Cheap Microohm Meters

[BillW50]

I was tired of my many multimeters only measuring down to only a tenth of an ohm. As I build my own heater coils for my electronic cigarettes (aka vaping). And my Eleaf ohm meter made for this purpose that can read down to 0.01 ohm is off by like 0.17 ohm (it was like 8 bucks, so what do you expect and you can't calibrate it). So I needed something better.

I found some really accurate low ohm meters, but they were hundreds to thousands of dollars. Why so much? If you know the voltage and the current applied, it is super easy to calculate the resistance. And millivolt and milliamp multimeters are dirt cheap. Why nothing cheap for milliohm (or microohm)?

Well I might have found something. It is suppose to read down to 1 microohm (yes, that is 0.000001 ohm). It wasn't thousands, nor hundreds of dollars, but about 50 bucks. Nor was it big and bulky, but tiny. I thought it was worth a shot.

http://www.ebay.com/itm/111378757065

I am not sure of the logic of these low ohm meters, but they have two leads per connection. The idea is that they null out any resistance the leads has (I thought that is what the ohms adjust was for on analog meters?). Anyway I am not sure how that is suppose to work like constant current or voltage or something. This one too has the same thing. Every time you press the button, it zeros out the meter. So that part is good.

I quickly discovered if you are charging the 3.7v 1400mah lithium battery at the same time through the USB port. That you can kiss off any accurate resistance reading, at least on microohms. It would jump around +/- 800 microohms easily. Without USB, I could get at best jumping around 10 microohms. But you have to wedge it pretty tight to get that, otherwise it would jump around +/- 200 microohms easily. The spring clips are pretty weak and while they claim the clips are gold plated, either they are not or so thin it doesn't help much.

I dunno, I was looking for something cheap that can read at least one milliohm accurately. Well I guess this can do this very well. But has anybody found anything better?

[motocoder]

They use a 4-wire, aka "Kelvin" connection. When measuring low ohm values, the voltage drop from the resistance of the test leads can be significant. With a 4 wire ohms measurement, this problem is reduced greatly by  using two of the leads to send a constant current into the device under test, and the other two leads to sense the voltage across the device under test. Because the leads sensing the voltage have very little current flowing through them, the voltage drop due to the resistance of the test leads is negligible. The other two leads, the ones sending the test current, may have significant voltage drop, but this does not impact the measurement at all.

Many desktop meters can do 4-wire measurement. Micro-ohm meters have some additional features to go below what is even possible to measure with a normal meter with a 4-wire ohms capability. I believe mostly this is that they send a much larger current into the device.

Another feature that is sometimes useful is the ability to "null" the measurement. This just takes the current value the meter is reading and stores it away, and then for future readings it subtracts this value. This somewhat compensates for the lead resistance. You can manually do this, even with your existing meter by just subtracting that 0.17  ohm value. See if  you can get access to a 4-wire capable meter, though, to see just how accurate this is and whether that will meet your needs.

[TimFox]

Another feature found on very-low resistance meters is low-frequency AC drive, rather than DC, with four-wire connections to avoid the effect of thermal EMFs between the different metals in the circuit.

[motocoder]

Another feature found on very-low resistance meters is low-frequency AC drive, rather than DC, with four-wire connections to avoid the effect of thermal EMFs between the different metals in the circuit.

Oh, that is quite interesting. Can you explain how that avoids the EMF from the bimetal junction? Is it because it can then sense a different absolute voltage between the two polarities, and using that estimate the voltage from the thermal EMF and subtract that out?

[NoItAint]

Check this out for some idea's on how you can use a Mooshimeter to do some in circuit measurements,  but this is a pretty high ampere circuit.

http://hackaday.com/2014/01/27/measuring-185-%C2%B5%CF%89-in-circuit/

Mooshimeter does two measurements at once.
I don't know if other meters, or two meters can do this unless you plot several measurements.

[motocoder]

Check this out for some idea's on how you can use a Mooshimeter to do some in circuit measurements,  but this is a pretty high ampere circuit.

http://hackaday.com/2014/01/27/measuring-185-%C2%B5%CF%89-in-circuit/

Mooshimeter does two measurements at once.
I don't know if other meters, or two meters can do this unless you plot several measurements.

That  is a pretty cool device. Too bad it doesn't support Windows Phone

[ywara]

Another feature found on very-low resistance meters is low-frequency AC drive, rather than DC, with four-wire connections to avoid the effect of thermal EMFs between the different metals in the circuit.

