Optimizing VOM leads

[mklotz]

I use my VOM a lot, mostly with low-voltage hobby work. I'm impatient and hate the hassle of long tangled probe leads and constantly having to change from points to pinchers to hooks. So I spent a lot of time optimizing my leads to the way I work.

The first thing was to obtain permanently coiled leads (like the older telephone handset cords) and fit them with 4 mm banana plugs at each end. With this arrangement I don't have to screw and unscrew the devices at the end of the cords as is the case with many commercially available sets. I managed to find some extra long spring-loaded hooks that accept banana plugs and a commercial set yielded some grippers with a much wider "gape" than an alligator clip.

Still missing was a set of banana probe handles that could take all the probe points I'd acquired over the years. Most of these have a M 3 x 0.5 thread.

A length of 1/4" hex aluminum from the junque boxes provided two 3.5" handle lengths. These were drilled at one end to accept a banana plug and drilled and tapped for M3 threads at the other.

I'll insulate the handles with shrink wrap if the junque box doesn't yield any suitable lengths of silicone tubing. On the rare occasions when I work with the scary stuff like 220, I have a set of commercial heavy duty leads that I use. I won't trust my homemade handles any farther than I trust the stuff that came with the VOMs.

[DIYer]

Thanks mklotz! We've added your Optimized Voltmeter Leads to our Testers category,
as well as to your builder page: mklotz's Homemade Tools. Your receipt:

Optimized Voltmeter Leads by mklotz

tags: tester, lead

[object]

A length of 1/4" hex aluminum from the junque boxes provided two 3.5" handle lengths.

There is a major downside with aluminum. If you don't immediately protect it (within seconds), the bare aluminum surfaces where the pins & banana plugs are mounted will begin to oxidize. That may change your measurements when looking at DCR or straight resistance readings. They would measure higher than they actually are.

[mklotz]

There is a major downside with aluminum. If you don't immediately protect it (within seconds), the bare aluminum surfaces where the pins & banana plugs are mounted will begin to oxidize. That may change your measurements when looking at DCR or straight resistance readings. They would measure higher than they actually are.

I don't think the effect is anything to worry about and probably would require the sensitivity of a Wheatstone bridge to detect. Nevertheless, I did an experiment to check.

I have three 50w 1% precision resistors - 10, 1, and 0.1 ohms. I measured all three of them first with no aluminum in the circuit and then with it in. These were the results...

10: 10.2, 10.3
1: 1.2, 1.2
0.1: 0.2, 0.2

[old kodger]

In the days when alloy of aluminium was used with "pop" rivets on smaller aircraft (but still commercial) we used zinc chromate between the rivets and the skin to stop corrosion of, and around, the rivets

[meyer77]

Where did you get the coiled leads?

[mklotz]

Where did you get the coiled leads?

Sorry, I don't remember where I obtained those. If you're looking to buy some, they should be easy to find on the net. Just a few minutes yielded these...

https://www.cablescience.com/coils/e...tl-series.html

https://www.mcmiller.com/6ft-coiled-...a-plugs-32846b

[kb4mdz]

I use my VOM a lot, mostly with low-voltage hobby work. I'm impatient and hate the hassle of long tangled probe leads and constantly having to change from points to pinchers to hooks. So I spent a lot of time optimizing my leads to the way I work.

The first thing was to obtain permanently coiled leads (like the older telephone handset cords) and fit them with 4 mm banana plugs at each end. With this arrangement I don't have to screw and unscrew the devices at the end of the cords as is the case with many commercially available sets. I managed to find some extra long spring-loaded hooks that accept banana plugs and a commercial set yielded some grippers with a much wider "gape" than an alligator clip.

Still missing was a set of banana probe handles that could take all the probe points I'd acquired over the years. Most of these have a M 3 x 0.5 thread.

A length of 1/4" hex aluminum from the junque boxes provided two 3.5" handle lengths. These were drilled at one end to accept a banana plug and drilled and tapped for M3 threads at the other.

I'll insulate the handles with shrink wrap if the junque box doesn't yield any suitable lengths of silicone tubing. On the rare occasions when I work with the scary stuff like 220, I have a set of commercial heavy duty leads that I use. I won't trust my homemade handles any farther than I trust the stuff that came with the VOMs.

That is awesome!!

I'll throw this out here for everyone to consider: It's possible to make your own coil cords by wrapping wire around a form, heating it gently and then letting it cool slowly. Plenty of references out there.

One caution: If you do significantly 'high voltage' be careful about choosing wire with appropriate insulation; the 'name brand' meters use a silicone rubber insulation, plus shrouded banana plugs going into the meter sockets.

At a previous job they had spools of silicone rubber covered wire, so I made myself some custom length leads; custom length coiled leads would be just the nuts!!

[jdurand]

I was once using a 7,500 V rated Tektronix high voltage probe on a 6000 V laser power supply (4kW industrial laser, not the nuclear fusion ones I later did controls for). Anyway, holding it on the wire and looking at the meter when WHAM! Smoke coming from my hand.

When I got my heart restarted I saw that I was ok but the probe had mostly gone to another dimension leaving my hand black.

So, change of pants and contact Tektronix. They quickly replaced the probe but the rating on the new, identical one was now 5,000 V. Hmmm.

I bought one of the bigger much higher voltage probes.

[Toolmaker51]

I have a bookmark file for electronics, VOM's, meggers, thermometers, pyrometers, certain unique hardware; guess what joined recently?