Multimeter resistance question

[Wow1420]

The resistance measurement on my PVs seems to always be within .1 ohm of each other and my good DMM. That's good enough for me (never sub-ohm).

I got one of those HF cheapies free with some other purchase. It's pretty much useless for anything but checking batteries. I'd never trust it for anything like coil building, it's wildly inaccurate at low resistance measurements.

 

[edyle]

First, I hope this is an OK place for this thread. I have no idea why, but I am unable to post in the New members forum, which is where I originally intended to put this. I seem to be able to post in any other forum but there. So, anyone have ideas on that?


I bought a cheap Digital Multimeter at Harbor Freight. (I know, buy cheap...get cheap results). My thought process was that I could use a digital multimeter anyway, and it would be a good "double check" of ohm resistance if I ever step up to a regulated mod that has the resistance tester on it. I plan to do some coil building soon. So, I wanted the baseline resistance and touched the lead tips together and it was all over the place. I tried it a dozen times, and was very careful to hold them steady. It finally settled on 1.2 ohms. Is that crazy? I thought the typical baseline resistance of the leads was usually in the .02 to .05 ohms range.

I think the thing is just junk and should be returned...which I am going to do. But, do I need to spend $30 to get a decent one that will be accurate on resistance testing, or have others been using cheap multimeters with good results? Am I just unlucky?

Thanks.

That sounds like my cheap multimeter. Some days it's like 2 ohms, some days it's 1 ohm ; you check that value first then do your measurement and subtract.

I recently bought another multimeter, because the cheap one I'd been using uses a 1 in long 12 volt battery which it turns out is hard to find in my parts, and it also doesn't have a power cutoff feature, so I bought a more expensive one that:
1: uses a common battery: 9v
2: has a autopoweroff in case I leave it on for 30 min

This one has a "REL" button (relative) which you use when checking ohms; you hold the leads togther and whatever that reading is, you press the REL button and "REL" shows up on the screen, which means now it's doing the subtraction for you.

A multimeter has to operate over a wide range of variables; they measure kiloohms and megaohms; the lowest ohm scale is sometimes 200 ohms, and on some multimeters 20 ohms.
When you get a regulated mod, it is specifically expecting low ohm ranges less than 10 ohms

 

[edyle]

Yeah, I would still like to have a digital multimeter for other purposes....so I am gonna exchange this one and see if I got a dud. Guess for $6 I can exchange it once or twice to see if I can get a winner in the bunch.

Wondered anyone else out there has had to return a few of these for that reason? I guess I could have tried putting in a fresh battery...but all the other functions were working ok, and it seemed to test the voltage output of the battery fine....it just had too much resistance in the test leads for me to want to use it on testing coils.

Could that have been off because the battery installed in it was low/dying out?

No the total resistance on the leads and connections could well amount to an ohm of resistance; sometimes just twisting the leads where they connect to the meter itself rubs off some corrosion or dust and stabablises the measurement; sometimes the probe solder joint has a problem and fiddling with it causes the reading to fluctuate more.. yes the test leads themselves is where the problems usually lie on a cheap multimeter; sometimes a smart person buys the cheapest multimeter but buys high quality test probes separately.

 

[edyle]

First, I hope this is an OK place for this thread. I have no idea why, but I am unable to post in the New members forum, which is where I originally intended to put this. I seem to be able to post in any other forum but there. So, anyone have ideas on that?


.

Congratulations! It means you're no longer considered as "new". You have Graduated!

 

[Bored2Tears]

Just a thought. A multimeter is a great tool to have around the house and car that will pay for itself many times over. It really pays to have a good one and learn how to use it. The better ones are more accurate and safer. There are tons of tutorials on youtube for testing ecig equipment as well as all things electrical. I have both analog and digital models.

For testing ecig equipment, it is generally not dangerous. As always though, be very careful that you know what you are doing around higher voltages, household electricity, etc. Electricity can kill you. For higher voltages and amps, the thought of using a cheapie multitester scares me to no end.

Yeah...I decided to keep it as the other functions work well enough.

 

[danny4x4]

Exactly what Edyle said.
Touching the probes together and getting varying resistances may be caused by :
1) unsteady hands
2) crappy probes
3) crappy connection

 

[crxess]

Yeah, I would still like to have a digital multimeter for other purposes....so I am gonna exchange this one and see if I got a dud. Guess for $6 I can exchange it once or twice to see if I can get a winner in the bunch.

Wondered anyone else out there has had to return a few of these for that reason? I guess I could have tried putting in a fresh battery...but all the other functions were working ok, and it seemed to test the voltage output of the battery fine....it just had too much resistance in the test leads for me to want to use it on testing coils.

Could that have been off because the battery installed in it was low/dying out?

Get the $6 back and buy an Evod.
When you are serious, Buy an actual multimeter worth something. If you have to go for cheap, consider $20-$25 ON SALE and nothing from Harbor freight - Cen-tech

 

[Bored2Tears]

There was a bit of sarcasm involved with posting a $700 Fluke, there really are cheaper models of the Fluke to choose from.
I posted that tho' just to show that like most everything else you get what you pay for.
I would also point out that there is more involved in making a meter accurate than just the resistance in the leads, and the lower we go with the resistances we use the more inaccurate cheap meters become.

Yes, I picked up the sarcasm. I was just unsure if I conveyed my internal debate accurately . All the responses confirmed my original thought. The $6 multimeter isn't entirely useless to me so I will keep it. It's accurate enough for reading voltage output and other functions reasonably accurately. For the resistance of coils, I will just step up to a regulated mod which has more accuracy than this meter & convenience of just slapping the atty on.

for $20 or $30 I don't need another , more accurate multimeter.... I'll spend that toward a good regulated mod.

once again, great advice here from seasoned vets. I kinda suspected for $6 I was holding out too much hope for using this to test coils.... But it was worth a try and I can use it on other projects.

i wasted WAY more money on liquids that dashed my hopes and dreams.

