What would you guys recommend? If you have a link to one that you have great! I was thinking that the multimeter was most accurate? what do you guys think?
What is the most accurate way to measure resistance on your atomizers?
- Thread starter CLOUDKICKER
- Start date
- th_trl_thread_readers 0
- Status
If you want to be really accurate, you'd need a high end meter. I've heard Fluke makes good DMMs. I just have a cheaper one that works for me.
I'd think any multimeter would work. But some of them bounce around by quite a bit. The one I have, I use for wiring my subwoofers. Two dual coil 4 ohm subs wired down to 1 ohm could read 1.2, .9, etc. So I'd probably want something that's a little more exact on the tenths. I've never built a coil, but I'm sure most people who do build use meters that are pretty accurate. But I'm a newbie, so don't take anything I say as professional help.
It depends on how low you plan to build. If you are going to stay above .2 ohm you can use a multimeter that has a resolution of .1 ohms. If you are building below .2 ohms you will need a multimeter or ohmmeter with a precision of .01 ohms.
Multimeters aren't that good at low ohms, any cheap atty ohm reader would be my first choice, one with 2 decimal places. After that you're looking at 2 or 3 hundred dollars for a bonding meter/low ohms meter (maybe you can get them cheaper these days). The reason why atty ohm readers can be cheap and good is that they are designed for measuring atty resistance, where a multimeter uses very low current so as not to damage a delicate electronic component or circuit, which limits the accuracy at low ohms.
Standard, cheap multimeter form fasttech, for example this one has accuracy (1%+2d). It means that during measurement of 1ohm coil the uncertainty will be ± 0.03 ohm... Theoretically 
safer will be to take 0.1 ohm accuracy. So, if you don't use a coils below, let's say, 0.5 ohm it will be sufficient. Please note that measuring resistance by use of multimeter you always have to subtract wires resistance.
Measurements done by good vv/vw mods (for example SX or PV, etc.) are also OK.
safer will be to take 0.1 ohm accuracy. So, if you don't use a coils below, let's say, 0.5 ohm it will be sufficient. Please note that measuring resistance by use of multimeter you always have to subtract wires resistance.Measurements done by good vv/vw mods (for example SX or PV, etc.) are also OK.
Well lets see.
I have read some of the most off the wall information about ohm meters that isn't even close to accurate on this thread.
Recommending $20 Meters as Dependable/Accurate............... well, lets hope Op isn't going for Super Low ohm builds.
I advise VERY CAREFUL investigation of your choices in equipment.
Op, Read and add to your knowledge base:
Low ohms measurements you can trust
I have read some of the most off the wall information about ohm meters that isn't even close to accurate on this thread.
Recommending $20 Meters as Dependable/Accurate............... well, lets hope Op isn't going for Super Low ohm builds.
I advise VERY CAREFUL investigation of your choices in equipment.
Op, Read and add to your knowledge base:
Low ohms measurements you can trust
Last edited:
Standard, cheap multimeter form FastTech, for example this one has accuracy (1%+2d). It means that during measurement of 1ohm coil the uncertainty will be ± 0.03 ohm... Theoretically
Measurements done by good vv/vw mods (for example SX or PV, etc.) are also OK.
Ezah,
This is a common misconception, so I'd like to clear it up. When a meter is spec'd at 1% accuracy, that is 1% of full scale.
Since the lowest range on many meters is 200 0hms, a 1% accuracy is +/- 2 ohms!
An inexpensive ohm reader designed specifically for attys is a much better bet; these are designed to work in the low-ohm ranges we work with.
Also, when you take the "zero" reading (touching the two probes together) you aren't actually measuring the resistance of the lead wires. What you're measuring is the baseline offset of the meter at very low resistances. Try this experiment:
1. Measure the resistance touching the two probes together. On my meter, I get a reading that bounces between 0.6 and 0.5 ohms.
2. Then, remove the negative lead from it's connection, and touch the positive lead directly to where the negative probe plugs in. Guess what? The reading bounces between 0.6 and 0.5 ohms.
3. Do the same thing in reverse; unplug the positive lead, and touch the negative lead to where the pos lead plugs in. Again, 0.6-0.5 ohms.
I don't mean to say that you shouldn't subtract out the "lead resistance" - all I'm saying is that what you're measuring is not really the resistance of the probes, it's a baseline offset reading that comes from the meter electronics.
