Ebay Anti-static Straps - Test First! - Page 1
Forum section: electronics / general

author: xrunner
author_rank: Super Contributor
timestamp: May 20, 2015, 03:13:14 pm
content: Just arrived from Ebay - A new anti-static strap. Of course I tested it first - andtonot to my surprise it had a complete open from the snap to the other end. I used a needle to pierce the insulation to isolate which end might be at fault, and it pointed to the snap end. I'm still cutting into it but so far there is continuity from the cut end of the wire to the entrance of the coupling. But what am I seeing there? It looks like some kind of glue - it's not solder.Be back with another pic when I get inside ...FYI the seller is sending me a new one of course.

author: Asmyldof
author_rank: Regular Contributor
timestamp: May 20, 2015, 04:27:58 pm
content: Are you sure it is an open end?ESD straps come with a 1MOhm resistor.Why?Because connecting yourself to hard ground with 0Ohm and then touching a live wire = OUCH.Being 1MOhm away from ground still does the job of you not building up floating charge compared to earth, but will not possibly kill you when you touch 300V by accident.

author: wraper
author_rank: Unknown
timestamp: May 20, 2015, 04:35:26 pm
content: Quote from: xrunner on May 20, 2015, 03:13:14 pmAll seems as it should be. 1 megohm resistor crimped to the wire (crimp looks dodgy though). I guess you need to apologize to the seller and pay for the extra ESD strap he sends to you.

author: xrunner
author_rank: Super Contributor
timestamp: May 20, 2015, 04:40:40 pm
content: Quote from: Asmyldof on May 20, 2015, 04:27:58 pmUh, yea I'm sure because my Rigol DM3058 says soQuoteWell, not this one, at least I don't see it yet. If there is an X-Megohm resistor in the circuit I haven't found it yet. So either way you slice it it's faulty. I just measured the complete cut-off coiled lead and it shows about 13 ohms from one end to the other.The fault is in the strap clip thingy but I've yet to cut into it, but I will later today.Quote from: wraper on May 20, 2015, 04:35:26 pmUh no, it's an open - see above.

author: Asmyldof
author_rank: Regular Contributor
timestamp: May 20, 2015, 04:46:21 pm
content: Quote from: xrunner on May 20, 2015, 04:40:40 pmI can literally see the resistor's butt in your picture, all bare and in view for all. Just sticking out a little from the plastic. It may be broken, or 10MOhm, what's the range on the Rigol?, by accident, but you _have_ found it.

author: xrunner
author_rank: Super Contributor
timestamp: May 20, 2015, 04:48:50 pm
content: I just cut into the cap and it's a 1 M ohm R. The crimp is dodgy, that's what the problem is. I've seen this type of construction many times before in Chinese stuff. In order find or fix it you have to destroy the thing because it's all sealed.

author: Asmyldof
author_rank: Regular Contributor
timestamp: May 20, 2015, 05:11:02 pm
content: Quote from: xrunner on May 20, 2015, 04:48:50 pmTrue enough. But at least they did add the resistor :-)

author: Ice-Tea
author_rank: Super Contributor
timestamp: May 21, 2015, 06:29:20 am
content: Quote from: Asmyldof on May 20, 2015, 05:11:02 pmyeah. I'd rather measure stuff on my bench with a broken ESD cord compared to a hard short in it.

author: mcinque
author_rank: Unknown
timestamp: May 21, 2015, 11:32:05 am
content: QuoteDon't be offended but... I really don't understand why some buy cheap chinese stuff on ebay and then complain about its quality...Probably you've paid 1$ or 2$ for that strap. What do you expect?

author: Dave
author_rank: Super Contributor
timestamp: May 21, 2015, 12:07:13 pm
content: Quote from: mcinque on May 21, 2015, 11:32:05 amThere is a difference between a low quality item and one that doesn't do its job at all.

author: mcinque
author_rank: Unknown
timestamp: May 22, 2015, 11:23:39 am
content: You're right Dave, but consider thatin a dead-simple product(as that strap), there is a very, very small difference between low quality and no quality at all (meaning useless product): you could have snaps that doesn't stay fit (= unusable product) or cable with a broken connection (= unusable product). There is no much else that can happen. So with cheap dead simple products, IMO it's a 50% win or lose game.Instead, with a DMM for example, you could have a low quality one with no input protection, slow update rate, low accuracy/precision, but that can effectively measure something.For me, that's the difference you're talking about.

author: dom0
author_rank: Super Contributor
timestamp: May 22, 2015, 11:46:34 am
content: Quote from: Asmyldof on May 20, 2015, 04:27:58 pmAnother reason for the high-resistance of ESD stuff is that it limits the bleed current ; a low-resistance ESD connection would lead to high currents that could destroy very sensitive devices (e.g. laser diodes, unprotected FETs).That's why, in my opinion, 'hard-earthed' solder station handles/tips are not ESD-safe. Also, they're just impractical for many things.