Test Leads, the ultimate choice - Page 1
Forum section: electronics / general

author: mendip_discovery
author_rank: Super Contributor
timestamp: August 30, 2021, 05:15:10 pm
content: What test leads should people have for the different types of measuring? Other than the "buy the XX brand" what leads do people prefer for specific measurements. I ask as theHow do you Test your cables?post made me think of what test leads one should have in the labAt work, I have a plethora of wires and leads but I will admit I don't trust some of them and I would love to delve deeper into the world of what makes the ultimate test lead for x or y task. I have looked at some of the solid core Cat-5 cable I have at work and wondered if I could use the twisted pairs to make some nice shielded cables for low DC and Resistance measurements.I have attached a document I received that makes some basic comments about the connection choices from Wavetek just for general consumption.MeasuringConnection TypeLinkCommentsResistance4-Wire Clip ConnectionsFranky's Kelvin Clip Kit, also seeKelvin Clips recommended as they insulate both top and bottom connections.Resistance2-Wire Clip Connections??Resistance4-Wire Banana Connection??Resistance2-Wire Banana Connection??ResistanceHigh Resistance Connections??Capacitance[td ?] ?DC Volts>1000V ? ?DC Volts<1000V ? ?DC Volts<1V ? ?AC Volts>1000V ? ?AC Volts<1000V ? ?DC CurrentuA ? ?DC Current<20A ? ?DC Current>20A ? ?AC CurrentuA ? ?AC Current<20A ? ?AC Current>20A ? ?FrquencyBanana to BNC ? ?FrquencyBNC to BNC ? ?

author: mendip_discovery
author_rank: Super Contributor
timestamp: August 30, 2021, 05:30:23 pm
content: For example, ignoring the crap choice of crock clip (its for illustration), where would you attach the two wires for a 4 wire resistance measurement set-up onto a 2 wire connection.Do you connect Sense and Source wires to A, or A and B, A and D, B and C?Would there be a design choice of crock clip one should look at?

author: rigrunner
author_rank: Frequent Contributor
timestamp: August 30, 2021, 06:26:30 pm
content: Personally I wouldn't bother with that setup.If what I'm measuring needs 4 wire I'd use a kelvin clip. Nothing fancy, a set from Franky works fine.https://www.eevblog.com/forum/testgear/franky_s-kelvin-clip-kit/If you need clips for small stuff there is a user on here, Robrenz, that made a exquisite set of tiny kelvin clips and videoed the process.

author: Gyro
author_rank: Super Contributor
timestamp: August 30, 2021, 06:29:11 pm
content: Quote from: mendip_discovery on August 30, 2021, 05:30:23 pmFor 4 wire resistance measurement (also known as Kelvin connection) you need specific Kelvin clips. These have the two jaws of the clip electrically isolated from each other - not connected by the metal hinge pin or spring.With Kelvin clips, it is a simple matter of connecting the source wire to one jaw and the sense connection to the other jaw of each clip. You don't have any issues of where on the jaw you make the connection ( your image) because the source and sense connections only occur at the single points where the jaws contact the component lead.A typical example...

author: magic
author_rank: Super Contributor
timestamp: August 30, 2021, 06:44:27 pm
content: So that's what they are forI own one (and exactly one) such clip. It was bundled with some meter supposedly as means of testing small SMD passives. Of course it doesn't work very well because the spring is much too strong and sends the components flying far awayI have always simply used two pairs of clips for 4 wire measurements. Seems obvious enough. I wouldn't trust a full metal clip with two wires connected anywhere, you have no control over where the test current flows.

author: bob91343
author_rank: Super Contributor
timestamp: August 30, 2021, 06:45:42 pm
content: For very little money I purchased a set of 'Kelvin' clips from China. Strictly speaking, these are not Kelvin clips but that's what everyone calls them. The clips are poorly designed and don't clip securely so I put some solder on the jaws that seems to help. I have them almost permanently connected to my HP 3456A.A better design would be welcome but probably would be expensive.

author: Gyro
author_rank: Super Contributor
timestamp: August 30, 2021, 07:15:20 pm
content: Quote from: magic on August 30, 2021, 06:44:27 pmActually, that's the preferable method - if you want to be really accurate, then you want single point connections (not randomly spread across the width of the jaws), so you would put the source clips further out on the leads and the sense connections (preferably knife edge) at the exact component lead lengths of interest.In practice, these clips are just there to get rid of the test lead resistance contribution on low resistance measurements, so it's pretty academic whether you use 4 single clips or 2 Kelvin clips [Edit: in all but the most precise use cases!].

author: notfaded1
author_rank: Frequent Contributor
timestamp: August 30, 2021, 07:17:12 pm
content: For upgrading my DE-5000 I created a set of modified kelvin clips for mine replacing the tiny clips that came with it. I bought an extra module that plugs on the front and modified it like in this video:Bill

author: figurativelythedevil
author_rank: Contributor
timestamp: September 18, 2021, 09:43:11 pm
content: Based on this thread I decided to design an adapter for using coaxial 4-wire kelvin clips with banana jack multimeters! I made a thread here in the forum and an imgur post with a bunch of photos and commentary. Sadly I have to wait until Tuesday to test it as the kelvin clips I ordered are still in the mail! Let me know what y'all think. I'm pretty new to a lot of metrology concepts so it's possible I've made some huge mistake with this thing, but I had fun designing and building it!Forum post:https://www.eevblog.com/forum/projects/banana-jack-to-coaxial-4-wire-kelvin-clip-adapter-board/Imgur Album w/ Hi Res & commentary:https://imgur.com/gallery/B6nNp7m