I'd also like to follow up on Ian's comment. He is correct that an ohm-reader designed specifically for attys can use higher sensing currents than a generic multimeter. However you don't have to spend hundreds on an accurate galvanic ohm-meter. Youcan get very accurate resistance measurements using a lab power-supply, something like this:
30V 5A 110V Precision Variable DC Power Supply Digital Adjustable Lab w Clip New | eBay
(It helps if you pre-wire a 510 connector to some leads). Set the voltage output to, say 3 volts, read the current that results, and do the math.
</soapbox>
Sorry, but SURELY NO - accuracy usually refers to READING, not full scale.
Sorry. I'm not sure how to convince you of this, but I will try.
If accuracy is specified in terms of the units of measurement, then this applies across the whole scale. A voltmeter specified to +/-20uV will be within +/-20uV across it's entire range. However, when accuracy is specified as a percentage, it is always a percentage of the full-scale range.
There are some very accurate meters for which both are specified - For example, a specification might read "+/-0.1 percent of reading, +/-.01 % of full-scale". In this case, the worst-case accuracy applies. For readings >= 10% of full-scale, the measurement will be accurate to 0.1% of the reading, but at the very bottom of the range they are good only to .01% of the full-scale value.
Your garden-variety multimeter is not such a precision instrument. (Even if it's a $50 one). The accuracy spec for these is always % of full-scale.
I don't know how to convince you of this. I design industrial measurement equipment, (and use very accurate meters for calibration and certification purposes). I'm not just making this up.
I'm wide open for new knowledge, especially from people smarter than me. So could you please comment the National Instrument or Fluke (page no 3 and 4) explanation of multimeter accuracy?
USA High Accuracy Canada Edition Ohm Reader by USA Ohm Meter
$8.09 Atomizer Resistance Tester (Ohm Meter) at FastTech - Worldwide Free Shipping
what do you guys think of these regular ohm meters?
$8.09 Atomizer Resistance Tester (Ohm Meter) at FastTech - Worldwide Free Shipping
what do you guys think of these regular ohm meters?
FastTech tester has one big disadvantage: fixed "plus" pin in 510 connector. So there will be no contact for some attys...
Hi, Ezah,
By the way, I hope you don't see me as argumentative. I really am trying to clarify some things that are often mis-represented here.
From the National link:
1. Accuracy
Accuracy essentially represents the uncertainty of a given measurement because a reading from a digital multimeter (DMM) can differ from the actual input. Accuracy is often expressed as:
(% Reading) + Offset
or
(% Reading) + (% Range)
or
±(ppm of reading + ppm of range)
Also, note that the meters they are referring to are these (link at the bottom of your reference page)
Digital Multimeters (DMMs) and LCR Meters - National Instruments
These are very expensive, very accurate meters. What they didn't mention is that sometimes meters are speced as "1% accuracy or 3 Digits" (Note that "3digits is a measurement of "% full scale!") If you look at the Fluke page, that is the spec format they use.
As I said, expensive calibration-grade meters will be spec'ed with this kind of detail. Your generic multimeter, which quotes just "1% accuracy" is not this grade of meters; the spec, while nominally true, is generally accepted to be with the caveat that this is full-scale, not reading-related.
For example, I have this meter:
http://manuals.harborfreight.com/manuals/37000-37999/37772.pdf
It's a fairly reasonable hobbyist multimeter.
For resistance, in the 200-ohm range, the accuracy spec is:
(@200Ω) 0.8% of rdg ±3D;
If I'm measuring a 199-ohm resistor, the 0.8% part of the spec means that the value will be +/- 1.6 ohms, the 3D error adds another .3 ohms. The resulting accuracy is .95% of the reading.
If I'm measuring a 20-ohm resistor, the .8% gives +/- .16 ohms, the 3D error adds .3 ohms. 2.3% error
If I'm measuring a 2-ohm resistor, the .8% gives +/- .016 ohms, the 3D error adds .3 ohms. 15.8% error
So, as you start getting down to the lower ranges, the 3Digit error starts to dominate severely.
Not to say these are useless; the "Measure the probe resistance" technique cancels out a very large portion of this error, since you're now effectively making a differential measurement (coil vs no-coil, everything else the same) but there's no way these meters can measure a 1-ohm load with anything remotely approaching 1% accuracy!!!
Hope that clarifies things; I might have oversimplified them the first time I responded.
ABSOLUTELY NO. First of all thank you very much for time you spent for explanation.