What HP does in their DMMs - much simpler - is to disable the current source and measure the residual voltage. It's called "offset compensation". The residual voltage should be the sum of any TE potentials and whatever else is in the circuit. It is easy to do manually if you don't have a good four-wire ohmmeter.

Measuring low resistances is pretty trivial provided you have a stable current source and a decent voltmeter. You don't really need a high-quality micro- or milli- ohmmeter.

[robrenz]

The DE-5000 LCR meter will do a great job of measuring to mili Ohm resolution as shown in my short video below. It is 4 wire Kelvin and uses AC excitation which eliminates thermal emf errors which is a must at this level and below.  The standard alligator clip attachment needs the clips replaced with true Kelvin clips to get this level of performance.

[robrenz]

Measuring low resistances is pretty trivial provided you have a stable current source and a decent voltmeter. You don't really need a high-quality micro- or milli- ohmmeter.

It is not that simple if you need any level of precision.

[TheSteve]

We whipped up a bit of a low resistance measuring box the other day at work for fun. It is nothing more then 4 AA batteries feeding an LM317 in constant current mode set to 100 mAh. The current can be set with a single resistor of the proper value. It doesn't get much simpler or cheaper really. Use clip leads to connect to your wire and then measure the voltage across it to determine the required resistance needed. We were using it to measure the resistance of the joints in a clip together slot car track and of copper tape. It is nothing more then a very budget 4 wire setup that should work great for your application.

[edavid]

What is the point of measuring the cold resistance of a heating element?
Wouldn't you be better off measuring it at working temperature?

[motocoder]

The DE-5000 LCR meter will do a great job of measuring to mili Ohm resolution as shown in my short video below. It is 4 wire Kelvin and uses AC excitation which eliminates thermal emf errors which is a must at this level and below.  The standard alligator clip attachment needs the clips replaced with true Kelvin clips to get this level of performance.

That is really cool. However, making those nice Kelvin clips like you did there is impractical for 99.99999% of the people here

[Vgkid]

Another option would be to grab a hp3456a and a set of ebay kelvin clips. It gives you 100microOhm resolution, and statisticsa

[Someone]

Another feature found on very-low resistance meters is low-frequency AC drive, rather than DC, with four-wire connections to avoid the effect of thermal EMFs between the different metals in the circuit.

Oh, that is quite interesting. Can you explain how that avoids the EMF from the bimetal junction? Is it because it can then sense a different absolute voltage between the two polarities, and using that estimate the voltage from the thermal EMF and subtract that out?

Agilent has one of their videos going into some details here https://youtu.be/vydZQRqUm9M

[Vgkid]

For low resistance measurements, the 3456A features an offset compensated Ohms function.

[motocoder]

Another feature found on very-low resistance meters is low-frequency AC drive, rather than DC, with four-wire connections to avoid the effect of thermal EMFs between the different metals in the circuit.

Oh, that is quite interesting. Can you explain how that avoids the EMF from the bimetal junction? Is it because it can then sense a different absolute voltage between the two polarities, and using that estimate the voltage from the thermal EMF and subtract that out?

Agilent has one of their videos going into some details here https://youtu.be/vydZQRqUm9M

Thanks, it was what I theorized in my post; you measure the value with opposite polarity currents, and can remove the EMF contribution by comparing the two values. Probably a better way to say it is that you do a differential measurement.

[Gyro]

Maxim App note AN106

www.wentztech.com/radio/resources/Projects/AN106.pdf

Use your own choice of reference and op-amp. Subtract any meter reading you get before / after to eliminate any thermal emfs. Test current up to 1A, battery powered.

[kripton2035]

here on my web repository you can get schematics of simple devices that can measure the milliohm
http://kripton2035.free.fr/continuity-repos.html

I made the cypress one and it works quite nicely. I'm trying to upgrade it by adding a 100ohm range, and a speaker to ear the low ohms.
http://kripton2035.free.fr/Continuity%20Meters/continuity-an220.html

[robrenz]

The DE-5000 LCR meter will do a great job of measuring to mili Ohm resolution as shown in my short video below. It is 4 wire Kelvin and uses AC excitation which eliminates thermal emf errors which is a must at this level and below.  The standard alligator clip attachment needs the clips replaced with true Kelvin clips to get this level of performance.

That is really cool. However, making those nice Kelvin clips like you did there is impractical for 99.99999% of the people here

Thanks, but any stock Kelvin clip can be used to replace the alligator clips of the standard DE-5000 attachment to achieve the results shown in the video.

