils of wire ( a helix) then the magnetic fields combine and you end up with a bipolar array (an electromagnet or solenoid)

Clever, innit?

What you might be confusing is the principle of the transformer whereby a CHANGING voltage - either by breakdown as in a car ignition coil primary of by alternation as in an AC transformer, induces a corresponding current flow in an adjacent conductor. Arrange these conductors to be concentric helices around an iron core and you have either a step up or a step down transformer. (The ignition coil is just a specialised step up transformer)

Take 100 lines

"I must remember that all electrical current flow will generate a magnetic field and i must perform the left hand rule each morning before breakfast"

Steve Cronin

<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[steve_cronin]

Whilst doing the 100 lines....

Take a look at most high power electrical installations. They use inductive measuring equipment because it just isn't possible to intervene in the heavy duty wiring, Shunts are Ok but effectively you are trying to send a little of the current through a delicate meter - probably around 25mA for the needle to swing all the way over (FSD) but have the rest of it travel along the shunt.

Charles Sterling is absolutely right in that if you don't have to interfere with the wiring it is a better option and this may be of major importance if you don't want a warranty administrator to invalidate a claim.

I have no connection with this very talented Irishman but I have owned several of his products over the years, including his latest smart alternator controller and monitor which i am going to fit this weekend and apart from some rather fiddly fitting arrangements of his earlier battery chargers (which he tells me was due to a US market requirement) I can tell you that I am very impressed with the inovation, design and support given by his company & himself.

Give him a ring and you'll be impressed by the breadth of knowledge of the man but be prepared for a long phone bill, like most originating from the Emerald Isle, he can talk the hind legs off a dunkey!

Steve Cronin

<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[ParaHandy]

this certainly wouldn't work in a (very clean arse) Benny not far from you? too many stray magnetic fields ... which leads me on to ....

as for Magister Cronin ... well ... i seriously doubt that an accurate and consistent current value could be determined from the DC magnetic flux generated for the same reasons as you do ...

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[JEG]

I use a clamp meter to measure both ac & dc current - but I do not know the principal of operation: perhaps a manufacturer's site might elucidate - Fluke?

John G

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[BlueSkyNick]

Re: Whilst doing the 100 lines....

How are you going to fit your new alternator toy - I thought your boat is in Greece??

<hr width=100% size=1>Never be afraid to try something new.
Amateurs built the ark, professionals built the Titanic

 

[steve_cronin]

Re: Whilst doing the 100 lines....

Misser BIGNICK

I haf friend, he called Stelios.

Stelios haf big birds, fly from near car factory on M1

I haf tol Stelios that I use hiss elevenoclockfriday big bird this week.

OK?

Stefanos Chritarides

<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[BlueSkyNick]

Re: Whilst doing the 100 lines....

That's nice for you, have a good trip - rotten sod !

<hr width=100% size=1>Never be afraid to try something new.
Amateurs built the ark, professionals built the Titanic

 

[steve_cronin]

What is it? a de-gaussing vessel?

The pick up coils need the test wire to pass through them. Anything that a yacht's electronics can gneerate, even half an inch away (inverse square law) will have negligible effect and anything a few inches away virtually nil.

This method of measurement is widely used. Even BT technicians turn up with inductive test equipment these days.

Steve Cronin

<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[ParaHandy]

well put it this way ... if all reports of unexploded solent mines are half true, i'd think twice before going aboard!

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[steve_cronin]

Re: Whilst doing the 100 lines....

I'm already doing some shopping for one regular on here and some reccying for another so with six black boxes (no seven) to fit I will have little time to enjoy the scenery!

Steve Cronin

<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[ccscott49]

Re: See Me BOY!!!!!

Not sure, but I think you have the left hand grasp rule wrong, the fingers coiled, are in the direction of the current travelling in the coil and the thumb indicates the north pole of the magnetic field produced, or is that the rh grasp rule?? I can still remember the other three finger hand rule!

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[pvb]

Can\'t imagine it\'s very accurate...

Really can't see how this can be a very accurate way of determining Ah readings. Shunts are very simple things, and it seems absiurd to claim that "the thought of a live shunt makes people uncomfortable". But then, many of Mr Sterling's claims seem a bit extreme, don't you think?

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[Heckler]

Re: Can\'t imagine it\'s very accurate...

look at the previous post reference mr fluke, all pro electricians carry some sort of clamp meter for measuring amps, flukes are one of them, they work on induction and are pretty accurate, am not clever enough to know how or why they work but am clever enough to realise that they do. mr sterling is clever enough to know why and how and also clever enough to make money from his knowledge, trust him, i do
stu


<hr width=100% size=1>http://www.beneteau-owners-association.org.uk

 

[stuartw]

Easy peasy-All is revealed.

Most clamp-on measuremnts these days, rely on a semiconductor device which utilises the Hall effect.

Hall effect devices alter their voltage/current charectristics in the presence of a magnetic field. So your Fluke multimeter or Sterling sensor, is actually measuring a small current in the device, which is proportional to the magnetic field, which is in turn proportional to the current flowing in the conductor.

Hall effect effect devices are used all over the place, and in particular, in commutatorless DC motors, where the Hall effect devices actually initiate the switching of windings to create the rotation. Your PC will have a few of them.

So the Hall effect devices can be used as a switch or as a linear device to measure current or magnetic field strength.

Incidentally, they can be quite accurate, once calibrated.

Hope this helps

Stuart

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[ccscott49]

Re: Easy peasy-All is revealed.

I have one of these units and it is very accurate!


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[Como]

As others have said DC will create a magnetic field around any conductor. To measure this field all that is needed is a Hall Effect device within a magnetic circuit. These are produced by a number of companies (Honeywell for one) and can measure quite small fields some are sensitive enough to measure the Earths magnetic field.

The type used for this application are encapsulated with a hole for the cable and produce an output voltage proportional to the current flowing in the cable. If you are interested have a look on the RS web site (http://rswww.com).

Hope this helps.

ATB

John

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