new meter has no off-switch

[Wontdothatagain]

Do we know that none of the meters with output isolators/switches aren't DP?

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• Wontdothatagain
• 8 Jul 2011
• 2

I think i have a siemens meter somewhere, i will pull it apart later and check but it is allmost certainly SP

 

[JohnW2]

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• Wontdothatagain
• 8 Jul 2011
• 2

I think i have a siemens meter somewhere, i will pull it apart later and check but it is allmost certainly SP

Thanks. It occurs to me, BTW, that the meters with isolators I've seen are not Smart Meters, which may have confused the discussion a bit.

How is that meter doing 'metering'? Most of the load current is obviously going along that copper bar (the 'switch') - is it just monitoring the voltage drop across a short length of that bar, via the red/black pair (and monitoring the voltage between the blue and brown), or what?

Kind Regards, John

 

[EFLImpudence]

This is rather obvious but to reply to the correct post -

Work on or near live conductors
14. No person shall be engaged in any work activity on or so near any live conductor (other than one suitably covered with insulating material so as to prevent danger) that danger may arise unless–

(a)it is unreasonable in all the circumstances for it to be dead;

As for the neutral, it is impossible for it to be dead.

and .
(b)it is reasonable in all the circumstances for him to be at work on or near it while it is live;

Apparently that covers undoing two screws on the supply end (of neutral) however the live has been disconnected..

and .
(c)suitable precautions (including where necessary the provision of suitable protective equipment) are taken to prevent injury. .

That's reasonable.


So, all is well.

 

[Wontdothatagain]

Thanks. It occurs to me, BTW, that the meters with isolators I've seen are not Smart Meters, which may have confused the discussion a bit.

I have never seen a Smart Meter with an external isolation switch but several Smart Meter manufactures have a inbuilt isolation swith that allows them to phone into the meter and disconnect the supply.

This function is not designed for safe isolation. It was built in on the request of suppliers so that they can disconnect a customer without having to force entry into a property. At the present time they are not allowed to use the function in this way.

 

[Wontdothatagain]

How is that meter doing 'metering'? Most of the load current is obviously going along that copper bar (the 'switch') - is it just monitoring the voltage drop across a short length of that bar, via the red/black pair (and monitoring the voltage between the blue and brown), or what?

I am not sure of the actual working of the unit but i will take another picture of the reverse of the parts so you may be able to see something there.

 

[ban-all-sheds]

As for the neutral, it is impossible for it to be dead.

Not for you it isn't. For you it is possible for it to be dead.

Apparently that covers undoing two screws on the supply end (of neutral) however the live has been disconnected..

It covers it for a DNO or metering company employee who is authorised to do it.

Not you.

 

[JohnW2]

I am not sure of the actual working of the unit but i will take another picture of the reverse of the parts so you may be able to see something there.

Thanks. A close-up of where that red/black pair meet the copper bar/strip might be interesting. If it is measuring current by voltage drop along that short segment of the bar, considerable precision in the attachment of those leads would be required to get reasonable accuracy!

Kind Regards, John.

 

[JohnD]

I thought there would be a pick-up coil, or some kind of solid-state sensor.

 

[DetlefSchmitz]

If it is measuring current by voltage drop along that short segment of the bar, considerable precision in the attachment of those leads would be required to get reasonable accuracy!
Kind Regards, John.

Or a non-volatile case-by-case calibration setting in the processor.

 

[westie101]

On meters with an inbuilt switch, access is available to both the Line and Neutral outgoing terminals.

 

[JohnW2]

I thought there would be a pick-up coil, or some kind of solid-state sensor.

Same here. I was actually expecting to see a current transformer (plus voltage/phase measurement).

Kind Regards, John.

 

[JohnW2]

If it is measuring current by voltage drop along that short segment of the bar, considerable precision in the attachment of those leads would be required to get reasonable accuracy!

Or a non-volatile case-by-case calibration setting in the processor.

Yes, I suppose that would work. It would presumably needs some temperature compensating measures, too.

Kind Regards, John.

 

[JohnW2]

On meters with an inbuilt switch, access is available to both the Line and Neutral outgoing terminals.

Even if it is a SP switch?

Kind Regards, John.

 

[Wontdothatagain]

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• Wontdothatagain
• 20 Jan 2012
• 1

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• Wontdothatagain
• 20 Jan 2012
• 1

 

[JohnW2]

<piccies>

Right. Thanks again. Do I take it that the thing to which the red/black are connected looks like just a bit of copper or brass, with nothing else 'clever' going on? If so, then I guess that DetlefSchmitz must be right.

Kind Regards, John.