 

[Bored2Tears]

Thanks to all who have responded. I appreciate the additional insight.

 

[Alien Traveler]

Exactly what Edyle said.
Touching the probes together and getting varying resistances may be caused by :
1) unsteady hands
2) crappy probes
3) crappy connection

When measuring low ohms by touching wires/coils with probes will always give crappy results without alligator clips: small touching area, contaminations, oxides… Specialized ohm tester for vapers works around this problem with help of 510 connector.

 

[edyle]

Yes, I picked up the sarcasm. I was just unsure if I conveyed my internal debate accurately . All the responses confirmed my original thought. The $6 multimeter isn't entirely useless to me so I will keep it. It's accurate enough for reading voltage output and other functions reasonably accurately. For the resistance of coils, I will just step up to a regulated mod which has more accuracy than this meter & convenience of just slapping the atty on.

for $20 or $30 I don't need another , more accurate multimeter.... I'll spend that toward a good regulated mod.

once again, great advice here from seasoned vets. I kinda suspected for $6 I was holding out too much hope for using this to test coils.... But it was worth a try and I can use it on other projects.

i wasted WAY more money on liquids that dashed my hopes and dreams.

Yes the multimeter is a general purpose tool and for $6 it's better than nothing; you can check for shorts on mods; you can measure the voltage under load on a rebuildable; you can check battery voltage while charging; check what your charger voltage output is

 

[Frenchfry1942]

When I started to rebuild, I had had...issues. I had one of those little $7.99 black box thingamajigs. I finally decided to run to Walmart for a multi-meter. The readings matched...so I continued to stress.

 

[Bored2Tears]

Get the $6 back and buy an Evod.
When you are serious, Buy an actual multimeter worth something. If you have to go for cheap, consider $20-$25 ON SALE and nothing from Harbor freight - Cen-tech

Why should I buy an Evod with my $ ? I have one. I was partly going to start rebuilding my Kanger coils to save $.

 

[Bored2Tears]

When I started to rebuild, I had had...issues. I had one of those little $7.99 black box thingamajigs. I finally decided to run to Walmart for a multi-meter. The readings matched...so I continued to stress.

How did it turn out for you?

 

[Frenchfry1942]

How did it turn out for you?

I had those two meters and the ohms meter on my MVP2. Anyway, I was learning to rebuild on a Kayfun 3.1 clone. Kinda small in there with my big fingers. After doing one...or 25 that I thought were okay, I started to move to getting a 1.2 or 1.3. I was just learning, and getting weird numbers had me stumped. But, being able to test the ohms early really helped. I think most of the time I was messing up due to lack of experience. I am glad that I have the two meters, though.

Thanks

 

[dannyrl]

I think I have the same DMM as you, it's red, super cheap, and from Harbor Freight, and I had a 0.7 resistance reading when I touched the probes together.

These multimeters are not going to be super precise, you know that from the price, but that 1.2 ohm reading you got would normally be negligible in typical applications, like probing resistors that are 50 ohms and up. I was provided this DMM for my several electronics course labs, and the lowest resistors we've used were 200ohm. A 1.2 ohm variance from that wouldn't cause any alarm. But in vaping, we build at such low resistances, that this calibration error would actually make a huge difference.

Just take the reading before you probe the coil, then probe the coil, and take the difference. I used this method for a while until I decided to buy a 510 that could precisely read my coil resistances up to two decimal places. I could confirm that even with the 1.2 internal resistance of the DMM, taking the difference gave the same resistance that my 510 ohm meter measured.

Keep the cheap DMM for measuring the voltage of your batteries, checking voltage drop, etc. If vaping is the only thing you use it for, you don't need the features of a more expensive DMM in my opinion.

Also, I kind of just skimmed over this thread, but if you're building low resistance coils, the MVP can be unreliable. I once built a coil that read 0.9 ohms on the MVP, but when I checked it on my 510 ohm meter, it was 0.3ohms.

 

[crxess]

When measuring low ohms by touching wires/coils with probes will always give crappy results without alligator clips: small touching area, contaminations, oxides… Specialized ohm tester for vapers works around this problem with help of 510 connector.

Have you spent any time with a decent meter? Good probe leads and proper care = works right. At least my Sperry does. Reads -0-ohms when shorted as it should.

Why should I buy an Evod with my $ ? I have one. I was partly going to start rebuilding my Kanger coils to save $.

The suggestion was to invest in something what works for the same $$. Hey, it would give you one more backup.

 

[edyle]

Have you spent any time with a decent meter? Good probe leads and proper care = works right. At least my Sperry does. Reads -0-ohms when shorted as it should.


The suggestion was to invest in something what works for the same $$. Hey, it would give you one more backup.

Do you mean it reads 0.00 ? or is it 0.0? I'm guessing it wouldn't read 0.000

 

[Bored2Tears]

The suggestion was to invest in something what works for the same $$. Hey, it would give you one more backup.

I see. More backups are always good. Thanks.

 

[Avid]

First, I hope this is an OK place for this thread. I have no idea why, but I am unable to post in the New members forum, which is where I originally intended to put this. I seem to be able to post in any other forum but there. So, anyone have ideas on that?

That's why-------->NEW MEMBERS INFORMATION: Information for our new members. Reviewing the information here will enhance your ECF experience and can answer many frequently asked questions. Members may reply to stickies that are not locked but may not start new threads.


btw... I don't know anything about multimeters But I have figured out how to break my new ohms meter