Electronics > Projects, Designs, and Technical Stuff
Community Bench Meter
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smindinvern:
I'm sort of interested in the idea of this, so, realistically, what is required to make a meter?  I imagine that conceptually it is a pretty straightforward idea.  A voltage reference and an ADC.  Compare the incoming voltage with the reference.  Use a DSP to analyze the input and do whatever you want with it, whether that's measuring the average of the input, p-p voltage, Fourier analysis, etc.  Feed it to an mcu/mpu and display it on a nice little screen.  Of course that's just voltage.  I would think current could be measured in a similar manner.  Really, as far as quality goes, what would be required to make it as high-quality as possible?  I would think basically just an extremely accurate and precise voltage reference, high-quality ADC, and measures to minimize input noise.  Is there anything (probably a lot) that I'm missing?  Because it really sounds fairly simple to me.  Simple idea, hard to pull off, I would imagine.
Bored@Work:

--- Quote from: NiHaoMike on December 27, 2010, 10:26:19 pm ---It might not be worth the effort to build a high accuracy meter or an extra cheap meter, but there are some niche applications where it makes sense.
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So, you are volunteering to fix issues a) to f) above, or ...

--- Quote ---Such as a meter that automatically calculates average and peak power. Or a datalogger that records voltages to a SD card at a sample rate of a few Hz or kHz.
--- End quote ---
... do you just want to add to the wish list?

BTW, one can get low-quality datalogging multimeters for 120 € onwards (new), e.g. http://www.unisource21.com/tDM620.html (many people allegedly have problems with it, but they will have with a DIY meter, too). Can you build one for that price?

And automatic calculation of averages and peak power can be done with any piece of rubbish that has a PC interface, plus some PC software. I never checked what the cheapest meter with a PC interface costs. I know a VA-18B can be had for 40 € (new).


--- Quote ---In any case, we'll make the assumption that the accuracy needed is comparable to or less than that of the under $20 meters and that the builder already owns a meter (and calibration reference) much more accurate than the one being built.
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That excludes all those who were after a high-precision meter for next to nothing.


--- Quote ---One extremely high accuracy measurement that is relatively easy to make is time/frequency. Put a GPS in your homemade frequency counter and you'll very likely have more accuracy than you'll ever need.

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1) What has that got to do with a bench multimeter?
2) The guys on timenuts would disagree with "GPS in your homemade frequency counter and you'll very likely have more accuracy than you'll ever need".
Bored@Work:

--- Quote from: smindinvern on December 27, 2010, 10:38:33 pm ---I imagine that conceptually it is a pretty straightforward idea. 
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Then do it. Don't talk, do it.
smindinvern:

--- Quote from: BoredAtWork on December 27, 2010, 10:55:35 pm ---
--- Quote from: smindinvern on December 27, 2010, 10:38:33 pm ---I imagine that conceptually it is a pretty straightforward idea. 
--- End quote ---
Then do it. Don't talk, do it.

--- End quote ---

Could you be a little bit more helpful?  I'm interested in learning as much as I can.  This forum is a treasure trove of knowledge.  That's why I asked.  My education certainly isn't your responsibility, but any help you would like to offer would be appreciated.
Bored@Work:

--- Quote from: smindinvern on December 27, 2010, 11:01:29 pm ---Could you be a little bit more helpful?
--- End quote ---

Why? I owe you nothing.  Let me tell you a little story. It is the story of why I don't have a ham license.

When I was a boy ((C) Dave Jones) I was at some point in time very interested in amateur radio. So I started to study for a ham license. I memorized all the abbreviations, operating procedures and stuff. I even started to learn morse code, taking a course. This was the time when you only got a serious license if you knew morse code. I was about to become better, almost to the point that I could do morse.

And then, via the morse code course, I started to make contact with hams in the local amateur radio club. These OMs (see, I can still do the ham lingo) were all the same. They were always talking about the great things they plan to do, and what they would build and how great hams are, how special, because they build their own stuff. Yes, they do. Licensed by the government, no less.

But when visiting their shacks it was always the same. There was just commercial equipment on their benches, and somewhere in a corner was a half-finished project. Often literally covered in cobwebs. They all had their unfinished alibi project, but nothing else. They just talked, often about things they didn't really understand, because their technical ham training was in fact poor.

It was deeply disappointing. And I dropped the morse code course and stopped studying for a license, because I never wanted to be like them. Only talk, no do. Many years later, at some point in my EE career, I was operating RF equipment every ham would go apeshit about. Of course no ham license needed, and it gave me deep pleasure to remember these poor "we are so great, we are hams" guys with their cobweb projects.

And since the days of my aborted attempt to get a ham license I despise people who always talk, but don't do. Who wank about how great some project could be - if just others would do the work. They are time wasters.

Unfortunately, this type of people have become more ubiquitous in recent years. Scratching their private parts, grunting "uh, cool, eh, eh, eh", feeling entitled, and shouting "awesome" is all they do. I have seen many such "projects" like this one. Someone shouts Wouldn't it be great, if ...?, and the wanking croud responds Cool, you are awesome dude! You are the man! And it must have .... Of course non of them lifts a finger to actually do something.


--- Quote ---I'm interested in learning as much as I can.  This forum is a treasure trove of knowledge.  That's why I asked.  My education certainly isn't your responsibility, but any help you would like to offer would be appreciated.
--- End quote ---
You just got an education. Don't talk, do, especially if you think

--- Quote ---it is a pretty straightforward idea.
--- End quote ---
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