[robrenz]

This post of mine shows that accuracy below 1 milli Ohm is not trivial. That chart is plotted in % of Reading error on the left side. My point is that getting micro Ohm resolution with a setup has no bearing on the accuracy you are achieving. Notice how quickly that very expensive meters exceed 100% of reading errors at 10 micro Ohms.  The LOM-510 I used in the video has a maximum error of 13% of reading at 10 micro Ohms as seen on the chart.  Another very interesting thing about that chart is seeing that which meter is more accurate depends greatly on what resistance you are measuring.

[HighVoltage]

This post of mine shows that accuracy below 1 milli Ohm is not trivial.

Great chart, robrenz.
It seems the Agilent 34420A is getting such great results with only 10mA of drive current.
The LOM-510A is using 1A drive current, interestingly, I never measured that.

[robrenz]

This post of mine shows that accuracy below 1 milli Ohm is not trivial.

Great chart, robrenz.
It seems the Agilent 34420A is getting such great results with only 10mA of drive current.
The LOM-510A is using 1A drive current, interestingly, I never measured that.

That is because it is also a nanoVolt meter and has at least 100x voltage resolution to make up for the 100x reduction in drive current.

[BillW50]

Wow! I had no idea how interesting this topic would become. Thanks everybody!

@motocoder: Ah I should have elaborated more about the 0.17 ohm error on the Eleaf meter. One it changes from day to day. I have seen it be off by 0.27 ohm before. Now today I checked it with three different coils (2.1425, 0.1510, and 0.1093 ohm) and it is only off by 0.04 to 0.05 ohm higher. Later on today it will probably be some other error. Maybe the position of the moon and the planets has something to do with it, who knows?

@edavid: Why measure cold resistance of a heating element? Well the most common wire used for this purpose is called Kanthal, which consist of mainly iron, chromium (20–30%) and aluminium (4–7.5%). And what many people do is to build the coils where each loop touches each other. Sounds strange I know, since you would think the coils wraps would short to each other. It does in fact at first. But they have a method they call checking for hot spots. You apply current and the coil should turn red in the center and expand outward. If it does, you are good to go.

If it doesn't, that means one or more wraps are shorting. Easy to fix, you just stroke the coil with a screwdriver or something and recheck for hot spots. What happens is when Kanthal is heated, it forms a protective layer of aluminum oxide (alumina). Aluminium oxide is an electrical insulator but has a relatively high thermal conductivity. Thus even when the wire touches each other, they are electrically insulated. They also claim that Kanthal resistance doesn't change in respect to temperature. I am not sure if that is 100% true, but so far I haven't seen any changes yet.

Another popular wire is nickel wire (Ni200). Now nickel wire does change resistance with heat. In fact, that is why they use it for devices that does temperature control. And how these generally work is by reading the resistance at room temperature, this is your baseline and gets stored. Now as it heats up the resistance changes (I believe it increases in resistance). I never saw a huge change personally. Say a cold nickel coil reads 0.10 ohm. When heated to 400°F it might be at 0.11 ohms. Apparently these temperature control devices can read far more accurately than their resistance display shows. As mine for example can be set between 200°F to 600°F in 10°F steps. And during my experiments it does a pretty good job of it. As it is generally within 20°F of the setting.

Now they say you are not ever suppose to use nickel wire without temperature control. As over 600°F it gets really soft and it could cause shorts, etc. Nor does nickel oxide either, so the coils shouldn't touch each other (unlike Kanthal). Then there are some health concerns about inhaling hot nickel wire too. Although it is generally believed that 600°F and cooler should be fine.

[edavid]

Thanks, that clears up a lot.  I was also wondering why people make their own heater coils... do you burn through (ha ha) a lot of them?

[TheBloke]

Ooh I somehow missed this thread, and it's very much up my street.  And I see now it was started by a vaper, awesome

Vaping is my current hobby and passion - @BillW50, look for me on ECF if you want to discuss a lot more about accurate Temp Control and the technical stuff  that goes with it, such as accurate ohms reading, adjusting for Static Resistance in the atomizer/510s, and adjusting TCRs to vape with different wires.  My main thread on the subject at ECF is here: TC beyond Ni200: Nickel Purity, Dicodes; Ti, SS, Resistherm NiFe30; Coefficient of Resistance

Anyway, back to the topic at hand - to answer your original question Bill, I have already bought two of the very device you are asking about (and for the same reason - vaping!)  :



(Click on any of the images in this post to see them larger)

I also bought two high quality current sense resistors so I could validate their accuracy, and the accuracy of other ohm readers I have or might get.  As you can see, on the left I have a 0.01 ohm resistor with +/- 0.25% tolerance, and on the right it's 0.1 ohm with +/- 0.1%.  (I bought these resistors from eBay - they're used, having been taken out of a military-spec current meter.)

