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Silicone test leads
Posted by
Jeroen3
on 16 Apr, 2018 11:26
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We've just found a dozen or so broken test leads. They're all premium brand SKS Hirschmann MLN SIL, and they all suffer the same flaw.
They break just after the plug because the insulation is flexible silicone.
So, don't buy silicone test leads I guess?
edit: Obviously these have been abused by pulling on the cable. The small plug make this very likely to happen.
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#1 Reply
Posted by
Pinkus
on 16 Apr, 2018 11:34
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my guess: this should happen only if they were frequently pulled at the cable and not at the connector.
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#2 Reply
Posted by
001
on 16 Apr, 2018 12:19
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You can see destroyed WIRE, not insulation!
So cooper sucks and silicon wins!
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#3 Reply
Posted by
noidea
on 16 Apr, 2018 13:09
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I have found something similar with Multi Contact / Staubli silicone DMM leads as well. I am using the shrouded ones with 90° and straight connector and find they always break in about the same spot at the straight connector end. My theory is that when they are plugged into test probes and are using them normally, this is the point they flex the most as the weight of the test of the lead is pulling on it. Over time the conductors fatigue and once they start to break failure becomes inevitable.
If I can find the last one I cut apart I'll post some photos.
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#4 Reply
Posted by
targit
on 16 Apr, 2018 14:03
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Same thing has happened to 2 sets of fluke leads for me, each set lasted about 5 years in daily use. Easy enough to fix with new plugs, but a real pain when they fail while trying to track down a tricky short.
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#5 Reply
Posted by
Fungus
on 16 Apr, 2018 15:41
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So, don't buy silicone test leads I guess?
Yep. Stick to PVC, it flexes much less than Silicon.
(and you'll also save some money at purchase time).
Silicon is the test-lead equivalent of putting OLED displays in multimeters - initially attractive, reassuringly expensive, but ultimately high maintenance and very short lived compared to LCD.
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right. plastic can protect metal from breaking because plastic is a lot harder than metal and metal is a lot harder than silicone, made a lot of sense.
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#7 Reply
Posted by
CopperCone
on 16 Apr, 2018 16:10
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Lol pvc test leads are mega fail. I would rather replace silicone. How can you stand pvc??
Mine are a few years old and still ok.
5 years of daily use is alot.. Not sure what you expect from the materials.. How old are your shirts buddy?
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#8 Reply
Posted by
BillB
on 16 Apr, 2018 16:24
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I think you guys should just stop swinging your meters around like bolas. Your leads may last longer.
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#9 Reply
Posted by
Fungus
on 16 Apr, 2018 16:28
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Lol pvc test leads are mega fail. How can you stand pvc??
It's not about aesthetics, they last longer because they act like springs. The whole length of a PVC lead is effective one big strain reliever.
With PVC the multimeter will move across the bench before the leads are straight enough to get a solid tug on the copper inside. Not so with silicone.
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#10 Reply
Posted by
PA4TIM
on 16 Apr, 2018 16:38
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Same here. A Pomona set within a month, Agilent set (is in all those years now around 50 cm left over) and some set I do not know the brand from. The red testlead from my Brymen 869S also within a few months. (daily use)
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#11 Reply
Posted by
CJay
on 16 Apr, 2018 17:30
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My daily drive meter has a set of test leads that are in the region of 20 years old.
Fluke Silicone.
YMMV, if you treat stuff like crap it will fail.
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#12 Reply
Posted by
targit
on 17 Apr, 2018 01:20
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I wasn't complaining about the lifespan, and as I said, simple to repair with a new connector, they always fail on the straight banana jack end for me.
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#13 Reply
Posted by
ikrase
on 17 Apr, 2018 01:41
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I wonder if this is more of a problem with strain reliefs and the exact cable layout than the actual use of silicone.
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#14 Reply
Posted by
tautech
on 17 Apr, 2018 02:20
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I wonder if this is more of a problem with strain reliefs and the exact cable layout than the actual use of silicone.
Silicone is the problem without something to extend the bending moment, it's always gunna fatigue the conductor near the end on a connector. Preformed plugs and PVC cabling
can be better in this regard.
