Hi all,

I'd like to build my own PATS tester (Portable appliance tester) used to check electrical safety. Does anyone have a circuit ?

cheers

J

 

Couldn't you use an ohmmeter? What does it test?

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you could, but u need to put double the normal voltage thru the circuit (250, 500 and 1000v) for the insulation test and you need to check the earthing

 

No, it tests various things, all with either highish voltages or high currents. The UK 'Television' magazine did such a project last year.

A conventional meter would be useless.

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Nigel is correct , I haven't heard of such a thing ( believe it's a standard in the UK ) . I googled and the impression I got is that the thing measures regular V,A , load characteristics but also leakages by all supply lines to earth ( like a GFI for us Yanks) and supply VS load specs.

 

There are two test methods, class 1 (earthed appliances) and class 2 (double insulated appliances).

For class 1 you measure the resistance of the earth lead to any exposed metalwork - this should be below a specified level, and is measured with something like 20A of current - so if the earth lead is only hanging on by a thread it blows it off. You also measure leakage to ground from live and neutral, again to meet a specified level, using 500V.

For class 2 you measure leakage to any metalwork, this time using 3000V, again it must meet a specific value.

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Thanks for the info guys ! Ive not come across any circuits on the web for such a appliance.

Do you need to be a qualified electrician to certify your equipment using one of these? how can i find out? i'm a electronic engineer

 

The only one I've ever heard of was Television magazine last year, and that was fairly crude really.

I'm at work now, so I just checked our PAT tester - which is a very cheap one. It has three class 1 tests:

Normal - Earth continuity less than 0.1 ohm at 25 amps. Insulation greater than 2 MOhm at 1250V.

Long lead - Same as Normal, but earth continuity less than 0.5 ohm at 25 amps.

Soft - Earth continuity less than 0.5 ohm at 8 amps. Insulation greater than 2 MOhm at 500V.

It also has two class 2 tests:

Normal - Flash test with 3000V, leakage less than 0.25mA.

Soft - Flash test with 1500V, leakage less than 0.25mA.

It also has a button labeled "10 mA - use with caution", I'm not sure exactly what it does, but you need to press it on various items - microwaves in particular. The filters on the mains input leak and fail under a 500V test, so you need to test microwaves on a Soft test with the 10 mA button pressed or they fail the test.

All test results should be logged, including a visual inspection, test of correct plug fuse size, and confirmation that it actually works.

No you don't, I'm an electronics engineer as well, I've tested a great many items. First off you need common sense, and a good understanding of what you are testing - some items should only be given visual inspections - sticking 1250V up a computer could well damage something!.

But bear in mind, you are accepting legal liability for the item being safe, so you need to be sure it is!.

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depends. if you plan on doin this for big companies you dont work for then yes, otherwise aslong as you know what your doin you shud be ok