And according to these readings, these micro ohm readers are accurate at least for these resistance ranges - both are reading within the tolerances of the resistors.  I have some 0.001 ohm 1% resistors on order from eBay so I can do further verification at the milli-ohm level; would like to get some 0.001 ohm 0.5% or 0.1% as well if I can find some that are affordable.

I don't believe that they're actually accurate to micro ohm or that close to it.  For certain they're not accurate to six decimals, because the last digit always fluctuates.   The fifth digit was fairly stable for these readings, but does sometimes move about a bit.

I'm generally happy to regard them as definitely accurate to milli-ohm, and at most accurate to 0.1 milli-ohm; 4 digits, 1-in-10,000.  That's certainly good enough for me.

I checked out the current they put out, as my (beginner's) reading on micro-ohm/milli-ohm readers (in particular this document from Megger about low-ohm reading) suggested that the current used by the reader was very important for the accuracy?

In that sense, it's good news/bad news for these micro ohm readers:

 

0.101 A or 84mA - but I'm not sure why I get different readings depending on whether I'm in A or mA mode on the DMM?  Surely 0.101A should show 101 mA or 85mA should show 0.085A?  Not quite sure what's going on there?

Anyway, I believe this is pretty good news because it's way more than the average DMM ohm reader sends - which is usually about 1 or 2mA I believe?  But it's bad news because it's nowhere near the multiple-amps that a true micro ohm reader sends.  (Though in this case, it made me realise that probably, for my vaping purposes, I would never want a true micro-ohm reader - I can't send 10A of current through the wires I would be testing!)

Finally, here's a look inside:

They use a 3.7V Lipo battery, hard wired to the board.   I have been thinking about replacing this with a battery socket.  It's great that it uses 3.7V as I could use any standard 18650 battery, of which I have loads (again, for vaping.)   For some reason, I got very different battery capacities in my two models!



The PCB is quite simple.  I'd be very grateful for anyone's comments on how this is designed and how it does the calculations?  I would really like to make my own reader, and that's one reason I bought the second of these - so I could have one to play about with and maybe change components.



The chip in the middle is the ADS1232 24-bit ADC.  To the left of that, the smaller chip is the STM32F030F4P6 - a 32bit 16kb microcontroller, which presumably does the calculations.   

I'd really like to build one of my own, doing the calcs on an Arduino.  It'd be a fun project. 

Though I just saw in this thread that someone has linked to a plan for a micro-ohm reader, so I'll be studying that first!

Anyway, in conclusion I think these devices are pretty great considering I paid £35 per device ($50) on eBay.   I am very confident that they are definitely accurate at least to three digit / milli-ohm, and quite possibly even to 4 digits.  This is more than good enough for my purposes, and it's very awesome not having to worry about the contact resistance / resistance in the cabling.

My next plans are to:
1. On one, put on better quality cables with stronger clips, so it's easier to grab onto wires/resistors to test.  This is easy to do as they come with a 4-wire screw terminal block.
2. On the other, mod the case to put in a vaping 510 connection, so I can directly screw down an atomizer onto the reader and get a super accurate reading for it; in other words, a home-made 4-wire micro-ohm version of the ELeaf type reader!   I'm hoping this will work out OK as a 4-wire reader if I simply solder two wires onto the positive and two on the negative?  I might need to get them in appropriate positions and/or alignments - that Megger guide I linked earlier has some discussion of that.  Worst case, I'll simply re-create the clips, with permanent clips onto the positive/negative rather than soldering the wires directly.


PS. Bill, throw that ELeaf reader in the bin.  It is known to be not worth the plastic it's made out of.  I made the mistake of buying one too.  Utterly useless if you want a figure close to accurate.  Inside is a hot glue mess with crappy wiring, and it doesn't even have a proper 510 connector.

I started out using my DMM as a reader, because it can do two decimal places.  So before I got the YZKStudio devices, I was measuring atomizer resistance like this:

 

That's a Fat Daddy Vapes v3 Shorty 510, connected to two 4mm banana plugs to plug into the DMM.  Worked well!  That's the sort of socket I plan to put on one of the YZXStudio readers, which will then become my standard vaping ohms reader once I've done it.

[HighVoltage]

To be honest, I had no idea that e-cigarettes is such a market. I feel like I have been living under a carpet, if it comes to this subject.

[dr.diesel]

To be honest, I had no idea that e-cigarettes is such a market.

I had to Google the word vaper, didn't have a clue.

[HighVoltage]

To be honest, I had no idea that e-cigarettes is such a market.

I had to Google the word vaper, didn't have a clue.

