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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / February 2005question about reading an Ohmmeter
Hi, I was checking spark plug wires with my ohmmeter and just want to make sure I know what I am looking at: When I set my meter at 20k ohms and measure an 18 inch plug wire, one wire reads 1.09 which I interpret to be 10,900 ohms which would be ok at 10,000 ohms resistance per foot. Another 18 inch wire reads 44.50 which I would assume is 44,500 ohms, which would be too much resistance for a "good" plug wire. Am I reading the meter right? Thanks, Libby You are reading it right, time for a new set of wires. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's > Hi, > I was checking spark plug wires with my ohmmeter and just want to make [quoted text clipped - 8 lines] > Thanks, > Libby The 1.09 is my old wire, the 44.5 is a brand new Auto Zone wire. I think it is bad right out of the factory, if I am reading the meter right. You need to compare oranges to oranges and apples to apples. In other words compare the new length to another new one. 'Sets' of wires vary radically for resistance's between 'sets', but all in the set are the same per foot. If one in the set is different per foot than the others, then yes you have a bad one right out of the box. It does happen. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's > The 1.09 is my old wire, the 44.5 is a brand new Auto Zone wire. I > think it is bad right out of the factory, if I am reading the meter > right. The 1.09 means 1.09 K or 1,090 ohms. A 10,900 ohm reading would be 10.9 just as your 44,500 ohm reading is 44.5. Multiply the displayed number by 1000 to get these values. When I don't know the value of a plug wire, I measure a few to get the gist of what I'm looking at. A 12 inch wire reads one thing, a 24 inch wire is twice that (or should be) and so on. An 18 inch wire would be between the two values etc. My meter has dial settings: 1K, 20k, 200k, etc. Do these mean to move the decimal place on the displayed value, the number of zeroes in the dial setting, to get the actual reading? So that with the meter set on 20k a reading of 1.09 would actually be 10.90? > My meter has dial settings: 1K, 20k, 200k, etc. Do these mean to move > the decimal place on the displayed value, the number of zeroes in the > dial setting, to get the actual reading? So that with the meter set on > 20k a reading of 1.09 would actually be 10.90? No.. the decimal place would move if it wants to display 10.9k ohms. 1.09 is 1.09k ohms. Wait. Is this an analog meter? If it's an analog meter, you are reading it right. 1.09 is 1.09K on those types of meters. You more than likely bought resistive wires. They have resistance purposely. Compare all the wires, see if they make sense with each other (from the same set). I dont think they are bad. >My meter has dial settings: 1K, 20k, 200k, etc. Do these mean to move >the decimal place on the displayed value, the number of zeroes in the >dial setting, to get the actual reading? So that with the meter set on >20k a reading of 1.09 would actually be 10.90? There should be a symbol somewhere on the display, if you're in the kilo ohms range you should see a "k" if you're in the Mega ohm range, you should see an "M" if you're in the single ohms stage, you should see the Omega sign While 20K indicates full scale, anything over that will show up as infinity/overload any integers will show up as Kilohms so at the 20k reading of 1.09 you are reading 1.09 kilo ohms one thousand ninety ohms All is clear? Lg > Hi, > I was checking spark plug wires with my ohmmeter and just want to make [quoted text clipped - 8 lines] > Thanks, > Libby Is this a digital or analog meter? I take it if you are reading to three digits it is a digital. In that case, it seems to me that 20K ohms would be the limit, so you must be reading 4.45K ohms. If it is an analog, then the 20K ohms scale would indeed read that high, and you might indeed be reading 44.5K, but it would be hard to say without actually seeing the scale- it is sort of a log scale, and shows several decades worth of values. |
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