EBME Forums Forums Maintenance Technical Assistance Practical approach to touch current testing

Well what does 60601 say about it as this is the only document that would, or should, even consider such a event?

If during the risk management assessment this fault was even considered likely then measures would be required to address it, such as making the device a class II device.

But we are going way off the original posters question now.

Of course it's likely ... I've encountered it myself a number of times over the years!

But you're right about the thread (Dave was talking about AS-3551) ... I'm finding an old 62353 one as I write (so we can continue there, if need be).

nothing new there then once GH is involved

Are you saying you didn't get the answers you were looking for then, Dave?

Interesting though the discussion on various standards is, it does not really fulfil the "practical approach" criteria of the original request. Guess I was hoping for a bit more input from those at the coal face.

Still, we live in hope.

Assuming that we are talking about routine EST, surely the "practical approach" is to ignore it altogether? As Mike has mentioned, if the kit sails through the other (current leakage) tests, how can there be a problem with "touch current" (enclosure leakage)?

Unless, as I say, you are looking at some other definition (that we are not aware of).

Unhelpful phraseology like "representative sample" can only be dealt with by making a note where (if, and when) you ever do find a "touch current" worth recording (that is, the reading that has traditionally been known as "the worse case"). And (again as Mike has said) it's up to the tech carrying out the test to decide how much time it's worth spending hunting here, there and everywhere. Just the carrying handle, the front panel, and (or) anywhere else that appears obvious, for Goodness Sake!

But I concede the point that your opening post should have warded off any discussion of (relative merits of) the various measurement methods available under IEC-62353, as it clearly states "touch current shall be measured with the equipment powered from a supply with an earthed neutral". That's why the conversation was moved to another thread.

and I thank you for it.

To answer the original question, typically we would only take a measurement at one point, and that's if you can even find an un-earthed external conductor that is accessible (a deeply recessed screw, for example, could not really be classed as accessible).

If you particularly feel the need, and if your database system allows it, add a model-specific note detailing where measurements should be taken.

Yes, "representative sample" is a poor choice of phrase (one good one should be enough) ... I wonder if it has been improved in any more recent editions of AS-3551?

I have also followed your second remark, Gordon. I recall that we sometimes even used to mark the point (screw, etc.) - with an "arrow" from a felt-tip pen, for example - where a "good" reading could be found. Also good for repeatability of results, of course.