CEM DT-9939 multimeter leads (WHL #88)

Just an oddball thing that I discovered this week when lending out the leads of my newest multimeter, a CEM DT-9399. While the unit was an absolute bargain for what it can do, and the only thing to complain about is the slow continuity test mode and the slow Wireless USB (!) data transfer, this post really is about the boring leads. They just happened to be the only ones around in the office, and the boss asked for a spare multimeter that he could take home for the weekend for some rudimentary electrical testing, likely on an AC device. Well, better safe than sorry, don’t hand over the regular (non-safety) 4mm leads with some add-on test prods – give him the leads that came with the 1000V CAT III/600V CAT IV meter, right?

Well, those fuckers are proprietary. They don’t fit any other meter, I’ve checked quite a few. But they look like regular leads…

Since I actually haven’t found specs of safety 4mm leads (well, except for the 4mm pin part, d’oh!), let’s compare some that I have accumulated over the years.

MC branded ones, I’ve saved these from the bin (someone snipped off 8 of these for soldering one side to a test fixture). I just bought new 5m silicone wiring for each pair and keep these for the unusual stuff that doesn’t work within a 2m radius from the main lab power supply.
Inner diameter of the safety collar: 6.54mm, outer diameter: 7.95mm (I’ll just give you the raw readings, these likely carry an uncertainty of ±0.1mm, if not more)

Greenlee leads, from my main 500000 count DM-860A = Brymen 869s meter. ID 6.52mm, OD 8.00mm

Peaktech leads, from my first “real” manual range 2010DMM unit. Clearly not the original color anymore. ID 6.57mm, OD 7.95mm

Aneng leads, from an AN8008 pocket-sized unit that I actually used a lot before the humongous Greenlee showed up. Super short leads as well. ID 6.70mm, OD 7.93mm

And now, those scumbag leads from CEM. ID 6.05mm, OD1 (small part on the bottom) 7.69mm, OD2 (across the two ribbons that allow a snug fit in the CEM meter jacks): 8.84mm!

Recap: (this newfangled “table” rubbish doesn’t seem to be supported in good ol’ WordPress?)
MC: 6.54mm, 7.95mm
Greenlee: 6.52mm, 8.00mm
Peaktech 6.57mm, 7.95mm
Aneng: ID 6.70mm, 7.93mm
CEM: 6.05mm, 7.69mm-8.84mm

I’ve filed down one of them, the outer diameter isn’t the issue for regular multimeter jacks. It’s clearly the narrower inside of the barrel that causes the issues, which means the CEM meter likely uses a very thin separator ring that might be prone to premature failure. The meter fits regular 4mm banana jack connectors just fine by the way, only the stubby Aneng ones wobble around a bit.

Well, those CEM test leads go to the bin, I suppose…why the fuck would one even make noncompliant test leads or source oddball banana jacks for the meter that fit these? I don’t get it…

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