Gap between probe slots in handhled DMMs - Page 1
Forum section: electronics / testgear

author: atulravi
author_rank: Contributor
timestamp: June 04, 2023, 08:07:17 pm
content: Hello to all readers of the forum. I am currently working on a small device that will go inline between the multimeter and the probes which will help me get the measurements at ease. However, I would like to make the files easy for everyone to use. And it is a PCB that fits into the COM and DC voltage measuring port of my MASTECH MAS830L.I know Dave's ucurrent needs cables to be fit inline, however, I want to avoid that and want to add a banana jack that has both female and male ends which will slide on to the multimeter probe slots. The device I am working on is primarily for low end handheld DMMs which are cheap as chips and are not necessarily auto-ranging.The question is: is the gap between the ports the same on all multimeters? i.e standardised.(PS the gap between the ports in my Mastech is 1 cm from the larger hole - larger hole and 2.3 cm smaller hole to smaller hole.) I know the angling is not, however, what about the gaps?

author: coromonadalix
author_rank: Super Contributor
timestamp: June 04, 2023, 09:14:35 pm
content: i would say not standardized on some brandsi think 19mm center to center is the "standard" if i recallexamples, banana to bnc plugs etc ... bench meters psu's etc ..

author: bdunham7
author_rank: Super Contributor
timestamp: June 04, 2023, 09:27:52 pm
content: They're almost all 3/4" from center to center but the other sizes--the diameter of the center tower and the OD of the sheath hole might vary. If you are just using two plain banana plugs, 3/4" should get the job done.

author: mwb1100
author_rank: Frequent Contributor
timestamp: June 04, 2023, 10:22:46 pm
content: You are showing the distance between the A jack and the COM jack - most meters have 4 jacks and I think more often than not the A jack is farther away from the COM with an intervening jack (like a mA/uA jack). Flukes are a prime example.You might need to think about what meters your target market will likely be using. And regardless, many of your users will likely need to use cables to allow the device to attach.

author: nctnico
author_rank: Super Contributor
timestamp: June 04, 2023, 11:48:53 pm
content: Quote from: coromonadalix on June 04, 2023, 09:14:35 pmI agree. 19mm or 3/4" is as good as a standard as it gets. Power supplies and DMMs typically use this spacing between 4mm sockets / binding posts.

author: Brumby
author_rank: Unknown
timestamp: June 05, 2023, 12:47:34 am
content: Quote from: nctnico on June 04, 2023, 11:48:53 pmExactly this. ^ ^ ^Forget the 1cm measurement you have noted above - it is irrelevant to the question you are asking. To that question, the only important dimensions are the distance between centres and the size of the banana sockets.The other consideration is whether you have shrouded plugs or not - which does not change the above details. For a (near as you could get to a) "universal" solution, use unshrouded. Mind you, there are some use cases where shrouded plugs might be "specified", but unshrouded ones would still work. This can result in a reduced safety margin, but people have been working with unshrouded connections in those situations for ages. But just be aware of this.

author: atulravi
author_rank: Contributor
timestamp: June 05, 2023, 03:05:47 pm
content: I just got around to reading all of the responses and after "thorough" analysis, I will go ahead with a small box to which banana jacks can be attached to instead of a plug and play variant since clearly, the distances between the centers of the banana jacks is not standardised. That way, it will work with more meters. Thanks a lot to all of the readers who pointed out possible issues with the spacing I chose.

author: David Hess
author_rank: Super Contributor
timestamp: June 05, 2023, 05:23:53 pm
content: Quote from: mwb1100 on June 04, 2023, 10:22:46 pmMy favorite multimeters have the connectors in a triangle pattern so the mA, A, and volt-ohm connectors are all 3/4" from the common connector. Some old power supplies use this configuration also to support standard 3/4" dual banana jacks.