2-Wire vs. 4-Wire Resistance Measurement (Kelvin) + Wave Winners!
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- Опубліковано 5 вер 2024
- Is a 4-wire resistance measurement worth the trouble? Find out!
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Today's tip is all about how 4-wire resistance measurements work, as well as how a power supply remote sense capability uses the same principles.
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4 wire Kelvin resistance measurement overview:
When can you use a two wire measurement, and when should you switch to a 4-wire measurement? If you don’t know you’re in luck, because that’s what we’re covering today!
measurement. Measuring resistance is often straightforward - you just grab your leads and go crazy.
There are times when a standard 2-wire measurement just won’t do the job, so you have to switch over to a 4-wire measurement. The two main cases I’ve seen people do this, and we’ll get hands-on with each of these in a moment.
The first is using a DMM to measure small resistances. The second is supplying dynamic currents with a power supply. Let’s start with the resistance measurement of a DMM.
A DMM makes resistance measurements by supplying a known current out to the device, and then measuring the DC voltage drop across the outputs. We can actually see this if we measure the device’s output during a resistance measurement.
So, let’s actually make a measurement. Here’s a quick measurement of a 1 ohm resistor - let’s store that value away for later. You might think this looks good, but there’s a problem. The DMM’s test leads are in series with the device. The resistance of the leads causes a small voltage drop, tricking the DMM into thinking there’s a higher resistance. For larger resistance measurements this isn’t a problem, but when you’re measuring small resistances this effect can be significant. Fixture resistance is also a problem in automated testing environments where you have long cables, multiple chained connections, and a multiplexer or relays between the device and the DMM. So, what we can do instead is move the voltage measurement from inside the DMM to the point of test with a second pair of leads.
Now we have four leads, hence a 4-wire measurement. These two leads source current, and these two leads make the actual measurement. Because the voltage measurement has a large internal resistance, the current through this path is nearly 0, and the impact of the lead resistance is negligible.
When measuring that same 1 ohm resistor with a 4 wire measurement, we see the new measured value. If we pull out our 2-wire measurement, we see that there’s a 6.5% difference! Clearly, a 4-wire measurement was the superior choice in this scenario.
An easy way to decide if you should use a 4-wire vs. a 2-wire measurement is to measure the resistance of your measurement lead system and compare it to the range of measurements you’re making on your device. Do the math, look at your error budget and decide if it fits within your acceptable tolerances.
The second place I see 4-wire measurements used a lot is for power supplies. Most pro-level power supplies have a capability known as “remote sense” to control the output. In a power supply, you typically set an output voltage, and the supply tries to provide that voltage regardless of the load. As the load changes, the power consumption changes. So, the supply has to sense the voltage at it’s output and adjust for dynamic loads. The problem they run into is the same - as the current changes, the loss in the supply leads changes based on Ohm’s law, and the actual power delivered to the device changes. So, you can run sense leads out to your actual device under test and the supply will adjust its output based on the voltage of the device, not the voltage at the output of the box.
#DigitalMultimeter #DMM #DMMMeasurement #DMMResistance #MeasureResistance #HowToMeasureResistance #4WireMeasurement #KelvinMeasurement #ResistanceMeasurement #DMMResistanceMeasurement #electronics #electricalengineering #computerengineering
I have done 4 wire measurements before, just that I was measuring a DC motor's coil resistance of around 10mOHM, or PCB power line resistance. So I had to run like 10A or 50A through the resistance and measure the voltage across it with a DMM! I suppose a high precision 4-wire DMM would be less catastrophic??
Hello sir fan from india😄😄
Yeah, the 4-wire option is probably the way to go 😅
Hope it was on camera! I have long been a sub and enjoy your arcs and sparks :P
@@wayneparris3439 😂
@@StigDesign LOL
This event is always exciting!
Still enjoying the fruits of my previous big WIN of the MSOX6000 6Ghz scope - It is in daily use (at full bandwidth) and I have since filled out the bench with another DSOX1204G for the higher risk DUTs.
Next up - 7.5 digit DMM and the USB based VNA! Moving up in the world.