Makes me feel better, that I am not alone on this.
My bad excuse is that I never smoked in my life.

[TimFox]

Another feature found on very-low resistance meters is low-frequency AC drive, rather than DC, with four-wire connections to avoid the effect of thermal EMFs between the different metals in the circuit.

Oh, that is quite interesting. Can you explain how that avoids the EMF from the bimetal junction? Is it because it can then sense a different absolute voltage between the two polarities, and using that estimate the voltage from the thermal EMF and subtract that out?

See this link for the manual of an older Keithley unit that uses the AC technique.
The minimum full-scale value is 1.0 milliohm.
The four-terminal connection is done with two AC cables on XLR connectors.
AC excitation also allows phase-sensitive detection to reduce the measurement bandwidth.
http://electronicsandbooks.com/eab1/manual/Hardware/K/Keithley%20www.keithley.com/Product/503%20Milliohmmeter/Models%20503,%20503C%20Milliohmmeters%20Instruction%20Manual%20Rev.%20A%2020040929%20%5B36%5D.pdf

[ywara]

This post of mine shows that accuracy below 1 milli Ohm is not trivial.

You're certainly correct that getting a high-precision (let's say 3-4+ digits) measurement at low resistances requires some doing. However, the 2-3 digits needed in most common applications (contact resistance, heating elements, wire & cable, etc.)  can be easily obtained with a stable current source, range-appropriate drive current, and a normal voltmeter. Probably my "trivial" statement was not nearly specific enough.

I am familiar with contact resistance measurements (0.5-10 mOhm, required accuracy of ~0.1 mOhm) and we have no trouble getting repeatable, accurate measurements with an old power supply and a cheap 3.5 digit voltmeter by using a 1A drive current. There is effectively no heating to worry about - solid metal parts of even small size are not too concerned with 10 mW of heat when there are two big 16 ga. copper heatsinks hanging off them. If we're really desperate we reverse the polarity of the current source and average out the TE voltages.

They also claim that Kanthal resistance doesn't change in respect to temperature. I am not sure if that is 100% true, but so far I haven't seen any changes yet.

It's more accurate to say that Kanthal does not change much. See http://kanthal.com/en/products/material-datasheets/wire/resistance-heating-wire-and-resistance-wire/kanthal-a-1/. 5% across the range. Kanthal A is slightly worse (6%). I assume the rest of the family is similar.

I am not sure what is the temperature used in a vaporizer, but your cold resistance is probably within 2.5% of the resistance under power.

[TheBloke]

It's more accurate to say that Kanthal does not change much. See http://kanthal.com/en/products/material-datasheets/wire/resistance-heating-wire-and-resistance-wire/kanthal-a-1/. 5% across the range. Kanthal A is slightly worse (6%). I assume the rest of the family is similar.

I am not sure what is the temperature used in a vaporizer, but your cold resistance is probably within 2.5% of the resistance under power.

For vaping purposes, Kanthal barely changes resistance at all - a few mOhm at most.

When we do temperature controlled vaping (resistance-based temperature measurement using high-TCR wires such as Ni200 and Titanium), the maximum allowed temperature will be 300°C and the usual desired temperature range is 200 - 250°C.

With Kanthal in non-temp-controlled situations the temperature may occasionally go higher than that, but generally speaking no vaper ever wants to heat his/her coil above 300°C as a maximum.

The Kanthal A1 datasheet doesn't shown any resistance change until 500°C.  A standard resistance for a Kanthal coil is between 0.4 and 1.5 ohms.  Taking 1 ohm as an average, at 500°C Kanthal A1 will increase by 10 mOhm (1.00 -> 1.01).  The TCR seems to be increasing as the temperature does, so I'm guessing the rate of increase from 20-300°C is less than the rate of increase from 300-500°C. 

So I'd think definitely less than 5mOhm by 300°C, probably no more than 2 or 3 mOhm for a 1.0 ohm cold coil.

All that said, accurate resistance reading is pretty unimportant for non-Temp-Controlled/Kanthal vaping.  Most non-TC vaporisers read resistance with an accuracy no better than 100 mOhm, whereas the best TC devices read accurately to the mOhm level (or at least, claim to! - though my testing suggests they generally are pretty good at this.  Only two-wire measurements, but using multiple amps of current.  They certainly are accurate in terms of the achieved coil temperature, something I've tested quite carefully using thermocouples.)

[nctnico]

The DE-5000 LCR meter will do a great job of measuring to mili Ohm resolution as shown in my short video below. It is 4 wire Kelvin and uses AC excitation which eliminates thermal emf errors which is a must at this level and below.  The standard alligator clip attachment needs the clips replaced with true Kelvin clips to get this level of performance.

