8
\$\begingroup\$

What is the practical benefit from very sharp probe tip and fast continuity test of multimeter?

I was searching for a while with google and in ee.se but results contain mainly a dmm seling ads with featuring sharp tip probes or similar. Maybe can't find correct search keywords, but can't find this question answered here too.

In EEVblog, Dave Jones mention quite few times importance of fast continuity test, but only once give the example with faster and more convenient way to test multiple pins on a IC. Fair and square, but only applying in electronics. That disperse the fog a little but I remember a friend of my father talking something similar and I am quite sure he was in electrician. On top of that IC weren't that prolific at that time at all.

Sharpness of the tip, I can rationalize that albeit having smaller area of contact, probably give you better mechanical contact in practice, specially if probe make miniature dents in softer metals. Easier to penetrate very tin layers of oxidation or other impurities. Electrical current like to flow from sharp pointy surfaces better and flat, but not sure how that translate into practice with much more less that kV range (U<30V) and no arcs.

Is there more than just psychological point of view mine is better because is (bigger, faster, sharper, stronger etc.)? How blunt is blunt and how sharp is sharp actually? If there is practical difference is it noticeable? Is it possible to be quantified?

\$\endgroup\$
  • 6
    \$\begingroup\$ Fast continuity test is a boon when trying to map out an unknown wiring harness - some DMM's are slow enough that you can't "wipe" down a header but have to purposefully try each pin, which can be quite annoying. \$\endgroup\$ – Chris Stratton Jan 3 '13 at 15:29
  • 1
    \$\begingroup\$ Some probes are sharp enough to penetrate insulation so that you can test the wire inside without leaving a gaping hole. Also useful for probing into a connector to reach the contact inside. \$\endgroup\$ – Dave Tweed Jan 3 '13 at 15:58
  • 1
    \$\begingroup\$ @ChrisStratton: One thing I'm surprised I haven't seen more widely promoted is a continuity/voltage-probe beeper. Such a device can be easily constructed so that the pitch of the beep varies with resistance, or can be used to generate a pitch which varies with voltage (so if a pin which usually outputs a constant voltage changes, it can be instantly heard, or so that if many pins have the same voltage but one is different, probing the pins will reveal the oddball). \$\endgroup\$ – supercat Jan 3 '13 at 18:01
8
\$\begingroup\$

Sharp tips are able to poke through insulation, whether it be wire insulation, or the coatings on circuit boards. They are also handy if you need to stick it down into a connector between the wire and the body of the connector. Also, as parts get smaller, you need sharp tips to be able to contact one pin of an I.C. without shorting to the others. Lastly, a sharp point isn't as likely to slip when you look away to read the meter. The flow of current from a point isn't meaningful here because that's only relevant when there's an air gap present.

The response time of the continuity "beep" is important. If you want to test a number of contacts--especially if you're hunting for that one signal in a large set--you want to be able to do it fast. Otherwise, you have to touch the wire, then wait, then move on. It's very unsettling when doing continuity checks to have to rely on the notion that "it didn't beep, therefore there's no continuity". Did I wait long enough? Did I actually contact the wire? This is why you start by touching the meter leads together to be sure the beeper is actually working.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.