Have I just bought some fake cable?

[JohnW2]

I am not sure what to do I suppose I best not risk it as it is to extend the washing machine flex so a quite a bit of current will flow through it. The problem is I only need 2 metres which limits where I can buy it from. B&Q and Screwfix both want well over £10 for 5 metres of Tower branded stuff.

The likes of TLC would cut you any length you wanted, but the postage would probably cancel any advantage. If it were me, and I didn't actually have any new cable lying around, I think I would be searching my cellar and garage for discarded appliances with suitable cables to 're-cycle'!

Screwfix, Wickes and and of the 'sheds' would sell you a '13A' 2m 'extension lead' for well under £10. If the cable looked OK, you could chop it off and use it (it would probably be 1.25 mm², but that should be OK for you) - and, if it wasn't a moulded one, you might even end up with a spare BS1363 plug as 'profit'!

Kind Regards, John

 

[NewOrder]

I do have a small oscilloscope multi meter which I use for measuring the output of DC power supplies (e.g ATX PC power supplies) I am not sure how good it will be at measuring low resistance. The retail price was about £250 but I paid £50 from a bespoke loud speaker manufacturer who had just upgraded theirs so it is a good quality meter.

 

[Monkeh]

I do have a small oscilloscope multi meter which I use for measuring the output of DC power supplies (e.g ATX PC power supplies) I am not sure how good it will be at measuring low resistance. The retail price was about £250 but I paid £50 from a bespoke loud speaker manufacturer who had just upgraded theirs so it is a good quality meter.

Well if you give us a make and model we might be able to tell what it's capable of.

But I suspect it's inadequate for the task.

 

[DetlefSchmitz]

Don't forget other ways of making the measurement. For example run an electric kettle through the test cable and measure the voltage drop. According to John's figures there should be slightly over a volt with a 13A load. You would need to do the sums yourself based on the kettle load.

 

[JohnW2]

Don't forget other ways of making the measurement. For example run an electric kettle through the test cable and measure the voltage drop. According to John's figures there should be slightly over a volt with a 13A load. You would need to do the sums yourself based on the kettle load.

Indeed, I almost suggested that.

Bear in mind, however, that the figures I mentioned assumed that all three conductors of the flex were connected in series - that obviously could be done in series with a load, but one would have to be careful about how the connections were all being made. However, I fear that the weakness in this approach would be knowing exactly what current was flowing. It would obviously be much safer to use a low voltage supply (e.g. car battery) and an appropriate load (e.g. headlamp bulb) - but, again, one would need to have accurate knowledge of the current flowing.

If one just used the 3-core flex as an 'extension' for the kettle (or whatever load) (i.e. with the 3 cores used separately), then the resistances, hence voltage drops, across each conductor would obviously only be one-third of the figures I mentioned.

Kind Regards, John

 

[NewOrder]

My metre is a UNI-T UT81B http://www.amazon.com/NEEWER®-Handheld-Digital-Multi-meter-Oscilloscope/dp/B00AE2J0SW

Is actually way over the top for what I need it for but it looks good on the bench and it gives more accurate measurements than a standard multimeter would.

 

[Spark123]

I doubt it will measure accurately enough to do milli-ohms.
The one I have is just for measuring milli-ohms and uses 4 wires to null out the lead resistance.
I think it is this one: http://www.rhopointinstruments.com/M210.html

 

[JohnW2]

My metre is a UNI-T UT81B http://www.amazon.com/NEEWER®-Handheld-Digital-Multi-meter-Oscilloscope/dp/B00AE2J0SW.[/QUOTE]
In that Amazon listing, "Ω" has obvioulsy come out as "W". Whatever, if you look at the manual, the lowest resistance range ("400Ω") has a resolution of 0.1Ω and an accuracy of ±(1.2%+5). That really isn't good enough - both 0.096Ω (1.5 mm² flex, 3 x 2m conductors in series) and 0.138Ω (1.0 mm² flex) would presumably probably be measured as "0.1Ω", even after you had corrected for the resistance of the test leads.

However, if, as Detlef suggested, you can find a way of putting an accurately-known (high) current through the flex, the voltage-measuring accuracy/resolution of your meter ought to be adequate for the purpose.

Kind Regards, John

 

[Monkeh]

My metre is a UNI-T UT81B http://www.amazon.com/NEEWER®-Handheld-Digital-Multi-meter-Oscilloscope/dp/B00AE2J0SW

Is actually way over the top for what I need it for but it looks good on the bench and it gives more accurate measurements than a standard multimeter would.

With 0.8% DC accuracy, no, it really doesn't give more accurate measurements than a normal multimeter. Handy device, but don't fool yourself into thinking it performs any one of its functions well.

 

[JohnW2]

I know that we live in financially hard times, but I'm not at all sure that all the time and effort that is being expended (by myself and others) in relation to this issue is necessarily prudent or appropriate, given that 5m of reputable (Tower) 1.5 mm² flex (in a choice of black or white) is available from B&Q for £8.58 - and, I imagine, similarly from other 'sheds'

Kind Regards, John

 

[NewOrder]

£16 from what I can see for that Tower cable. I am not going to bother testing the cable, I am just going to keep it in spare in case I need it for any low power applications and I will buy a new cable for the washing machine.

However I always like to learn new things so the testing ideas are not wasted .

 

[JohnW2]

£16 from what I can see for that Tower cable.

I'm not sure what you're looking at. If you click here , your £8.58 will get you 5m of heat-resistant 1.5 mm² flex

I am not going to bother testing the cable, I am just going to keep it in spare in case I need it for any low power applications and I will buy a new cable for the washing machine.

Given that you're obviously concerned, that's undoubtedly the best course.

However I always like to learn new things so the testing ideas are not wasted .

Oh, sure, it's been a fun discussion - but probably not actually 'appropriate' for solving your actual problem!

Kind Regards, John