How to win dso. I registered. Wat i need to do further
Welcome to day 2! How do you use 4-Wire measurements?
Sign up now for the sweepstakes and get access to the resource libraries:
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I'm doing 4W resistance measurements since 1989 already, when I purchased my 1st hp3458A @ university. Offset Compensation was the other feature which came with this instrument, to further reduce e.m.f. errors.
Great, that the 34465A/470A also feature both methods.
since i just using my basic measuring tool, i just use 2-wire measurement so far unfortunately. you guys not only giving great products, but also useful knowledge of course
I could die for that Keysight ruler
Well i switched to 4 wires measurments during my classess called "Semiconductor devices" led by my great proffessor Sylwester Nowocien. He teached us about small resistances and why they matter so much. That led us to the question on how accurately meassure the small resistances? Well he was like "Now look what we've gotten from our great Campus dotations" and there were those beautiful Truevolt Series 6.5 Digit Multimeters. After lectures with our precious proffessor our entire year switched immediatelly to the Truevolt series provided by the Keysight. Thank you very much Keysight! Hopefully i could get one to avoid long travles to campus to measure the stuff :D. Too expensive to buy from my student's fee :
hi'''i am a retired JPL/NASA scientist ,Pasadena'''''ive used 2 wire my whole life'''''im going to start using the 4 wire test''''of course it wont help with capacitance''''which is my main measurement type'''''thank you'''''''James.... Manhattan project..1944, los Alamos
Studying Electrical Eng... Hope to win any giveaway so I can use them for my project..
Good luck!
Me too, good luck!
A little off topic, I love the FROGGER screen saver! ON topic, thanks for clearing up this topic. What is the effect of the resistance of the sense leads in a 4 wire measurement?
Ahh.. screensaver?! Is that it? I thought it was MAME running on something, but the way the palette keeps changing, you're probably right...
The sense lead resistance is only important when your measured voltage is very very tiny, like when measuring the resistance of a short, thick piece of copper.
Awesome description on the 4-wire stuff. I've always had troubles getting my head around 4-pin current sense resistors, and your description of DMMs is the first that's really let me get my head around it.
Glad it was helpful!
These precise equipments are gold in this industry.
That smooth jazz during the soldering, lmao!
We're always gettin radd & fuggin bustn
@@KeysightLabs haha, touche !
Well, I've always wanted an oscilloscope since I've been interested in electronics. Right now i'm trying to repair a motherboard and attending many other projects, getting one of these instruments would be amazing for me. Let's hope for the best and congratulations to whoever wins!
Every day we learn new things, just came to know about this. Thanks for great info!
4 wire is the best way to measure accurately. Especially for sensors! It's easy to put together different modules from Keysight via GPIB and automate everything.
Well, I am attempting to measure ESR on Electrolytic capacitors in one faculty project. Also with constant current is easy to determine the capacitance...
Yep! We actually did a video on measuring the time constant with an oscilloscope here:
ua-cam.com/video/o-wegFuA3RA/v-deo.html
8 more days to go. I'm still hoping!!! :)
with you :)
I haven't switched to 4 wire measurement yet, but after this video, I will! :D
Another option available with some meters for resistance is to use the relative measurement setting. You short the leads together and set that as your zero point then take your resistance measurement.
Hey, Daniel, I have to ask -- what's up with the *retro* electronics corner? 👍from me. Anyway, congrats to the winners. Fingers crossed for day 3.
It's been fun to branch out into that a little bit! Picked some of it up for an Ixia/IT project I worked on and just couldn't bring myself to sell it!
@@KeysightLabs Ah yes, I know that feeling.
I am designing a low cost lithium chemistry cell internal resistance classifier and 4 wire is essential.
OOOH WHERE CAN I GET THAT RULER 0:48
about the only time I use 4 wires is when measuring across a shunt
and grats to all the winners!
Oh I really like that E36103A power supply. Clean looks
Beautiful ruler !!
But most important: Congratulations to the winners !!!! Best regards from German Electronics Channel Afug-Info
Love the electroBoom clip 😅
Surprised he haven't managed to blow up a scope yet, must be pretty tough 👍
Would love to win some day, to upgrade my 30 usd jytec dso Ebay oscilloscope.
