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Products => Test Equipment => Topic started by: tkamiya on January 05, 2019, 11:48:54 pm

Title: HP3478A banana plug incompatibility
Post by: tkamiya on January 05, 2019, 11:48:54 pm

I recently acquired a few HP3478A digital VOM. 

Oddly enough, today's common probes won't fit as the receptacles are not designed to accept sleeves around the prong.  I know the fix is to cut off the sleeves and that's what I did.  Works now.

But does anyone know the history behind this change?  Today's multi-meters all use sleeved banana plugs.  I see a logic in it that if it should come lose, it won't expose the energized terminals.  But when did this change happen?  Is there a code/law/regulation that now require this?

Title: Re: HP3478A banana plug incompatibility
Post by: GreyWoolfe on January 06, 2019, 01:01:37 am

If you have meters that use shielded and unshielded banana plug leads, these are available from Pomona.  I bought a set to try.  They are not right angle and a bit long, which for some may be inconvenient, but they work well.  I may get another set or 2.

https://www.digikey.com/product-detail/en/pomona-electronics/122506A/501-1120-ND/604315 (https://www.digikey.com/product-detail/en/pomona-electronics/122506A/501-1120-ND/604315)

Title: Re: HP3478A banana plug incompatibility
Post by: tkamiya on January 06, 2019, 01:42:57 am

Thank you. 

Any thoughts on why there are two kinds of standards?  I only use low voltage so it really isn't necessary to have extra protection. 

Title: Re: HP3478A banana plug incompatibility
Post by: 0culus on January 06, 2019, 02:19:48 am

I only work with low voltage as well (at least for the time being) so I bought a set of these for my 3455A: https://www.tequipment.net/FlukeTL940.html (https://www.tequipment.net/FlukeTL940.html)

They are very nice, and the minigrabbers are convenient for the small stuff I tend to work on. :)

Title: Re: HP3478A banana plug incompatibility
Post by: David Hess on January 06, 2019, 03:29:30 am

I do not think it is exactly required but it changed around 1980 and it did have to do with safety regulations.  Oscilloscopes probes smaller than 5mm with the 300 to 400 volt rating of the oscilloscopes they were used with also vanished at this time.

I much prefer the older style binding posts which accept an exposed banana jack, Y-terminal, or wire.

Title: Re: HP3478A banana plug incompatibility
Post by: mtdoc on January 06, 2019, 05:50:59 am

Get a set of  Probamaster probes with retractable shrouds (8018S option) (https://probemaster.com/8000-series-test-leads-only/). Excellent probes that work great with th HP3478A.