It is impossible to online buy a cheap Non-contact Direct Current voltage tester pens.

I was going to suggest you google "diy magnetometer probe" 

And this popped up 

I am skeptical... Must be a hall senor 

Thanks for posting, sorry I don't have an answer

scottiebabe  Okay.  I'll bite.  I ordered one from Amazon.  There is no Newark equivalent.  It should be here tomorrow.  3.7 stars with 25 ratings.  We'll see.

scottiebabe  Okay.  I'll bite.  I ordered one from Amazon.  There is no Newark equivalent.  It should be here tomorrow.  3.7 stars with 25 ratings.  We'll see.

anniel747 It says it does it all.   We'll see what it does and doesn't respond to.  I suspect that one of the negative reviews on Amazon was because the reviewer didn't understand that you have to have current flow to create the magnetic field in electrical circuits.  Thanks for the reminder. 

Perhaps if there is slack the cable could be taped into an electromagnet of a few turns. A few mT could be created that way at reasonably low current (e.g. 1A) although I've never tried it! 

It's useful to verify if a relay or solenoid is activated but for a simple wire there will need to be a copious amount of current to be detected.

That is exciting news! I already have egg on my face, I honestly had no idea magnetic detectors pens existed!! Built-in self test magnet included, it sounds like a genuine product. I have no clue how well it works, but I am grateful you have decided to give it a try fingers crossed it's a winner!

Beyond my budget for personal use, a railroad meter...

I have a few Triplett meters and they perform reliably. Never tested railroad so no need for the 2000.

The 3145 (60) is much simpler and straightforward.

So the ET30 arrived at 9:45pm on the day it was supposed to.  Preliminary play shows it responds to real magnets, even the fairly weak hobby magnets.  It does not respond to anything made of or resembling magnetic sheet items.  Many of my decorative refrigerator magnets go completely unnoticed.

Also unnoticed is the magnetic field of DC current - at least at levels approaching 10A.  The lowest threshold response of this detector is 63H.  Internet math says I should be able to hit that threshold at 2A with the detector on the wire.  It doesn't respond.  It doesn't respond to the current draw of my 100w amateur radio on transmit.  I could try increasing the current levels but why?  If we're at current levels exceeding 10A, I'm going for my AC/DC clamp meter.

I haven't made the time to check how small of a relay this will detect, but I am curious.  I can see where this detector might be handy in very noisy environments.  Overall, I'm not disappointed in my new toy BUT I don't think any of us are surprised that it doesn't detect the magnetic field of DC current flow.