Always fascinate by all the cool and usefull stuff we can do with it
I would like u to explain 1 over r1 +.1over re+.1over r3
Is that an Atari 800XL in the background? 😍 Congratulations winners!
Yep! It's been fun to play around with
Wow! congrats to the winner 👏
That was the correct way of going crazy with measurments. And Rossman would like to have a talk with you about your ball... those solder joints look a biiiit suspicious.
Yeah, not my finest soldering...
another instance is LCR measurements. Almost all good LCR meters only work with 4 wire or Kelvin type leads
Is there some kind of promotion for students
What's the significance of the 'Frogger' running on the monitor in the back?
Sometimes you're the frog, sometimes you're the car...
All of my stuff is 2 wire measurement. BTW: Love the ElectroBoom clip, just wouldn't let him near my test bench... have you seen his channel!? LOL -- Just kidding, good stuff :-)
Congratulations winners!!!!!!!
If you don't have a 4w measurement device, short the leads together and null that measurement out. This puts your plane of reference for your measurement at the END of the probes, and not at the front of your DMM
You could Add timer on landing page when can I do another roll - due to different time zones
-7 UTC, but that's a good idea!
Very informative, thank you
I'm trying to self teach electronics, so apologies if I'm way off with this comment. But isn't this 4 wire just the same as 'nulling' your test leads. I only have a handheld DMM, so for low resistance meaurements I short the leads, press the Rel button to give me a 0 Ohm reading and then take my measurements. Or have I missed the point?
Useful information. Thanks and keep this useful series going.
What about when using RTD like a PT100 is that a good place for a 4 wire measurement?
Thanks!!
I had been trying to understand this for a while.
I don't deal with 4 wire measurements usually, because I don't work with really low resistance values. But I did use to work with a Keysight 3104 oscilloscope before switching work. Now I've had to buy my own scope, which is an entry level rigol. Talk about downgrading, am I right?
F
I am curious about the DMM you used. Does it have a REF button or something like it so that when you clip the test leads together you can zero them out? Then do the measurement of the resistor.
Nothing against 4 wire measurements but.... "Use the flux, Luke!" =)
With this method i fixed DMMs in the late 80s. Had to dig a little bit in my memory :-)
I just hope I win some keysight oscilloscope.
It's always fun if nearly all your predecessors used 3.5 digit handheld DMMs to track the resistance change of PCB tracks during mechanical testing, this led to hundreds of pages with "interesting" results and obscure effects which they then tried to model. So six years later you come a long with a 7.5 digit bench DMM and do a proper 4-wire measurement and suddenly notice that the effects they spent the last six years trying to model don't actually exist, because they were measuring temperature differences and contact resistance. The funny bit was that the mechanical deformation from the testing made it far more difficult to place probes, so the contact resistance always increased in these experiments.
But it does lead me to a rather interesting question, has anyone ever managed to get a better than 0.1 mOhm resolution on a flex PCB resistance measurement? I highly suspect the moisture content of the PCB was ruining the measurements, because just to get it down to 0.1 mOhm already required baking the boards overnight and taking the boards and DMM into a cleanroom. Now that I come to think of it, the pliability of the adhesive used to attach the copper probably didn't help either I suppose. Bit sad I was never able to get it down to the noise floor of the DMM.
Can you suggest a short locater (tono metre)
You could also cover 3 wire measurements
Whoa lets not get out of hand
hope I will get that oscilloscope..
Can you someday show how to do power/current measurements on a pulse width controlled load like a motor? That seems quiet complicated to me and I would love to know more about that! :-)
measure voltage above a shunt to determine current over time, then find a way to integrate that voltage over time. An OpAmp integrator would work well if you're intending to build it into a product, or just use the Math functions of your oscilloscope.
Please consider giving away rulers like the one you are using :).
hi ! am i the only one having problems registering ? the lanfing page says 'register to unlock content' (hiding the button to enter the daily draw). when i register nothing really happens and i never receive a confirmation email even though i selected that checkbox. i tried different browsers on Windows an MacOS and also checked my spam folder ... no result :-( ... that makes me a bit sad as i really would like to take part in this great event.