If DIY'ing it's better to add at least one layer of heatshrink on the cable at the exit point of the connector.
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#15 Reply
Posted by
Hydron
on 17 Apr, 2018 07:46
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I've had similar issues with the Pomona silicone leads (Fluke TL71 style, which are sold with various brandings). Ended up buying another set though, as the price, usability and availability were right. The old-style Fluke leads (TL75) seem more rugged and (I recall) have slightly lower resistance, but in my opinion don't feel as nice in use due to PVC insulation.
Annoyingly some of the other Pomona products are let down by similar issues - e.g. their mini (3A) probes with replaceable tips are really useful for electronics (as opposed to electrical) work, but seem to suffer badly from high contact resistance developing between the replaceable tip and it's holder. Will need to investigate other brands in the future to try and find a more reliable replacement.
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On a side note, just the other day I came across a recent video of a UNI-T or Unitrend multimeter where at around 1:50 it showed testing of both the strain relief and fixed leads, I was rather surprised to see Unitrend going to this extent as they do not have much of a reputation in regards to quality control.
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I think you guys should just stop swinging your meters around like bolas.
Your leads may last longer.
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#18 Reply
Posted by
nanofrog
on 17 Apr, 2018 09:37
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I wonder if this is more of a problem with strain reliefs and the exact cable layout than the actual use of silicone.
Silicone is the problem without something to extend the bending moment, it's always gunna fatigue the conductor near the end on a connector. Preformed plugs and PVC cabling can be better in this regard.
If DIY'ing it's better to add at least one layer of heatshrink on the cable at the exit point of the connector.
Silicone definitely needs strain relief.
For DIY, heat shrink does a great job of it.
Personally, I find adhesive lined does even better. Particularly on larger gauge wire.
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#19 Reply
Posted by
xani
on 17 Apr, 2018 09:56
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On a side note, just the other day I came across a recent video of a UNI-T or Unitrend multimeter where at around 1:50 it showed testing of both the strain relief and fixed leads, I was rather surprised to see Unitrend going to this extent as they do not have much of a reputation in regards to quality control.
Uni-T is weird. Some of their products look well designed and generally good bang per buck, others are utter fail. And some are just straight up funny, like multmeters without enough input protection... that have PCB layout for them, just not mounted them in. Very inconsistent.
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If you're going to play the UNI-T game, may as well hit the casino tables instead with the money
It's a better gamble, and you may even win enough the one time to buy a Fluke with reliable generic leads
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#21 Reply
Posted by
Edison
on 17 Apr, 2018 22:47
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When I was working in operational research and development laboratories we used super flexible silicone cables.
When I finished my employment, I got a couple of them.
The yellow measuring cords are still unchanged - thirty years old, the isolation of the blacks measuring cords broke down after about twenty years. They are so flexible that you feel - only silicon without wires - unfortunately I can not get it anymore.
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#22 Reply
Posted by
SG-1
on 18 Apr, 2018 04:11
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If you store your meter with the leads wrapped around it, make sure that first wrap is loose, so it does not pull against the jacks.
I used to unplug the leads for storage after every shift, with my 1980s model Fluke 27, that resulted in the jacks becoming internally loose & wrecking havoc with ohm readings. I then began to leave them plugged in & wrap them around the meter. I began to experience lead failure at the jacks. Now I make sure that first wrap is loose & does not pull against the meters jacks. We will see how that works out in a few years...
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#23 Reply
Posted by
tautech
on 18 Apr, 2018 09:03
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If you store your meter with the leads wrapped around it, make sure that first wrap is loose, so it does not pull against the jacks.
I used to unplug the leads for storage after every shift, with my 1980s model Fluke 27, that resulted in the jacks becoming internally loose & wrecking havoc with ohm readings. I then began to leave them plugged in & wrap them around the meter. I began to experience lead failure at the jacks. Now I make sure that first wrap is loose & does not pull against the meters jacks. We will see how that works out in a few years...
Preformed 90
o banana jacks are perfectly suited to wrapping leads around DMM's.
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A loose first warp after following the 'angle' direction is the best way AFAIK to keep silly cone leads working
Have not lost any so far (cheapskate heaven)