Modular multimeter probes or DIY probe tips? - Page 1
Forum section: electronics / projects

author: mlamoore
author_rank: Newbie
timestamp: July 25, 2023, 01:23:27 pm
content: I've seen a multimeter with replaceable probe tips: the probe tips were just thin rods with a pointed end that slid into metal tubes in the handles/leads.Does anyone know what I'm talking about?I want to buy (or make) something similar for a DIY probe project.I frequently use standard oscilloscope probes with the spring clip removed and the ground lead replaced with a ground spring, so the pointed tip of the probe rests in a large via and the ground spring rests in any nearby ground via. This gets much better signal quality than using the ground lead, especially in power electronics projects. The probe will even balance this way under its own gravity, allowing me to set up many measurements hands free with very short ground connections.I want to make a DIY differential oscilloscope probe that can rest on vias in a similar way. I'm envisioning a narrow PCB with an amplifier under a metal EMI shield and two contact points for contacting vias to measure them. To account for different via sizes and spacings, I'd like to have replaceable tips that I can bend into different shapes for different measurements: straight, with a small kink, or with a large kink (and short to minimize loop area or long for harder to reach parts of the board or to get more probes to a small area).My understanding is that multimeter probe tips are often made of tin coated steel but are occasionally gold coated; is the same true of oscilloscope probes? Is anyone aware of somewhere I could buy thin pointed rods of a material that would be appropriate for this application?Or is there a material that could be appropriate for use as a probe tip without any coating, so I could just buy a rod, cut it into lengths, then add points with a bench grinder?All the googling I've done has just gotten me places to buy complete probes, but I'm just looking for simple replaceable tips.

author: tooki
author_rank: Super Contributor
timestamp: July 25, 2023, 05:48:44 pm
content: I was confused for a moment, since the opening sentence and thread title talks about multimeter probes, then the third sentence talks about "standard probes" but it then becomes apparent you're talking about oscilloscope probes...Anyhow:Quote from: mlamoore on July 25, 2023, 01:23:27 pmI assume you mean precision multimeter probes like the Fluke TL910 (aka Pomona 6341/6342/6275) or Probe Master 8050? Both of those have a pogo pin receptacle into which pogo pins are inserted to function as probes. The TL910 comes with both gold-plated pogo pins and rigid unplated stainless steel needles. The Probe Master used to come with both gold-plated pogo pins and rigid gold-plated stainless steel needles, but they no longer include the rigid needles (nor appear to sell them as spares anymore).Quote from: mlamoore on July 25, 2023, 01:23:27 pmSounds to me like you're basically trying make something mechanically similar to the Positioner Tip of the LeCroyDX20-PT-KIT. (And knowing LeCroy's probe pricing, that probably cost thousands and thousands...)Quote from: mlamoore on July 25, 2023, 01:23:27 pmNo. They're usually either brass plated in nickel or gold, unplated stainless steel, or gold-plated stainless steel. Tin tarnishes readily and would make a terrible plating.Quote from: mlamoore on July 25, 2023, 01:23:27 pmI believe they're the same as multimeter probes. The LeCroy Adjustable Tip tips are nitinol, according to the datasheet above.Quote from: mlamoore on July 25, 2023, 01:23:27 pmStainless steel, as seen above.Quote from: mlamoore on July 25, 2023, 01:23:27 pmPomona sells just the replacement tips for the TL910/6341/6342/6275 as model number 6354 for the complete set. (They used to sell the stainless needles alone as 6213 for short ones and 6214 for long ones, but that's seemingly discontinued.) In either case they're 0.040" diameter.Also, take a look at LeCroy PK1-5MM-104. I don't know the shaft diameter, however.

author: mlamoore
author_rank: Newbie
timestamp: July 25, 2023, 06:39:54 pm
content: Thank you very much! I'm pretty sure the TL910 stainless steel tips are exactly what I'd seen that gave me the idea.That LeCroy system looks very nice! Yeah, I'm basically envisioning something like their Positioner Tip, but using a pliers to bend a set of stainless steel needles into different shapes (and rotating them in the pogo receptacle) instead of their thumbwheel mechanism.I updated my post to add the word 'oscilloscope' a few times to make it more clear.I think the Pomona 6354 tip set looks like exactly what I want to use, now I just need to locate a brass tube or pogo receptacle with a 0.040" I.D. (And thanks for pointing out that pogo pins have exactly the sort of receptacles I need.)

author: tooki
author_rank: Super Contributor
timestamp: July 26, 2023, 01:22:24 am
content: Quote from: mlamoore on July 25, 2023, 06:39:54 pmHarwin S19-501 is designed specifically for 0.04" (1.01mm) pogo pins:https://www.harwin.com/products/S19-501/But 0.040" is also exactly the size of a size 20 contact, like what's used in D-sub connectors and countless military connectors, as well as various PCB pins and sockets. There's a massive selection of stuff on the market in that size. I'd prowl around the Mill-Max website or catalog, as well as the PC Pin Receptacles section of connectors on Digi-Key.There also exist 1mm pin jacks in the test and measurement world (like Stäubli EB1).

author: mlamoore
author_rank: Newbie
timestamp: July 26, 2023, 02:35:03 am
content: Thank you again!I'd already found DigiKey's 'Test Probe Tips' section which has the similar but too large S25-512 and other related parts, so that's where I was looking without finding S19-501 (under the generic 'Test and Measurement Accessories').I'd also found the TE Amplimite HDP-20 size 20 contacts and was planning on buying a few different candidates from 'Contacts > Multi Purpose', but now I'll definitely try that S19-501 too.