| Electronics > Beginners |
| Yet another what DMM should I get thread |
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| rsjsouza:
--- Quote from: exe on June 01, 2018, 02:20:35 pm --- --- Quote from: rsjsouza on June 01, 2018, 02:15:44 pm ---On a side note, a frequency meter can also be much more accurate than the one built into an oscilloscope. --- End quote --- Why so? Anyway, I don't think this applies to cheap DMMs in this thread. --- End quote --- Well, that always depends on the oscilloscope in question. Some use the information on the display buffer to measure frequency, while others use a fast hardware counter to do so - the latter is usually much more accurate. With DMM or external frequency meters the scenario is similar; because of their implementation is done via a fast counter implemented in hardware, they tend to be quite accurate. The Aneng 8009 (and several other cheapies) have a built-in frequency meter. |
| rstofer:
--- Quote from: Discotech on June 01, 2018, 03:21:32 pm ---The Cat 1 & 2 confuses me on grey areas --- End quote --- The ratings have to do with impulses on electrical systems. The idea is that you might be using a DMM to fix your dishwasher when a lightning strike hits your incoming mains. I have made it a practice to avoid working during lightning strikes and since there are only about a dozen air bursts per year around here, it just hasn't been a problem. In industry, other things might cause an impulse but at the same time, other devices on the power system help clamp the effect. I can see where capacitor systems might be an issue but they just aren't the kinds of things I plan to work on. The higher the CAT number, the closer you are to the lightning. Once you are beyond the wall outlet, the CAT ratings might not be terribly important unless you are working on high voltage power supplies. I don't do that so no worries. Even then, energy is usually limited. I'm pretty certain that driving to work is far more dangerous than a bogus CAT rating. http://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf There are a number of ways to hurt yourself with a DMM, or any other tool for that matter. If you want a guarantee, buy a toaster. |
| joseph nicholas:
Since you have posted into the beginners section I would recommend you reconsider the second meter be more expensive than the cheap one you already own. To shift the original subject matter. Why not consider an anolog meter as your second choice. I say this for those reading along and in your situation. |
| exe:
--- Quote from: rsjsouza on June 01, 2018, 03:39:29 pm ---Some use the information on the display buffer to measure frequency --- End quote --- Why is this bad? What's on the screen is clocked from the internal source. I can image due to jitter and noise, etc it won't be precise down to a few ppms, but I don't see why this should be horribly imprecise. Just be sure there is at 5-7 rising edges on the screen so it can do the math properly. I can give one datapoint :). I actually compared both ways (hardware counter and software counter) on my TO1104 about a year ago, both agreed with what my signal gen claimed (new sdg2042x with cal cert, afaik). |
| Discotech:
--- Quote from: rstofer on June 01, 2018, 04:07:26 pm ---The ratings have to do with impulses on electrical systems. The idea is that you might be using a DMM to fix your dishwasher when a lightning strike hits your incoming mains. I have made it a practice to avoid working during lightning strikes and since there are only about a dozen air bursts per year around here, it just hasn't been a problem. In industry, other things might cause an impulse but at the same time, other devices on the power system help clamp the effect. I can see where capacitor systems might be an issue but they just aren't the kinds of things I plan to work on. The higher the CAT number, the closer you are to the lightning. Once you are beyond the wall outlet, the CAT ratings might not be terribly important unless you are working on high voltage power supplies. I don't do that so no worries. Even then, energy is usually limited. I'm pretty certain that driving to work is far more dangerous than a bogus CAT rating. http://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf There are a number of ways to hurt yourself with a DMM, or any other tool for that matter. If you want a guarantee, buy a toaster. --- End quote --- It seems like cat ratings then are more suited towards actual electrical engineers in industry doing proper electrical stuff rather than aimed towards hobbyists who are only tinkering (unless they get adventurous and decide to rewire their home ?) So am I safe to assume for the sort of things I'll be doing (starting off with at least) the Anengs will be capable enough and if/when I want to move to more complex and higher voltage than what you'd find in synths then that is the time to move to a more expensive bit of gear ? --- Quote from: joseph nicholas on June 01, 2018, 04:29:08 pm ---Since you have posted into the beginners section I would recommend you reconsider the second meter be more expensive than the cheap one you already own. To shift the original subject matter. Why not consider an anolog meter as your second choice. I say this for those reading along and in your situation. --- End quote --- How much more expensive is acceptable bearing in mind the current one I own only cost about £10 ? |
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