questions about using an ohmmeter
Thread Starter
Burning Brakes
Joined: Apr 2005
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From: JUPITER FLORIDA
questions about using an ohmmeter
Im learning how to use a multimeter and I have a question about checking resistance. when im checking resistance with the ohmmeter it always reads 1. Now what does it mean if i check the resistance of somthing and it does not change from 1? It does not even fluctuate a little. Usually when i use it, it will either say zero or fluctuate a little.
Im getting this reading when i check my tachterminal and the cneter electrode of the ignition coil on my 86.
Im getting this reading when i check my tachterminal and the cneter electrode of the ignition coil on my 86.
Race Director
Joined: Dec 2004
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Change the range to a lower setting.
I don't know which one you have, but it should have different settings. 100 ohm, 1K ohm, 10K ohm etc.
If you have it on the 10K ohm setting, and what you're trying to measure is below 1k, it won't register.
I don't know which one you have, but it should have different settings. 100 ohm, 1K ohm, 10K ohm etc.
If you have it on the 10K ohm setting, and what you're trying to measure is below 1k, it won't register.
Safety Car
Joined: Feb 1999
Posts: 3,504
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From: Mexico Beach FL
First make sure your meter and leads are working correctly by touching the tips of the probes togther -- you should get close to zero ohms if everything is OK.
If you don't, you may have defective probes.
Tom Piper
If you don't, you may have defective probes.
Tom Piper
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
And there should be a button on the meter face for "Auto Range". When in auto mode the meter will adjust for the full scale value over many decades of values.
It's always a good idea to first check the circuit to be tested for any voltage present as such may damage the meter and will distort any resistance readings.
If you think there may be an electrolytic capacitor (tubular shaped) in the circuit, reverse the meter leads and recheck resistance as such capacitors will read differently in each direction.
It's always a good idea to first check the circuit to be tested for any voltage present as such may damage the meter and will distort any resistance readings.
If you think there may be an electrolytic capacitor (tubular shaped) in the circuit, reverse the meter leads and recheck resistance as such capacitors will read differently in each direction.
Thread Starter
Burning Brakes
Joined: Apr 2005
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From: JUPITER FLORIDA
ok i have tried everthing everyone said except switched the leads.
battery was disconnected, I tried every range setting, I use the multimeter on other things and it makes good readings, when i touch the leads together it reads a perfect zero. ???? Any other suggerstions? the multimeter is only like 3 days old too. brand new. Thanks for all the advice!
could this just mean that my ignition coil is bad? ( the car is not runninng by the way and im searching for the reason, good fuel system, new battery, new alt.)
battery was disconnected, I tried every range setting, I use the multimeter on other things and it makes good readings, when i touch the leads together it reads a perfect zero. ???? Any other suggerstions? the multimeter is only like 3 days old too. brand new. Thanks for all the advice!
could this just mean that my ignition coil is bad? ( the car is not runninng by the way and im searching for the reason, good fuel system, new battery, new alt.)
Le Mans Master
Joined: May 2005
Posts: 7,362
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From: Central Maryland
When you touch the two leads together, you'll only be reading the resistance of the leads themselves, which will be nearly zero if they're any good. So zero ohms should be expected.
It sounds as though you're reading resistances correctly when measuring other components. Sounds to me like your meter is working as it should.
Be well,
SJW
It sounds as though you're reading resistances correctly when measuring other components. Sounds to me like your meter is working as it should.
Be well,
SJW
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Racer
Joined: Jul 2005
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From: Dallas/Spring Texas
First, what are you measuring resistance on? Is it a component or is it a circuit? On my meter you have to switch it to ohms and then push a toggle button to change it to read out the ohms. I don't remember what the other function is but they (craftsman) combines two functions on the one dial position and if you don't hit the toggle then it won't read correctly. Also it would help to know what brand of meter you have.
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
OK, to test your DMM go to Radio Shack and buy one of those little packs of 4 1/4 Watt resistors, about 2.2k Ohm should be fine for testing. And pick up a bad of jumper wires, they have a roach-clip 
on either end. These are very convenient for hooking the common lead to ground while probing with the + lead.
Then you can clip the DMM leads across one of those resistors and change settings till you get it to read 2.2k Ohms.
Oh, and be sure you do NOT have it set to check "continuity".
on either end. These are very convenient for hooking the common lead to ground while probing with the + lead.Then you can clip the DMM leads across one of those resistors and change settings till you get it to read 2.2k Ohms.
Oh, and be sure you do NOT have it set to check "continuity".
Last edited by 65Z01; Oct 18, 2005 at 06:15 PM.
Thread Starter
Burning Brakes
Joined: Apr 2005
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From: JUPITER FLORIDA
I think i figured it out guys, it looks like a one but its an I for infinite. I sound stupid but it looks exactly the same as a one. If the two leads are touching nothing, it should have infinite resistance correct? when the leads are touching each other it reads 0 ohms. does this sound right? It doesnt mention much at all in the insturction manual.
Melting Slicks
Joined: May 2004
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From: Stamping Ground KY
Originally Posted by cplonner
I think i figured it out guys, it looks like a one but its an I for infinite. I sound stupid but it looks exactly the same as a one. If the two leads are touching nothing, it should have infinite resistance correct? when the leads are touching each other it reads 0 ohms. does this sound right? It doesnt mention much at all in the insturction manual.
Safety Car
Joined: Feb 1999
Posts: 3,504
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From: Mexico Beach FL
Originally Posted by cplonner
I think i figured it out guys, it looks like a one but its an I for infinite. I sound stupid but it looks exactly the same as a one. If the two leads are touching nothing, it should have infinite resistance correct? when the leads are touching each other it reads 0 ohms. does this sound right? It doesnt mention much at all in the insturction manual.
Most digital meter displays measure up to "1999" with the decimal point being able to be put anywhere. The left-most digit can only be a one ("1"). The other digits can be 1 through 9.
As an example, 1.5 volts would be 1.500 on the digital readout.
But, if the meter is "over-ranged", it will only display the left-most digit. And, since the left-most digit can only be a one, that is all you will see for an over-range condition.
So, if you have infinite resistance (which is an over-range), you will only see a one.
Tom Piper
Thread Starter
Burning Brakes
Joined: Apr 2005
Posts: 1,110
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From: JUPITER FLORIDA
Ok, ill try what you said 65z01
Tom, I think you are exactly right. I have tried every range and they all say 1 all the way on the left.
Im figureing this means my coil is bad. lets hope a new one will fix it and not waste money!
Thanks guys for all your help
Tom, I think you are exactly right. I have tried every range and they all say 1 all the way on the left.
Im figureing this means my coil is bad. lets hope a new one will fix it and not waste money!
Thanks guys for all your help
