Questions for the electronics geeks.
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Speaking of rock solid and accurate, I measured that with my new multimeter:
The Uni-T's are very hit or miss about their input design -- some of them are probably barely adequate, others are pathetic. Considering that the design of the inputs is what makes the difference between a minor warranty repair job and this (it's a WMV vid, no onebox though):
http://gps.sozialnetz.de/global/show_document.asp?id=aaaaaaaaaaaakar
...you'll want to invest in something that's actually been independently tested and found to meet it's input Category (CAT) ratings -- CAT III is a bare minimum for use in the mains environment.
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Yeah, but I will never use it on mains. At most it might get 12v DC.
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Considering that the design of the inputs is what makes the difference between a minor warranty repair job and this
Adequate design. Not a Fluke, but it wouldn't concern me to use it on a 110v circuit if need be.
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Not great, but reasonable for the price by some definitions:
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BS1362 fuses -- these are far cheaper than 5AG/Midget HRC multimeter fuses, but while better than cheap 5x20mm or 3AG glass fuses (which are rated to interrupt a few hundred amps at 250VAC), they're still only rated for 250VAC service, vs. DMM HRC fuses which are rated to somewhere north of 500VAC/DC, and their 6-10 kiloamp interrupting rating is somewhat inferior to the 10-20 kiloamp interrupting rating of a DMM HRC-type fuse. I'd say that these'd be adequate for CAT II at most, which is where you're putting your meter anyway.
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No shunt protection (MOVs, GDTs) for voltage-based functions -- this exposes traces on the board to flashover hazards during high energy exposure. Oddly enough, the board has room for it -- maybe they initially added it, but took it off for production for some reason?
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PTCs instead of a fusible resistor for series protection on the voltage-based functions -- garden-variety PTCs aren't rated for mains service, and those that are mains-rated are designed solely to deal with modest overloads, not the higher energy of a short circuit.
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It is still better than:
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Meh, fancy schmancy PSUs. A wall wart and a USB or DC socket is normally good enough for etched boards, and we've generally used battery packs for breadboards (since you won't be running the stuff for hours on end anyway), or just wrapped copper wires around a DC jack.
$0,99 makes for a good price though.
As for multimeters, my Uni-T also is good enough, and if I ever get 500V in my design I'll have worse problems than a broken meter.
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Please make sure that you never, ever even consider using it with mains supply voltages present (>50V).
Flashover is not pretty, and if you survive one you may wish you hadn't.
Could provide links, but I've just eaten. I'm sure you can find them.
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I limit my electronics fidgeting to things that are unlikely to kill me.
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So you are not building a murderbot also?
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It is still better than:
Quite -- I'd be inclined to trust the protection on the Uni-T for basically all CAT I stuff I'd run into, and perhaps to a limited level for CAT II (CAT II 300V, maybe, as there's some evidence of input protection there). It's not a CAT III meter, but you can't get one of those for $50.
Oddly enough, there are at least some UT61s that are fitted with sparkgaps; I'm surprised they left them off the UT61E -- even a PCB sparkgap would be enough to survive the CAT II rating tests I suspect, never mind having actual gas-discharge tubes fitted ;)
As for multimeters, my Uni-T also is good enough, and if I ever get 500V in my design I'll have worse problems than a broken meter.
The issue is mains transient spikes -- switching, inductive kickback, and nearby lightning can induce several kV transients into a 240V service main. (500V steady state in the environment of an electronics project, i.e. CAT I, isn't a huge concern for the Uni-T's as that's generally a low-current source producing it.)Please make sure that you never, ever even consider using it with mains supply voltages present (>50V).
Flashover is not pretty, and if you survive one you may wish you hadn't.
I'd actually like to see how the UT61E's protection would hold up to a full CAT rating test gauntlet, both as-provided-for-on-the-PCB and as-fitted.Of course, the lack of slotting in the input traces is my other concern; they use slots in a few spots, such as the main resistor divider, but not nearly as comprehensively as say you'd find in a Fluke.
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Please make sure that you never, ever even consider using it with mains supply voltages present (>50V).
You are aware that nearly every cheap multimeter sold at Home Depot is destined to be used on an electrical panel, outlet, or switch, right? I'm sure the CPSC would move for better standards if there was an imminent risk of serious injury.
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You are aware that nearly every cheap multimeter sold at Home Depot is destined to be used on an electrical panel, outlet, or switch, right? I'm sure the CPSC would move for better standards if there was an imminent risk of serious injury.