That is really cool. However, making those nice Kelvin clips like you did there is impractical for 99.99999% of the people here

Thanks, but any stock Kelvin clip can be used to replace the alligator clips of the standard DE-5000 attachment to achieve the results shown in the video.

Can you point to a Kelvin clip in particular? I'm having some trouble to use a HP4274A in the milli-ohm range.

[TheBloke]

The DE-5000 LCR meter will do a great job of measuring to mili Ohm resolution as shown in my short video below. It is 4 wire Kelvin and uses AC excitation which eliminates thermal emf errors which is a must at this level and below.  The standard alligator clip attachment needs the clips replaced with true Kelvin clips to get this level of performance.

Damn, and they're only £60 on eBay.  Now I feel a compelling urge to get that as well, not least just to see exactly how accurate these Chinese YZXStudio devices are   Actually I could have bought one DE-5000 for the price I paid for two of these 'micro' ohm YZXStudio devices..

Like nctnico asked, would be great if you could point to a 'standard Kelvin clip'.  How much does the quality of such a clip matter?

These are the clips that the YZXStudio device came with - four lengths of 20AWG silicone wire soldered to (seemingly) gold-plated plates on a clip.   I'm guessing these cost approximately 1/500th the price of a 'real' Kelvin clip. 



But how much does that matter for milli-ohm accuracy?

[TheBloke]

However,  that said, I think I just got re-excited about these YZXStudio devices.  Now I think I understand the oscilloscope trace I earlier got off my YZXStudio 'micro' ohm reader which I could not understand at the time.

Now that @robrenz mentions:  AC excitation which eliminates thermal EMF errors..

Would this be an example of that?  This is what I get when I put the YZX device on my new Rigol scope



And, because I have owned a scope for no more than 48 hours and am still a complete newbie at all this, could you please confirm that this would be a valid way to probe it?  I clipped the ground lead to the battery negative terminal on the board, and then clipped the Kelvin clips together so that it's measuring its own resistance, and then attached the probe to that:




Assuming this does confirm the YZXStudio device is using the AC method Rob described, then I would think (hope) that makes it a rather good device for £35 / $50?   At least as a milli-ohm reader, if not more?

Is there any chance it might be accurate to 4 digits?  It certainly appears to be so when I check my reference resistors, but I can't be completely sure.  As I mentioned in my earlier (too long) post, it sends somewhere between 85mA and 101mA of current, if that helps to judge its accuracy.

[TheBloke]

One more scope output on the YZXStudio reader. 


The first screenshot was when I had the two Kelvin clips connected together.  This time I used two probes, one per Kelvin clip.


This shows the same 50hz AC signal on each probe, but they are offset and varying. 






Both show a Vpp varying between 1.5 to 2.5V.  Probe 1 has a VMax in the region of -500mv and a VMin in the region of -2.5V, and probe 2 has a VMax in the region of 2.5-3V and a VMin between 0V and 0.5V.  The Vpp/VMax/VMins are varying a fair bit as the AC signals jump around the scale, but the the frequency and amplitude and Vrms are consistent.





I have no idea if this is meaningful information in understanding what the ohm reader is doing, so apologies if it's not   I'm still very much at the stage where I'm looking for any excuse to measure/test things with my scope

[motocoder]

The DE-5000 LCR meter will do a great job of measuring to mili Ohm resolution as shown in my short video below. It is 4 wire Kelvin and uses AC excitation which eliminates thermal emf errors which is a must at this level and below.  The standard alligator clip attachment needs the clips replaced with true Kelvin clips to get this level of performance.

That is really cool. However, making those nice Kelvin clips like you did there is impractical for 99.99999% of the people here

Thanks, but any stock Kelvin clip can be used to replace the alligator clips of the standard DE-5000 attachment to achieve the results shown in the video.

Yes, after I posted that I finished watching your videos. I saw towards the tail end of video #1 where you had the attachment apart. Looks like it would be straightforward to attach different clips to the TL-21 attachment, which can be found on eBay for $15.

[motocoder]

To be honest, I had no idea that e-cigarettes is such a market.

I had to Google the word vaper, didn't have a clue.

Makes me feel better, that I am not alone on this.
My bad excuse is that I never smoked in my life.

