Powerful and Portable DMMs For 2008

摘要

What features does your present DMM lack? Have you found a meter in the comparison chart that would do your job better? Chances are that unless your DMM is relatively new, you can buy more performance at a lower cost today. Nevertheless, perhaps it's also never been more difficult to buy a DMM or at least to decide which one to buy. As occurs in all test instruments, features migrate down from high-price meters to lower-cost DMMs each year. As the comparison chart shows, apparently similar feature sets can have a relatively wide range of prices. Sometimes you are paying a premium for a manufacturer's reputation. You might find that it's money well spent should you need a DMM repaired or replaced under warranty. Other times, a lower price may indicate a less expensive implementation of a feature and perhaps a less useful one. Now that there are so many features packed into virtually all DMMs, you must consider many more details than just basic voltage or current accuracy. How does the accuracy of the AC voltage reading vary with AC frequency? Even if you only work with 50/60-Hz systems, how accurately will your DMM measure higher frequency harmonics? Unfortunately, there is a direct correlation between the size of a DMM's datasheet and its price. If they both are small, you may not be able to answer questions about more obscure specifications such as crest factor. It's not listed. A more complete datasheet usually goes hand in hand with a higher-performance meter. So, what does the future hold for DMMs? Certainly, there will be even more features available next year and for years to come. An idea of what they might be follows from looking at how other types of instruments have progressed. For example, several models of DSOs now can extract only unusual waveforms from the millions presented. How about a smart DMM with a similar exception recognition capability?