Yeah, I simply suspect the CPSC hasn't heard enough complaints yet to have a pattern they can act on...
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I've got a similar cheap one - Toledo TMMH-930. Sees only very rare use, as I don't really do electronics stuff. I know I've used it once or twice to verify a wall socket was working, and I don't recall why I originally bought it. Possibly cause it was cheap.
Even if it selfdestructs from me using it during a thunderstorm (and why would I do that), it shouldn't be expensive to replace.
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Even if it selfdestructs from me using it during a thunderstorm (and why would I do that), it shouldn't be expensive to replace.
Well, that is not really the concern. The concern is more that it will blow up in your hand and injure you. Multimeters are cheap compared to surgery.
I do think the danger is a bit overrated. Especially for those of us who mostly do low voltage DC work. If I were working on 480V circuits every day, I would buy a $400 Fluke because not having hands would make pouring myself a drink pretty difficult.
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Well, that is not really the concern. The concern is more that it will blow up in your hand and injure you. Multimeters are cheap compared to surgery.
Yep -- one (invisible!) surge from an inductive kickback or substation switching transient later, and your meter has just gone "bang" in your hand and is emitting smoke...I do think the danger is a bit overrated. Especially for those of us who mostly do low voltage DC work. If I were working on 480V circuits every day, I would buy a $400 Fluke because not having hands would make pouring myself a drink pretty difficult.
For low voltage DC work, it's really not an issue -- the issue comes because 120/240V mains can be susceptible to surges as well; the Uni-T UT61 series, ironically enough, is likely close to meeting CAT II specs at some useful voltage rating already, but lacks any independent testing, which is the important (and costly) part of the exercise.
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As you seem to be the resident guru around here on such subjects, could you explain "counts" in reference to multimeters?
I have read a few explanations, and none of them made sense. As always, feel free to explain to me as you would to a 3 year old. ;-)
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Digital multimeters, basically throughout history, have used a type of analog to digital converter called a "slope converter" that uses a timer to measure the charging of an integrator with a known reference signal to a given point, then control the length of time the integrator is discharged with the unknown voltage applied to it.
These converters are slow, but can achieve good accuracy and good precision without the need for large quantities of sophisticated circuitry (analog or digital). So, a "count" in multimeter parlance is one increment of the least significant digit of what you're measuring.
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As you seem to be the resident guru around here on such subjects, could you explain "counts" in reference to multimeters?
Think I've got this OK..
It appears to be the number of changes/increment of number on the display before the display loses a digit of precision - i.e. when the range changes up to the next band.
For example, a 2000 count will go from 0.0v to 19.99v (2000 steps (or counts) of 0.01), but loses that last digit of accuracy on the next increment to 20.0v, since the most significant digit can only be a 0 or 1 (by dint of the fact it's a **2**000 (zero based) count)
For the next range of voltages, it'll be 0.0v to 199.9v (2000 counts of 0.1v) whereupon it will go to 200.v
Because the first digit is either a 0 or 1 , and the next three numbers only are significant, this is also known as a 3½ digit meter.
A 5½ digit meter would go 0->1.99999v, 0->19.9999v, 0->199.999v etc. so this would be a 200000 count meter.
#¾ meters can have the first digit go from 0-3 or 0-5 depending on manufacturer so a 4¾ digit meter would either be a 40,000 count or 60,000 count (0->399.99v or 0->599.99v)
Why the ½ and ¾ designations in particular for the 0-1 and 0-3/5 ranges, I've not quite ascertained...
If the first (½) is to imply that each number covers 50% of the first number's range, then I'd expect that when each number covers a 25% or 16.67% of the range they'd use #¼ and #⅙
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Between yours and @tarunik's response, that makes perfect sense and is better than all of the other explanations I have seen so far. Thanks to both of you.
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http://www.circuitspecialists.com/csi3005sm.html
I ended up not ordering this unit, as I found a breadboard power supply that filled my prototyping needs. Today, I had a chance and hopped on a steal. I picked up a dozen HP E3610A power supplies for cheap. ($20) All of them check out dead-on. I plan on giving a few away and then I will give the remainder to the guy I utilize to dump my stuff on eBay. If I can sell one of them it should cover my costs and then some.
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Sooooo....one of these also?
Kidde 21005779 Pro 210 Fire Extinguisher, ABC, 160CI
I know you weren't being completely serious, but don't get a dry powder one. If you have to let it out then don't expect to be able to use anything in the room again. As in, the powder will get into fittings and cause all sorts of issues.
