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Topic Title: Electronic Energy Meter in a Microwave
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Created On: 20 September 2011 06:31 AM
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 20 September 2011 06:31 AM
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port500

Posts: 2
Joined: 22 December 2010

Hello,

I am in a bit of sticky situation and would welcome all ideas in this regard. My client has this problem where people are, literally, frying the energy meters in their homes using apparatus that is similar to a microwave.

So, i have been given the task to find out what fault does the microwave induce in the energy meter. What i am doing i pretty simple, placing a energy meter (with battery) in a microwave for 5 seconds. What i have observed is it takes about 2-3 seconds for the meter to go dead. A spark is observed and the display goes dead after that.

After examination of the dead meter, i found out that the resistors connected with shunt and CT are fried.

I have repeated the experiment by removing the battery and the resistors, mentioned above, but the spark is still observed after 2-3 seconds and meter goes dead.

I can't seem to figure out why is the meter acting out the way it is. Any ideas?
 20 September 2011 12:40 PM
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oneye

Posts: 161
Joined: 25 February 2008

This must be joke of the week - Yes .....

Who has home apparatus similar to a microwave - and why would they 'cook' an energy meter

Do tell !
 21 September 2011 05:53 AM
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port500

Posts: 2
Joined: 22 December 2010

It is quite serious actually. The reason why it is done is to escape the energy billing, as it usually takes 3-4 weeks to replace a faulty meter. An ingenious, yet still illegal, methodology.
 21 September 2011 06:36 AM
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gkenyon

Posts: 4478
Joined: 06 May 2002

Are you sure it's a microwave device, or just something that gives a HEMP?

If it's a microwave, I'd immediately think of three fault-causing mechanisms, but would assert that, potentially, each could lead to random parts failing:

1. Photo-electric effect damages electronic components directly. The device will contain at least one IC, porbably disaplay unit, and a number of ancillary components, that could well be damaged individually or simultaneously by this.

2. Localised heating damages one or more components.

3. High-energy electromagnetic pulse induces currents (and corresponding voltages).

The problem with any of these, is that I'm not sure there is a simple method to prove conclusively that it's a microwave device that did it? And I'd assume that it's possible (likely?) that more than one component will be seen to fail?

So does this mean the only way forward with these cases, is to gather empirical data on the parts damaged after exposing a suitable quantity of meters in a microwave oven, then analysing the products allegedly damaged by users to see if they exhibit a number of the failure modes characterised by microwave exposure?


Plan B - Try another approach to energy billing. Without knowing the individual circumstances, I'll throw in a couple of ideas:

1. Analogue Meter (assuming they're still available)?

2. Pre-payment type meter, so if the meter stops working, no power?

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH
 21 September 2011 06:40 AM
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gkenyon

Posts: 4478
Joined: 06 May 2002

Originally posted by: port500

It is quite serious actually. The reason why it is done is to escape the energy billing, as it usually takes 3-4 weeks to replace a faulty meter. An ingenious, yet still illegal, methodology.
And the assumed method has now been advertised on the internet via IET web-site and this page: http://www.thenakedscientists....41.msg367721;topicseen

Ingenious.

Hopefully people won't be foolish enough to try it out - results could be serious (fires, fatailites) in some cases - I'm sure we'll get some "natural selection applies" replies to this?

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH

Edited: 21 September 2011 at 06:51 AM by gkenyon
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