Re: Opinions about Smart Tweezers Handheld RCL Meter wrote:

>> Robert Baer wrote: >> >>> wrote: >>> >>>>I would appreciate your opinions about the following device: >>>> >>>>"Smart Tweezers LCR RCL RLC Meter Digital MultiMeter SMD" >>>> >>>>I found on eBay. Looks like an interesting concept but is it as >> >> good as >> >>>>the seller tells? >>>> >>> >>> Without a link, to look and evaluate???? >>> Forgeddit! >> >> >>
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>> >1) For the size, Priority Mail Flat Rate is $3.85; the envelope could be >distorted more by adding padding. As long as one can fit something in >that envelope and seal it, there is no limit to the weight. >Theoretically, one could ship about 42 pounds of pure osmimum (the most >dense element known). >2) ?Five? digits? Forget it. > a) Impossible for capacitors and impractical as the best accuracy one >could possibly find in an SMD capacitor might be 5%. Stray capacitance >around the probe leads can add anything from 0.2pF to 5-10pF. The PCB, >the PCB traces, and all parts in parallel with the capacitor to be >?measured? can add another 2-20pF on strays alone. > b) Impossible for non-PCB resistors; maybe 3 digits for the low values >as the probe is *not* kelvin - and maybe 4 digits for higher values to a >few megs. If the resistors are on a PCB, then there are too many parts >that can be in parallel, and the reading can me orders of magnitude off. > c) Inductors: maybe 2 digits at best in a PCB environment. The stray >capacitances mentioned previously can royally mess up readings. >3) Parts sorting - Possible; 3 digits at most. >** > Now i see their specs; the best is 1%, which absolutely KILLs 5 >digits and underscores my 3 digit statement above.

There is a difference between resolution and accuracy. Most DMMs have at least 1 more digit of resolution than their accuracy spec. The extra digits can be useful for part matching, and evaluation of tempcos and mechanical stability. Nobody needs 5 digit accuracy on an LCR meter.

Reply to
Mike Harrison
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1 more digit of

matching, and

Not true; most DMMs have an accuracy less than the digits. A typical 3.5 digit DMM has +/- 0.5% +/- 1 digit (DC voltage, the best scale). A typical 4.5 digit DMM has +/- 0.1% +/- 3 digits (DC voltage, the best scale). The HP5326/27B (5.5 digits) has +/- 0.04% +/- 1 digit (DC voltage, the worst scale, as it is made for measuring frequency or time). The B&K 5492 (5.5 digits) has +/- 0.012% +/- 1 digit (DC voltage, the best scale).

3 digits implies a possible 0.1% absolute best case; granularity makes it worse.

The photo showed a falsely stable FIVE DIGITS! Gee, maybe i can measure microns with a meter stick after all!

Reply to
Robert Baer

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