Sorry to hear you're having trouble! I see that your entry is confirmed in our system, which means you have confirmed from an email. I've also resent your confirmation email to see if you can see it again. However, your entry is definitely eligible and in the draw.
@@KeysightLabs yes, i now received the confirmation 🙂 thank's a lot for checking my registration 👍
Just exactly how modern battery chargers do. Can you go deeper to make it worth it?
Just started with RF and EMC measurements. Would love to win something!
Would like to be able to have any piece of your equipment to help me learn more on understanding and fixing electronics .
wow i hadnt heard of this before
Maybe someday I will become the owner of a Keysight Technologies oscilloscope or multimeter.
I've used 4 wire systems for measuring the conductivity of thin films on glass, and the contraption I used didn't look as nice as the unit you showed nor was it as user friendly.
Nice work! You folks are single-handedly rekindling engineering interest to the masses.
Miliohms measurements
I want power supply n dso. With these two we can do ny thing
2 polish winners it seems, yet it still wasn't me :C Oscilloscopes are so ultra expensive in Poland, it's equal to a typical monthly payout. I could always get a soviet one for cheap, but they mostly don't work and aren't that useful in electronics of our age
Poland showed up strong today, that's for sure!
Congrats to the winners!
**drool**
hi everybody,
how one may participate in equipment drawings?
I measured a (1ohm+-5%) heated resistor, I heat it up to 100 degrees (Celsius) in 100 are 0,9662Ω in 60: 0,9675Ω in 30: 0,9698Ω and in 22: 0,1710Ω my multimeter it cant measure so low values!!
can i has oscope?
Sir Pumpington of Dumpenshire can has oscope
I know, you need oxygen free test leads! LOL What's with Frogger in the background? Is that how you spend your time at Keysight?
I can neither confirm nor deny that I play Frogger at work.
As a hobbiest, why can I not enter?
You can, just put "self" or "none" in those fields
Interesting indeed
I have electronics but no power supplier or tester, would love to win a lab set up.
Plus 1 for electroboom cameo
Espero poder ganar la próxima :)
GIVE ME DA MEETA.
Oh wait, wrong electronics channel.
Nothing I do ever gets anywhere near requiring this level of test gear. Hard to rationalise the outlay.
Why not just use thicker wire ?
Great
Jestem zwykłym człowiekiem. Widzę polak wygrał, daję like c: Congratz m8ts ^-^
I won.....a wealth of knowledge.
And doesn't it feel good!?
How is 4 wire better than just having the meter subtract the resistance of the leads? I though all modern meters could do this.
You can often zero out the lead resistance, but if your load does funky things your measurements can lose accuracy.
@@KeysightLabsI see that, but I was thinking only of static out-of circuit measurements.
What hapend ?
How could I miss it ?
My notifications broke!😕
Hi Daniel can we have a contest over this sexy PCB ruler that can be seen at 1:15 min? :-)
I may have to figure out a ruler giveaway :)
@@KeysightLabs Great, I can't wait.
I prefer the 5 wire measurement system. It's superior.
That's nothing, I'm turning the wires up to 11.
@plemli please, we're over 9000 over here
ooh that is one sexy power supply
I´ll win...
I am hoping to win one of these oscilloscopes so that I can progress in my project for long distance wireless power transmission. BTW I am only 14 yrs old so please beg me an oscilloscope.
really for that demonstration you go with a surface mount resistor? what kind of sickness is happened to you. every normal person would just go with standard axial leaded resistors
Haha, that was the only resistor in the 0-3 ohm range that I had on hand! I'm rarely described as a "normal person" 😅
@@KeysightLabs i could edit that to sane person but that wouldnt make any difference i guess
5:24 to skip to the list of winners on screen
Oh shit, it's a Bogdanoff. I'm going to need the QRD.
I have never made a 4 wire measurement because I don`t have the test gear to do it. hint hint ;)
4 wire measurement is not for a hobbyist or repair shop.
Bruh
This is getting sadder by the day
If by sadder, you mean lit, then yes.
@@KeysightLabs I agree, this 4 wire measuring is lit fam 😅