Do Residual Current Meters suitable for DIYers exist?

[JohnW2]

I did consider that but my (extremely) cheap and nasty multimeter doesn't do AC current.

I may be wrong, but I think you would have to go quite a long way 'up market' until you found one that did. I've had many multimeters over the years/decades (and currently have a good few, but I have personally never had one that can measure AC mA (and I'm not even certain about AC current at all).

In any event, as I have said, a multimeter wiuld not be useful in the case of a boiler, anyway, since it could only measure current in the CPC (earth) of its connection, and that is no good when leaks to earth may be going, at least partially, through other paths.

Kind Regards, John

 

[winston1]

I may be wrong, but I think you would have to go quite a long way 'up market' until you found one that did. I've had many multimeters over the years/decades (and currently have a good few, but I have personally never had one that can measure AC mA (and I'm not even certain about AC current at all).


Kind Regards, John

Really?

I have at least 3 multimeters that can measure AC current, one analogue bought many years ago at great expense, 2 digital, one from Homebase for around £35, and another with true RMS bought in the USA from Radio Shack.

 

[bernardgreen]

Winston!. Can your meters provide accurate measurements of AC currents in the range 1mA to 1Amp ?

If so please name them

 

[Harry Bloomfield]

I may be wrong, but I think you would have to go quite a long way 'up market' until you found one that did. I've had many multimeters over the years/decades (and currently have a good few, but I have personally never had one that can measure AC mA (and I'm not even certain about AC current at all).

In any event, as I have said, a multimeter wiuld not be useful in the case of a boiler, anyway, since it could only measure current in the CPC (earth) of its connection, and that is no good when leaks to earth may be going, at least partially, through other paths.

You are very wrong. Electricians instruments do often have a limited or none existent AC current range, but the more general purpose ones do include such ranges. I, without bothering to count, I must have around a dozen such instruments here, even three AVO 7 & 8's - all but two include AC mA ranges. Here is a cheap example https://www.ebay.co.uk/itm/Auto-Ran...543627?hash=item28853521cb:g:5dUAAOSwOCdfg9ki

• DC Voltage Range: 2V/20V/200V/600V

• DC Voltage Resolution: 0.001V/0.01V/0.1V/1V

• AC Voltage Range: 2V/20V/200V/600V

• AC Voltage Resolution: 0.001V/0.01V/0.1V/1V

• DC Current Range: 200.0μA/2000μA/20.00mA/200.0mA/2A/10A

• DC Current Resolution: 0.1μA/1μA/0.01mA/0.1mA/0.001A/0.01A

• AC Current Range: 200.0μA/2000μA/20.00mA/200.0mA/2A/10A

• AC Current Resolution: 0.1μA/1μA/0.01mA/0.1mA/0.001A/0.01A

• Frequency Range: 9.999Hz/99.99Hz/999.9Hz/9.999KHz/99.99KHz/999.9KHz/9.999MHz

I think we have already established that measuring the AC current in the earth conductor, in items which might have another path to ground (such as a boiler), might be futile. The only sensible way to check a boiler for leakage to ground, is by either comparing the current between L & N, or an insulation test.

 

[Harry Bloomfield]

I, without bothering to count, I must have around a dozen such instruments here, even three AVO 7 & 8's - all but two include AC mA ranges.

Having now done a count - I have 21 such multimeters meter, including seven Fluke. Three of the Flukes and one credit card novelty meter lack an AC mA range.

 

[Harry Bloomfield]

Winston!. Can your meters provide accurate measurements of AC currents in the range 1mA to 1Amp ?

If so please name them

My Fluke state 0.09% Basic Accuracy.

 

[bernardgreen]

AC Voltage Resolution: 0.001V/0.01V/0.1V/1V

Resolution is not accuracy.

 

[Harry Bloomfield]

Resolution is not accuracy.

As I am well aware. Digging a bit deeper into the manual, Fluke state 1.5% +/- 2 accuracy on the AC mA range.

 

[winston1]

Winston!. Can your meters provide accurate measurements of AC currents in the range 1mA to 1Amp ?

If so please name them

Depends what you mean by accurate. My Rapitest from Homebase has an AC current ranges of 200µA, 2mA, 20mA, 200mA, 2A, and 10A. I assume they are accurate enough.

 

[JohnW2]

My Rapitest from Homebase has an AC current ranges of 200µA, 2mA, 20mA, 200mA, 2A, and 10A. I assume they are accurate enough.

What brings you to make that assumption? ..., anyway, "accurate enough" for what?

 

[winston1]

What brings you to make that assumption? ..., anyway, "accurate enough" for what?

Since this discussion was about RCD trips accurate enough to measure current imbalance around 15 to 20mA.

 

[Harry Bloomfield]

I would expect even the cheapest meters to be far more accurate than the RCD's, which is all that really matters.

 

[JohnW2]

I would expect even the cheapest meters to be far more accurate than the RCD's, which is all that really matters.

That's probably true, at least for clean sinusoidal currents.

However, given that at least a couple of people around here can get fairly excited about currents which are not necessarily 'clean and sinusoidal' (e.g. those which have DC components and/or are pulsatile), in relation to 'types' of RCD, I wonder how these meters (any meters) perform in the face of such currents?

Kind Regards, John

 

[winston1]

I wonder how these meters (any meters) perform in the face of such currents?

Kind Regards, John

As I said one of my meters claims to be true RMS. (Which is why I bought it while on holiday). How sad is that?!!

 

[Harry Bloomfield]

However, given that at least a couple of people around here can get fairly excited about currents which are not necessarily 'clean and sinusoidal' (e.g. those which have DC components and/or are pulsatile), in relation to 'types' of RCD, I wonder how these meters (any meters) perform in the face of such currents?

No meter would be able to exactly match an RCD's response.