I need to use an ohmmeter to measure the resistance between two points, and if it’s about 10 ohms do one thing, if not, do another. I’m using a basic Extech multimeter that has pointy-pointy test leads. It’s next to impossible to make contact on both points, so I’d like to jam the test leads into a pair of alligator clipsfrom Radio Shack[sup]*[/sup] and clip them on. This may be a silly question to anyone who knows anything about electricity, but will this change the measurement outcome? Change it to the point where the measurement is useless?
Broken appliances make for great learning experiences.
[sup]*I’m kind of beside myself on this one—my mall Radio Shack not only knew what they were, but had a whole draw full of them. [/sup]
As long as the connection between the probe tip and the gator clip is tight and clean, there should be no more than a few milliohms of resistance from the connection. If you were measuring very weak circuit board levels, it could screw things up, especially with capacitance loading. If you’re working with appliances where measurements within an ohm or two and a few millivolts are close enough, you’re fine.
My partner in electronics lab was the best in design and calculation.
We were told to quit using 1% resistors, so we bought 10% by the dozen, and measured out the best ones. This smart guy, best in the class, would hold the test lead probes to the resistor leads with his bare hands, thus putting 47K in parallel with the resistor he was measuring.
As he said above, you are adding an insignificant amount of resistance.
And regardless of what type of leads/clips you’re using, you should “zero” the meter by connecting the leads together before you take your resistance measurement. At this point you can either a) note the reading and subtract this reading from your resistance measurement, or b) press the relative button on your meter.
In my e-designer days, my Fluke 8020 was my prized possession… I remember buying it and using it like some people remember their first car. It was one of the ones that slowly succumbed to LCD rot, though, and I never had the time to get a replacement display. Use $10 cheapies these days that are almost as good if not as reliable and accurate. But I Remember…