Author Topic: g'day  (Read 3114 times)

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Offline s_lannan

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g'day
« on: April 28, 2011, 06:52:35 am »
Long term electronics enthusiast turned professional technician.
Currently 3rd year into a bachelors's degree.

Boy do I have a few questions...

I bought a really cheap multimeter, still have original receipt.
DATED 20-12-2002

Followed daves multimeter reviews religiously. Bought myself a fluke 87-V.

Curious about what i bought from jaycar a long time ago.
$39.95 for QM1535.
Seemed like a really good Multimeter for the money.
Autoranging is a really handy feature.
All surface mount components except for metal film resistors.


 

Offline s_lannan

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Re: g'day
« Reply #1 on: April 28, 2011, 01:33:24 pm »
Ohh for the question.

I was expecting this thing to be built like an absolute piece of garbage!!!
It actually isn't that bad at all.
Did they get worse, was I lucky? What gives?
 

Offline alexwhittemore

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Re: g'day
« Reply #2 on: April 28, 2011, 09:44:04 pm »
Others feel free to refute, but I find that in my personal experience, the value/money curve is somewhat exponential. If you pay $10 for a meter, you can be assured that it's either EXTREMELY basic, or it's a total POS. $30, not toooo bad. $50 probably solid for light use. $100, good for light to moderate use. $1000 (think bench meter) good for SERIOUS use in a lab environment where precision matters. $10,000 (believe me, we have one at work), good when you really need every last bit: hyper resolution, accuracy measured in single-digits PPM, the real no-BS hardcore uses. But my point is that you can see the use case curve is generally linear, but the cost is log scale.

It could also well be that you just haven't been around the block enough to experience why you need a better meter than that. For example, for most of the stuff I do on a general basis, my $70 Craftsman (rebranded extech) meter gets the job done fine. But there are occasions when my new 50,000-count agilent is the only thing that will get the job done. For example, the 1┬ÁV resolution on the mV range means I get the .1PSI resolution I need when testing certain pressure transducers, so I can avoid amplification or verify amplification error.
 

Offline johnboxall

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Re: g'day
« Reply #3 on: April 28, 2011, 11:57:02 pm »
Hello s_lannan, welcome to the group.

Careful with asking about multimeters, you can start all sorts of wacky debates.  :)
alexwhittemore's response really nails it. I like Jaycar as they're still out there, however the test equipment doesn't fill me with confidence. For example, my first DMM needed a new battery - the case showed 2 x AA. Opened it up and there was a 9V.

Then in the new 2011/12 catalogue, page 14, Gary Johnston writes:
"The Digital Storage Oscilloscope that we launched last year are still going well and we've found nothing better so they are still there". So on page 25 we have a re-badged Atten ADS1022C for $599 and 1 year warranty. The Jaycar buyers must have their eyes shut or think most people are fools. If a salesperson ever offers that scope to you, go over to the bookshelf, get a Silicon Chip, and show them the Wiltronics ad selling it for $399 or the Rigol DS1052E for a bit more.

 

Offline saturation

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Re: g'day
« Reply #4 on: April 29, 2011, 05:03:50 pm »
Welcome.  One way to find out what really makes the differences between one DMM and another is doing a thorough performance check:

electrical specifications: does it meet or exceed what's published in the manual?
ruggedness: can it take the abuse a portable device will, like being dropped to the floor?
ergonomics: is it easy to use

Dave gave a sample of those, but as the accuracy and features rise, the differences are very subtle and only a through test will reveal it, so its not immediately obvious what you spend all that extra money for.  Its like getting any test gear, they look very similar up front until you push them to their limits.

Here's a sample.  Its not easy to do without the right equipment and a lot more skill doing tests.  I've been compiling this data over some weeks and its still incomplete.  Here is a preliminary result comparing them to the HP 3456a, accurate to 1uV.

Blue line = Agilent 1252a, a $430 DMM 0.025% basic DC accuracy
Purple    = Fluke 87V, a $300 DMM, 0.05% basic DC accuracy
Yellow    = Sabtronics 2035a, a 1980s circa DMM that sold for $100, 0.5% basic DC accuracy

The curves on the left are from Vdc, stretching from 30mV to 1000V
The curves on the right are ohms, from single digit to megaohms

A simple explanation is the better meter should be as close to zero as possible, that's how far off its measurements are from the reference meter. What this preliminary data shows is that the Fluke 87V markedly understates its spec sheet in these tests, as its as accurate in DC and ohms, if not slightly better, that the more accurately rated Agilent 1252a.

The Agilent still has a valid calibration certificate, whereas the Fluke 87V has not been formally calibrated in 5 years.

The Sabtronics is still within it specification limits of 0.5%, but as you can see the cheaper meter has wide swings in percentage as it moves from scale to scale, whereas the expensive meters are much 'tighter' to the reference line.


What also has been completed but not shown is how the meters perform in ambient extremes of cold, heat and humidity.   So you see, there can be much argument about whether a $50 meter is as good as $300 meter, but it won't be obvious until you do far more extensive tests than what Dave showed in his video.



« Last Edit: April 29, 2011, 05:48:21 pm by saturation »
Best Wishes,

 Saturation
 

Offline Kiriakos-GR

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Re: g'day
« Reply #5 on: April 29, 2011, 05:28:33 pm »
Careful with asking about multimeters, you can start all sorts of wacky debates.  :)


Do not afraid about me , I am holding my horses ....  ;D ;D ;D ;D

Start the damn wacky debate  :D

On topic :

Well , Saturation got all ready , at the dark waters , the ones that you find in great depths.

But I like to listen the criteria, that influence you judgment , so to describe it as
Quote
isn't that bad at all

What did you expected to see or find  ?

 
« Last Edit: April 29, 2011, 05:32:02 pm by Kiriakos-GR »
 

Offline s_lannan

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Re: g'day
« Reply #6 on: May 02, 2011, 11:08:23 am »
I was expecting to see no surface mount components at all. It seems jaycar still sell it. I guess it's done the job all these years so it'll make a good spare...
 


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