Actually I'm a little shocked
According to what you say the KEY word in specs is "of reading" - if there is only percentage, without "of rdg" phrase, it means full scale accuracy. So even the quite expensive mmeter like this one Fluke has the accuracy referenced to full scale... Right? It is hard to believe... but I believe you. I'm not convinced in 100%, I will talk about it with other experts in Poland, however I feel you are right...THANK YOU very much again - you opened my eyes for something I didn't know.
And now let me say something more
For others... Believe me - measuring the attys coils IS NOT the rocket science
To prove it I've just made an experiment:1. Let's take the the atty with microcoil ~0.6 ohm:
2. Let's take the cheap multimeter (~30USD) and measure the wire resistance:
3. Then let's measure the atty:
So 1 ohm subtract 0.4ohm for wires gives 0.6ohm...
4. Now let's take the ... TA DAM... the cheapest multimeter from Fasttech and check the wire resistance:
5.And measure the atty:
So again 1 ohm subtract 0.4ohm for wires gives 0.6ohm...
and that's it...
Hi, Ezah,
Yes, you have to read the specs pretty carefully, and make sure you understand what they mean.
However, for the fluke, the specs are better than they might seem. (Always refer to the manual, not the top-level specs!)
From this:
Fluke 179 True RMS Digital Multimeter
The specs for resistance are:
Resistance Accuracy[1] ±(0.9% + 1)
Max. resolution 0.1 Ω
Maximum 50 MΩ
So .1% +/- 1D. They also include the curious footnote:
[1] Accuracies are best accuracies for each function
So who knows what that means.
This is the wrong meter for the application, though. This is a specialized meter for measurement of true RMS values for different waveforms. It's expensive because of that feature, not because of it's general performance. As an ohmmeter, it's a pretty average performer.
ETA: Sorry, I forgot. YES!!!, measuring the DIFFERENCE between 2 different resistances close in value will give you much better results, which is why subtracting the "resistance of the wires" will give you pretty accurate readings. (But, as I said above, you're really NOT subtracting the resistance of the wires!)
Yes, you have to read the specs pretty carefully, and make sure you understand what they mean.
However, for the fluke, the specs are better than they might seem. (Always refer to the manual, not the top-level specs!)
From this:
Fluke 179 True RMS Digital Multimeter
The specs for resistance are:
Resistance Accuracy[1] ±(0.9% + 1)
Max. resolution 0.1 Ω
Maximum 50 MΩ
So .1% +/- 1D. They also include the curious footnote:
[1] Accuracies are best accuracies for each function
So who knows what that means.
This is the wrong meter for the application, though. This is a specialized meter for measurement of true RMS values for different waveforms. It's expensive because of that feature, not because of it's general performance. As an ohmmeter, it's a pretty average performer.
ETA: Sorry, I forgot. YES!!!, measuring the DIFFERENCE between 2 different resistances close in value will give you much better results, which is why subtracting the "resistance of the wires" will give you pretty accurate readings. (But, as I said above, you're really NOT subtracting the resistance of the wires!)
Last edited:
And more importantly you've [edit - Ezah's post and pics] demonstrated the usefulness of backup measuring devices. What would one do if he made a coil and doubted his one and only measuring device?
You've also tempted me to drag out my Fluke187, Fluke123, Fluke77, Fluke12, reliable cheap Digitech QM1535 all versus my Fasttech atty reader, but I've already done the Fluke187 vs Fastech comparison and was happy with the result. But the quality or consistency of the cheap atty readers is the main concern, especially for those using coils under 0.5 ohms, so I would get 2 atty readers if I had no other backup.
Also, what twgbonehead has posted in this thread is 100% on the money, that wonderful info can be taken in or ignored at the reader's pleasure. That power supply he linked would have been my next suggestion
You've also tempted me to drag out my Fluke187, Fluke123, Fluke77, Fluke12, reliable cheap Digitech QM1535 all versus my Fasttech atty reader, but I've already done the Fluke187 vs Fastech comparison and was happy with the result. But the quality or consistency of the cheap atty readers is the main concern, especially for those using coils under 0.5 ohms, so I would get 2 atty readers if I had no other backup.
Also, what twgbonehead has posted in this thread is 100% on the money, that wonderful info can be taken in or ignored at the reader's pleasure. That power supply he linked would have been my next suggestion
Last edited:
- Status
Similar threads
- Locked
