Jacarta intelliAmp - Would L & N not cancel each other out?

[eveares]

So I saw this in a magazine at work today:

Jacarta Current Clamp

• eveares
• 25 Sep 2017

The PDF on it is here: http://www.jacarta.com/wp-content/uploads/2016/07/Jacarta-intelliAmp-2016.pdf

Apparently, it can measure power and current by simply clipping it over an active and already existing 3 core 16A/32A cables! (As in the ones that look like caravan electrical connectors.)

How does this work as I would have thought the magnetic fields of the Line and Neutral conductors in the cable would cancel each other out, hence why normally you put current clamps just over one current-carrying live cable!?

Regards: Elliott.

 

[JohnW2]

How does this work as I would have thought the magnetic fields of the Line and Neutral conductors in the cable would cancel each other out ...

Dunno - I would have thought the same as you, whether it uses inductive coupling or Hall Effect devices.

Hopefully someone will enlighten us!

Kind Regards, John

 

[aptsys]

A series of hall effect sensors can measure current in a device like this. I worked on a prototype many years ago but at the time it was cost prohibitive.

 

[JohnW2]

A series of hall effect sensors can measure current in a device like this. I worked on a prototype many years ago but at the time it was cost prohibitive.

Thank - interesting. How does even that work since, just like eveares, I would have thought that the L and N magnetic fields would simply cancel?

There presumably must be some 'problem' (still cost) since, otherwise, I would have thought that such things would be very common - since it would address the main drawback of 'clamp meters/sensors'.

Kind Regards, John

 

[ban-all-sheds]

How does this work

[email protected]

 

[Edddd]

A cable with parallel cores could be seen as an extremely elongated, single-turn solenoid. So from a position above or below the plane in which the cores lie you would detect a magnetic field.

Problem is, unlike in a normal clamp meter, you can't capture the flux for accurate measurement by enclosing it with an iron loop. Because as you say, the total flux through any loop around the entire cable is zero. So any measurement from a hall sensor would be highly dependent on its precise position relative to the cores.

Maybe with an array of hall sensors you can solve this with a function of all the measurements. Or maybe it requires calibration from a known load in every installation. Or maybe it makes assumptions about the physical dimensions of the cable.

 

[JohnW2]

.... So any measurement from a hall sensor would be highly dependent on its precise position relative to the cores. .... Maybe with an array of hall sensors you can solve this with a function of all the measurements. Or maybe it requires calibration from a known load in every installation. Or maybe it makes assumptions about the physical dimensions of the cable.

Thanks. One interesting point about the 'Specification' in the pdf posted by eveares is the absence of mention of anyhthing to do with accuracy.

Kind Regards, John

 

[winston1]

Even if it can measure current it cannot possibly measure power. To do so it needs to also measure voltage and phase angle neither of which it does.

 

[aptsys]

A cable with parallel cores could be seen as an extremely elongated, single-turn solenoid. So from a position above or below the plane in which the cores lie you would detect a magnetic field.

Problem is, unlike in a normal clamp meter, you can't capture the flux for accurate measurement by enclosing it with an iron loop. Because as you say, the total flux through any loop around the entire cable is zero. So any measurement from a hall sensor would be highly dependent on its precise position relative to the cores.

Maybe with an array of hall sensors you can solve this with a function of all the measurements. Or maybe it requires calibration from a known load in every installation. Or maybe it makes assumptions about the physical dimensions of the cable.

On the system I worked on, there was an array of hall effect sensors around the circumference of the clamp. You could then simultaneously sample all of the sensors and evaluate where the individual cores of the cable were and then use an algorithm to calculate the current flowing through the cable.

 

[Edddd]

Even if it can measure current it cannot possibly measure power. To do so it needs to also measure voltage and phase angle neither of which it does.

You could measure the phase of the voltage by capacitance. Place conductors on either 'side' of the cable and measure the electrostatically-induced voltage between them. Measuring the amplitude of the voltage would be more difficult because of the cable size/placement/arrangement uncertainties.

Or maybe there is a plug-in unit that measures voltage centrally for multiple clamp sensors: 'Multiple sensors can be monitored from a single monitoring device'

 

[JohnW2]

Even if it can measure current it cannot possibly measure power.

Very true, but it doesn't claim to measure anything other than 'true RMS current', so your comment is not really relevant to this product.

Kind Regards, John

 

[JohnW2]

You could measure the phase of the voltage by capacitance. Place conductors on either 'side' of the cable and measure the electrostatically-induced voltage between them. Measuring the amplitude of the voltage would be more difficult because of the cable size/placement/arrangement uncertainties.

AS I've just written to winston, it doesn't claim to measure anything other than current.

Kind Regards, John

 

[Edddd]

On the system I worked on, there was an array of hall effect sensors around the circumference of the clamp. You could then simultaneously sample all of the sensors and evaluate where the individual cores of the cable were and then use an algorithm to calculate the current flowing through the cable.

Sounds clever! Did it work, despite the cost?

 

[EFLImpudence]

I am puzzled why it states this:

and then this:

 

[ban-all-sheds]

A cable with parallel cores could be seen as an extremely elongated, single-turn solenoid. So from a position above or below the plane in which the cores lie you would detect a magnetic field.

But the cores do not lie in a plane.