Same here. I was thrown off by someone saying that vaping was their "hobby". I used to like to drink beer, but I would never call that a hobby

[TheBloke]

Quote from: motocoder on Today at 05:31:10

Same here. I was thrown off by someone saying that vaping was their "hobby". I used to like to drink beer, but I would never call that a hobby

But you've heard of people who brew beer and have that as a hobby, right?   Similar concept to vaping as a hobby

I never would have considered smoking a hobby - it was just something I did.  But with vaping it's very different.  There's a huge amount of hardware to experiment with - and/or try to design/build oneself - different techniques to use, liquids to try, and so on.  The experimentation with all of that, and discussion of it with like minded individuals, is what constitutes the hobby.


In my case, it's vaping that has been directly responsible for getting me into learning about EE.  Experimenting with and testing the vaping devices, in particular with regards to temperature controlled vaping - hence the interest in accurate ohmmeters, and also now an oscilloscope - and discussing that with other vapers.

[BillW50]

@TheBloke: Ah another vaper here. That is great news. Now someone will know what I am talking about.    Say with your YZXstudio meter, I don't think that 50Hz is coming from your meter, but from your AC house wiring that your scope is picking up. As I am not seeing anything like that here. What I see is 3.32VDC with the leads open and when you add resistance to be measured, the DC voltage drops.

How it looks like it works to me is two leads supplies a constant current of 100ma. And the other two leads reads the voltage. And figuring out the resistance is easy, you just multiply the voltage times ten to give you the ohms. Hell I got a variable power supply right here that I can do that with. Just tried it on a 2.15 ohm coil and yes it works. It looks like my constant current could use some calibration. As I had to dial it down to 94ma before it came up with the correct resistance.

Ah why does it show 0.110 amp vs. 83.73ma? That is pretty normal. As my UT33B inserts a 0.20 ohm resister in amp mode and a 2.0 ohm in ma mode. Thus why the difference in current. Say I just noticed my UT81B is dead in amp mode, ma works. I bought it slightly used and the guy won it and has no need for a meter. Maybe the fuse is loose or missing or something.

Yes it would be a good idea to add a 510 connector to our YZXstudio. Yes just wire it up just like the clips are wired. And yes, once that lithium battery dies, I'll be replacing it with a 18650 battery too. Say did you know that the Tesla car is powered by 18650 batteries?

http://www.wakeandvape.com/blog/18650-vape-faqs/

Yes those Eleaf meters are totally crap for sure. Today it is reading 0.07 ohm higher. The other day it was only 0.04 higher. And some days it is 0.27 ohms higher. Well it can read volts pretty well. Just wire some test leads or battery holder and just use it for a battery checker.

Wow your main thread on ECF looks excellent. Great job!

[motocoder]

Quote from: motocoder on Today at 05:31:10

Same here. I was thrown off by someone saying that vaping was their "hobby". I used to like to drink beer, but I would never call that a hobby

But you've heard of people who brew beer and have that as a hobby, right?   Similar concept to vaping as a hobby

I never would have considered smoking a hobby - it was just something I did.  But with vaping it's very different.  There's a huge amount of hardware to experiment with - and/or try to design/build oneself - different techniques to use, liquids to try, and so on.  The experimentation with all of that, and discussion of it with like minded individuals, is what constitutes the hobby.


In my case, it's vaping that has been directly responsible for getting me into learning about EE.  Experimenting with and testing the vaping devices, in particular with regards to temperature controlled vaping - hence the interest in accurate ohmmeters, and also now an oscilloscope - and discussing that with other vapers.

Yes, in fact I used to brew beer myself until one day I dropped a large glass carbuoy on my foot, shoving a shard of glass through it and turning my wife's kitchen floor into a mixture of Wort and blood. That was the end of that hobby, mostly because of a desire to keep my wife around

I have to admit I am totally ignorant of all things vaping. I had no idea it was something like cooking or brewing beer or making wine. I will have to look into this further. I think it's great that you're learning about EE, and I support that 100%.

[BillW50]

Say I just noticed my UT81B is dead in amp mode, ma works. I bought it slightly used and the guy won it and has no need for a meter. Maybe the fuse is loose or missing or something.

Pop the back off and yes the 10 amp fuse is blown. Well one mystery solved.   

[TheBloke]

Yes, in fact I used to brew beer myself until one day I dropped a large glass carbuoy on my foot, shoving a shard of glass through it and turning my wife's kitchen floor into a mixture of Wort and blood. That was the end of that hobby, mostly because of a desire to keep my wife around

Oh dear

I have to admit I am totally ignorant of all things vaping. I had no idea it was something like cooking or brewing beer or making wine. I will have to look into this further. I think it's great that you're learning about EE, and I support that 100%.

Well, isn't that vaping is just like brewing beer.  I just meant, that is a good comparison - you said "I drink beer but it's not a hobby", so I used an example as to how beer could be a hobby.

