PATS tester circuit

[badflyer]

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

 

[Russlk]

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

 

[andrew2022]

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

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

 

[Nigel Goodwin]

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

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.

 

[TillEulenspiegel]

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.

 

[Nigel Goodwin]

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.

 

[badflyer]

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

 

[Nigel Goodwin]

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

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.

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

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!.

 

[andrew2022]

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

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