Better off getting a CO2 one. The only reason that CO2 is not "recommended" is because you have to be in close proximity to put out a fire. You could put out an oven fire with a CO2 extinguisher and still eat the food afterwards - don't do that with a powder extinguisher!
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and still eat the food afterwards
Except for, you know, there might be a reason for the combustion. That food might not be what you call delicious.
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I said you could eat it, not that you would since it would be horribly burnt.
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Only thing to remember with a CO2 extinguisher is not to hold the horn to aim while discharging it, the static buildup is impressive.
I was trying to put out some very upset turbomachinery while being severely shocked which wasn't helping the situation at all.
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Only thing to remember with a CO2 extinguisher is not to hold the horn to aim while discharging it, the static buildup is impressive.
And it can get pretty cold
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Only thing to remember with a CO2 extinguisher is not to hold the horn to aim while discharging it, the static buildup is impressive.
as one who has kept my combustion in designed-for-combustion places - all right, what do you hold then?
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all right, what do you hold then?
The firefighter who told me what I was doing wrong (afterwards) said the body and the firing handle was where I should have been holding it and I wouldn't have been shocked.
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The firefighter who told me what I was doing wrong (afterwards) said the body and the firing handle was where I should have been holding it
After examining a screenful of google images... looks like there's two kinds... one with a fixed horn where that advice makes sense,
But (what I had buttumed previously) the other seems to have the horn at the end of flexible hose... in that case, it looks like most have a grip just before the horn... use that then??
TIL
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Don't hold the body, it can get cold enough to burn you as the CO2 evaporates.
Hold the handles.
If the horn is plastic with a handle, then hold that and leave the cylinder on the ground.
If there isn't a handle, then don't touch the horn.CO2 extinguishers are weird. When you start them, the fire can momentarily leap towards you, as if angry at you for attacking it.
Rather disconcerting, and totally different to other types of extinguisher.
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I picked up a dozen HP E3610A power supplies for cheap. ($20) All of them check out dead-on.
I checked them all out thoroughly tonight. The one that is the farthest out of spec is .02V positive at 8V+. Below that it is pretty much dead-on. I gave a few to my guys who enjoy electronics/Arduino?Raspberry Pi. The rest are going on eBay when I get around to it.
Good purchase, at the right time. They all came from a lab that works with pacemakers, so you know they have lived an easy life.
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Forgot this supplier (has lots of good specials):
(Marlin P. Jones Online)
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Forgot this supplier (has lots of good specials):
And they still offer an old-school dead tree catalog, which I prefer. It is a good way to find shit that I did not know I needed. ;)
Latest acquisitions:
http://www.amazon.com/gp/product/B00KS8XA2Y?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00
For my purposes, it should be more than adequate, and I believe it is the same brand that @tarunik has.
http://www.amazon.com/Tamiya-Tracked-Vehicle-Chassis-Kit/dp/B002DR3H5S
along with:
My son and I are going to pair that with an Arduino and some sensors to make a simple little rover. He is pretty cute about it. Every time we get a package I get, "Daddy, is that parts for our robot?"
Now that he is starting to read, I will get him reading code. By the time he is 5, he will probably be more employable than most recent Informatics graduates. ;)
Other than that, it has just been bits and pieces. Cords to hook banana plugs to nearly anything else. Lots of little components, etc. Resistor, capacitor, diode, etc, assortment packs. Prototyping boards and prototyping shields for the Arduino. Assortments of connectors and switches. eBay can get kind of addicting when you start in electronics.
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Nope, it's a different brand I suspect...
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http://pages.ebay.com/link/?nav=item.view&id=271659368705&alt=web
I know it is a long ahot, but does anyone have any experience with a robotic arm like this? I would be interested to know how accurate they are, how much slop is in the mechanism. I have an idea for a hobby project, but don't want to order a total POS.
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No idea. It looks well made. Paging @accalia. She's the robotics expert around here; maybe she has experience with something like it.
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That one is unbranded so I would expect lower quality than if it were branded with a known brand.
From the photo it looks decent, box aluminium is pretty strong.
No idea about the mechanism, but for that price point I would not get my hopes too high.
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Can we blacklist eBay from oneboxing? Because it's not worth it if all it's going to show is this:
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Can we blacklist eBay from oneboxing? Because it's not worth it if all it's going to show is this:
There appears to be a problem between a chair and a keyboard - using the right URL for that item produces:
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Amazon.com