Vaping for most people is a replacement for smoking.  A much healthier way to ingest nicotine and handle an addiction to inhaling smoke/vapour    I am sure for most vapers, the vast majority, that is all it is.  But for some of us it becomes a hobby - the ECF forum, by far the biggest vaping forum, has over 15 billion posts in 8 years from 250 thousand members.

There are loads of aspects that can turn into a hobby.  Actually there is one that is a lot like brewing beer/making wine: mixing one's own e-liquids.  You can buy different concentrated flavours, and then mix them together in different proportions along with nicotine and a couple of other ingredients, to try to get the nicest flavours when you vape.

For me that's not a big thing, mostly because I suck at cooking/working out flavours!   For me, the main hobby aspect is the hardware/technology.  Experimenting with and testing different vaping devices.  Different vaping wires, especially for temp-controlled vaping.  Trying different coils that vape differently.  All that sort of stuff.

[TheBloke]

@TheBloke: Ah another vaper here. That is great news. Now someone will know what I am talking about.    Say with your YZXstudio meter, I don't think that 50Hz is coming from your meter, but from your AC house wiring that your scope is picking up. As I am not seeing anything like that here. What I see is 3.32VDC with the leads open and when you add resistance to be measured, the DC voltage drops.

How it looks like it works to me is two leads supplies a constant current of 100ma. And the other two leads reads the voltage. And figuring out the resistance is easy, you just multiply the voltage times ten to give you the ohms. Hell I got a variable power supply right here that I can do that with. Just tried it on a 2.15 ohm coil and yes it works. It looks like my constant current could use some calibration. As I had to dial it down to 94ma before it came up with the correct resistance.

Ah why does it show 0.110 amp vs. 83.73ma? That is pretty normal. As my UT33B inserts a 0.20 ohm resister in amp mode and a 2.0 ohm in ma mode. Thus why the difference in current. Say I just noticed my UT81B is dead in amp mode, ma works. I bought it slightly used and the guy won it and has no need for a meter. Maybe the fuse is loose or missing or something.

Yes it would be a good idea to add a 510 connector to our YZXstudio. Yes just wire it up just like the clips are wired. And yes, once that lithium battery dies, I'll be replacing it with a 18650 battery too. Say did you know that the Tesla car is powered by 18650 batteries?

http://www.wakeandvape.com/blog/18650-vape-faqs/

Yes those Eleaf meters are totally crap for sure. Today it is reading 0.07 ohm higher. The other day it was only 0.04 higher. And some days it is 0.27 ohms higher. Well it can read volts pretty well. Just wire some test leads or battery holder and just use it for a battery checker.

Wow your main thread on ECF looks excellent. Great job!

Oh OK so you already have the YZX?  I thought you were asking whether you should get one.  That's great then.

Re the scope trace, yeah you're right   I think I must have got the grounding wrong, I wasn't properly attached to the battery negative wire.  I've just done it again and I see what you see, 3.32V without a resistance to measure, then it drops.

This begs a new question:  how is my house AC leaking into an improperly grounded scope trace??  Is that normal?  I did have the negative lead on the probe connected to the YZX, just I guess it wasn't making good contact with the negative battery terminal.  So the AC is coming through the floor, up into the desk, and through the casing of the device?  Do I have some bad wiring in my room/house or is this to be expected?

Anyway that's a shame that the YZX is not using the AC excitation method.  Maybe I will get that 5000 LCR meter as well!  If only to compare accuracy.

Thanks for the re-assurance on the DMM different on A/mA!   

[BillW50]

@TheBloke: Nothing to worry about your AC house wiring leaking throughout the house. You can touch the scope probe too and probably get a better and stronger signal. I often use this as a test signal. I just fired up my LeCroy scope and I just got 1.6v of AC. That is pretty normal. But here in the states most of our outlets are wired for 120VAC. Yours are wired for 220VAC or is it 240VAC, right? Some homes in the states has a few outlets 220/240, but equipment that requires 220/240 are usually hardwired in like central air or something.

Yes I have one of those YZXstudio meters. I have got it down to >3 micro-ohms by shorting the leads. But those clips are the worst cheap clips I have ever used. And it looks like to me when you turn it on, you should short the clips out and press the button quickly. This zeros the meter out. When you press and hold to power down, it also does a zero out (not good when you are measuring resistance). I am still puzzled if it saves the calibration or not when you power off. Sometimes it seems to and sometimes it doesn't.

I don't think checking coil resistance will benefit from using the AC excitation method. Although if I am wrong I am sure someone will correct me.