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Last post Author Topic: Electric shock from USB cable  (Read 18567 times)

40hz

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Re: Electric shock from USB cable
« Reply #25 on: January 12, 2013, 05:47:54 PM »
Fluke does indeed charge through the nose for their products. But I am still of the opinion that you do get what you pay for. These things can take a serious beating before they give up and last forever when used normally.

When it comes to electronic test and maintenance equipment I agree 100%,  :Thmbsup: Fluke, Tektronix :-*, Xcelite, Jensen, BlackBox, etc. charge what they do because those who work with this stuff for a living know that, if properly cared for, most things purchased from these sources will last them throughout their career - and still be serviceable enough to give to their grandchildren once they retire.

I don't know if you always get what you pay for. But my experience is that you almost never get more than you pay for when it comes to this type of product.
 ;D

IainB

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Re: Electric shock from USB cable
« Reply #26 on: January 12, 2013, 09:36:29 PM »
Mmm, Fluke!
(Drool, drool.)

4wd

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Re: Electric shock from USB cable
« Reply #27 on: January 12, 2013, 10:42:06 PM »
Mmmm, AVO!

AVOMeter 01.jpgElectric shock from USB cable

Now, if only I could get batteries for it....

IainB

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Re: Electric shock from USB cable
« Reply #28 on: January 13, 2013, 04:57:35 AM »
Wow! That Avo meter is a real multimeter.
I actually prefer the old mirrored meter dials to digital readouts. They were ergonomically more suited to providing a relative readout, and the mirror got rid of parallax, so the reading could be pretty accurate.
I read somewhere that the Universal AVO Meter was dead accurate. What model is that one - a model 40 or something?
I presume it requires some kind of obsolete dry battery? What was it?

4wd

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Re: Electric shock from USB cable
« Reply #29 on: January 13, 2013, 05:13:56 AM »
It's a Model 8 Mk IV, it uses a 1.5V D cell and a 15V "x" cell - I can use a battery pack made of 3V lithium cells to replace the 15V, (eg. 5 x 2032).

AVOMeter 05.jpgElectric shock from USB cable

IainB

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Re: Electric shock from USB cable
« Reply #30 on: January 13, 2013, 07:21:58 AM »
Interesting. Never seen the destructions on one of those before. Thanks.

Fred Nerd

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Re: Electric shock from USB cable
« Reply #31 on: January 14, 2013, 04:50:18 AM »
I remember Jaycar trying to use a slogan of 'It's a coincidence, but it's not a fluke' for their multimeters.
Cheap analogue meters can be better in some cases since the current required to move the needle puts a draw on the circuit and can show up bad connections by the voltage drop. Sort of like using a test light and taking note of how bright it it.

Back to the printer, it's got a figure 8 plug on the printer itself (reversable, no earth), so it would be easy for an imbalance to occurr and come out through the USB cable.  I was mainly wondering if this was common since its easy to leave peripherals unplugged and the plugs in reach of kids. It could get nasty.

On electric shocks, it depends a LOT on how dry your skin is. Normal skin is about 1k ohm (enough for an autoranging meter to make make you think that you've got continuity when you hold the probes on by hand). I can't remember off hand what wet is, BUT if they are wet with salt water, it's a lot worse again.
Before LED lights, I'd go catching prawns (shrimp) with a car battery and a 50watt light. The car battery was floated in an esky and towed behind you. My original light just had the wires attached to the terminals by rubber bands. Worked fine, BUT if they accidentally came off, there was no way I could put them on with wet hands, it was very painful.

And there are no RCDs in this old place, just fuse wire so it will blow a few seconds after I'm dead to prevent the owners getting a huge power bill....

I would upgrade the printer, but I want to wait for a 3d one, then I can print business documents on fake marble carvings.

f0dder

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Re: Electric shock from USB cable
« Reply #32 on: January 14, 2013, 06:22:35 AM »
I would upgrade the printer, but I want to wait for a 3d one, then I can print business documents on fake marble carvings.
:D :-* :P
- carpe noctem

Shades

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Re: Electric shock from USB cable
« Reply #33 on: January 15, 2013, 01:53:42 PM »
The last digit on a digital measurement device is always wrong. Wrong as in not accurately showing the true value, only the approximate one.

Although analog meters do not have this problem, they have their issues as well. Normally these cannot be trusted on both the (extreme) low and (extreme) high values. Most analog meters are created to show measurement values accurately on a selected part of their full scale.

Analog car speedometers, fuel and heat gauges are famous examples of this principle. It is actually very costly to make an analog meter that works well all over its scale.

IainB

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Re: Electric shock from USB cable
« Reply #34 on: January 23, 2014, 05:06:27 AM »
It's a Model 8 Mk IV, it uses a 1.5V D cell and a 15V "x" cell - I can use a battery pack made of 3V lithium cells to replace the 15V, (eg. 5 x 2032).
 (see attachment in previous post)
__________________________
I was testing out the image-scanning OCR accuracy in OneNote (2013) and needed something meaty to test it with, so I split up the image of the back panel of your AVO meter (where it had the instructions detailed) into sections, each of which I enlarged and then scanned in OneNote. The image quality is quite good, but the back panel itself has some scuff marks which obliterate some of the text, and some of the text is a bit faint, so the result was some errors.
Anyway, here is the result, with many/most of the errors cleaned up (mostly spotted by spellcheck). I am sure I missed a few as it is otherwise a tedious manual process and I had no-one to check my work:
(You can view/download the webpage - it is "public".)
AVOMETER back panel instructions

crabby3

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Re: Electric shock from USB cable
« Reply #35 on: February 01, 2014, 12:10:16 PM »
I've experienced this can't let go and it's scary.  Screw gun on a construction site.  Couldn't let go of the trigger or open my hand.
Had to swing my arm, like throwing a frisbee, to make the tool pull away.  This was back when electric tool housings were metal and heavy.
My arm was still tingling as I stepped out of the puddle.

In retrospect I probably could have just stepped out of the puddle but it didn't occur to me at the time.  Not gonna test it.  Once is too many.
Stupidity of youth. ;D

Vurbal

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Re: Electric shock from USB cable
« Reply #36 on: February 02, 2014, 10:07:26 AM »
The last digit on a digital measurement device is always wrong. Wrong as in not accurately showing the true value, only the approximate one.

Although analog meters do not have this problem, they have their issues as well. Normally these cannot be trusted on both the (extreme) low and (extreme) high values. Most analog meters are created to show measurement values accurately on a selected part of their full scale.
This is an even bigger problem in lower quality devices when the precision ends up being more than the accuracy of the measurements.

When I was taking electronics classes I was fortunate enough to acquire a Fluke 77III. One day a friend and I decided to compare the measurements from his hobbyist meter against my Fluke by measuring the voltage drop across a diode - something in the order of a couple hundred mV. His meter gave a slightly different measurement every time and they were all at least 30% higher than the consistent number from the Fluke.

More recently I've noticed the same problem when buying a kitchen scale. Unless you find one where the manufacturer lists an 'internal resolution', you can safely assume the accuracy is equal to the precision. To make matters worse, scales made for the US market are typically accurate to a tenth of an ounce but also have an option to display grams. Of course 0.1oz is approximately 2.8g so the real precision is effectively reduced by another digit.

Sadly most people don't even understand the difference between accuracy and precision, let alone how one affects the other.

Quote
Analog car speedometers, fuel and heat gauges are famous examples of this principle. It is actually very costly to make an analog meter that works well all over its scale.

Analog meters have another problem relative to modern electronics. You can't always distinguish sudden and gradual changes reliably.
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