Scullcom Hobby Electronics #31 - Design & Build a Milliohm Meter

[@jimmylightfinger1216]

A well paced lecture on how a project is developed: from the start block diagrams and their relationships, Then a purposed schematic to iron out some obvious kinks and electrical issues, to a breadboard to test the theories calculated prior, make adjustments or changes to anything outside desired specifications, fine tune, final testing, prototype and test, all with jelly bean parts...marvelous. Spot on.😊

[@vernonbosshard9317]

You remind me of my old instructor, Dr Chow, wasn't so good with english but could get the job done, he would draw out three large classroom dry erase boards with circuits then explain them. This was a little tech school in Texas, only got a little AAS degree but I wish I could go back in time and learn more.

[@Mrhvac]

Well, I know I'm late on the comment. I wanted to tell you what a great job you did and how much I appreciate your work. Video like this are so helpful and I learned a lot from yours. I'm just glad that people like you take the time to do them.

[@JetNmyFuture]

Those are some seriously impressive hand drawn schematics! Vastly beyond my capability. Excellent project and a nice explanation of the circuit.

[@scullcomhobbyelectronics1702]

Many thanks.

[@scullcomhobbyelectronics1702]

Chris Tate (commented below) raised the point about using a lower constant current source. During my initial project design I did consider using a INA131 instead of the INA106. The INA131 has a gain of x100 so you could use a 10mA current source instead of a 100mA current source. I did initially test both options but I found the INA106 easier to set up and trim the offset voltage. The wiring would also be slightly different as pin 5 on the INA131 is grounded and the reference pin is also different. The INA131 is also more expensive than the INA106. Another option would be to use a INA110 which has switchable gain options but is in a 16 pin DIL package. In the end I went for the INA106 which was very accurate and stable and worked well and was cheaper.

[@RobEinstein]

Love your channel and projects. That's the difference between (real) electronics and being just a kit assembler. Excellent! Keep up more projects coming!!!

[@scullcomhobbyelectronics1702]

Thank you.

[@velceaiulian6439]

Thank you sir for the patience with which you explained the principle of operation directly on the diagram, and for offering a constructive version accessible to those who really need such a tool. For a long time I somehow wanted to complete my lab with something like this but now I have a template that I will definitely make. Boys, subscribe to the channel as it deserves, not just for the way this gentleman explains, not just for the "toy" ideas you see! Thank you again !

[@marcallima7048]

Amazing projects, by the way! Love this concept-to-product video format!

[@navigator171]

This is the third time I'm watching this video. The interesting thing is that every time I watching I learn some thing different, I will build this project, already have most of the parts here with me. Thanks for share your knowledge Sr.

[@scullcomhobbyelectronics1702]

Many thanks. Glad to hear you find it helpful. Regards, Louis

[@cws-999]

Its an absolutely pleasure to follow your teachings. Terathanks you for all! :-D

[@zikermu]

Thank you for presenting your excellent and detailed project to us. Great professional work.

[@LawrenceKesteloot]

Outstanding, thank you for all the details. These videos must take so much time to make! It's really appreciated.

[@scullcomhobbyelectronics1702]

+Lawrence Kesteloot Thank you for your kind comments.

[@nkp5845]

I love how you explain your designs from the block diagrams to the detail PCB- I will probably never need such a meter but I learnt a lot from how you designed it using the various ICs. I know for a project I will use your MAX680 design.

[@scullcomhobbyelectronics1702]

Glad you enjoyed it. Thanks.

[@antiquephotographyodedlevy]

I love you’re projects thank you for the efforts made into making them and explaining everything .

[@asniexasniex3571]

I really cant thank you enough for your video. I learned so much. Please never stop doing these kinda videos. And if you can find more time please do more frequently. I am pretty sure a lot of people would want that. Also the main disadvantage with starting up electronics is how pricey the test gear is and the people who cant afford them or cant source them in their demographic area have no other go. But with the help of videos like yours and other youtubers a lot of people can build their own. Like someone mentioned above it would be really awesome if u can explain how each component was selected for eg: what to look for( freq response, slew rate and other characteristics) in an opamp for a project. And for the next project please build a really precise voltmeter like the one you have. Not everyone could afford a 6 1/2 multimeter in order to calibrate the circuits u have designed in other videos. It would be really cool if it had a digital autocalibration with a help of a micro :). Once again thanks a lot really appreciate your videos.

[@scullcomhobbyelectronics1702]

+Asniex Asniex Thanks for your comments. You must have read my mind. My next video project will be on designing and making a precision 6½ Millivolt meter with auto calibration option at low cost suitable for the hobbyist. I have been busy of late but hope to complete this video in the next few days.

[@asniexasniex3571]

That really chuckin awesome

[@pierrekiefer21]

a very interesting project Louis and great video as all your other videos and tutorials ! Been following you for years. Thank you very much ! I sincerely do hope that you and your family are doing well. It is nearly 2 years since your last video. Take care Louis. Greetings from Hamburg.

[@leonerduk]

A cute-looking design. I'll be attempting to build this one up, using one of Barbouri's PCBs from oshpark. One thing I note is that the 2ohm upper limit of this unit seems to be entirely due to the panel meter. I found myself a 4 1/2 digit display panel meter on eBay that goes up to 4.3V, so with any luck I'll end up with a meter with a greater range that can go to 4.3ohms instead, but still with the given accuracy and precision of the unit presented here.

[@Scorpio722]

Great presentation for a practical Milliohm meter.

[@scullcomhobbyelectronics1702]

Thanks George.

[@cowshittt]

I dare to say that your content is more educational than Dave's from EEV, too bad we havent seen from you lately.

[@supersilve]

Thank you very much for the tutorial video. Well explained in making this professional instrument. Well done.

[@qzorn4440]

Mr. Scullcom has created a Hobby Electronics Cult with his creative high end projects 😀 there should be a channel just for this type of culture with viewer feedback 🥳 new projects kits.

[@coldfinger459sub0]

Thank you very much for your videos I cannot wait to build from your projects I’m a hobbyist a beginner learning went back to College to take electronics classes. Cannot wait until my grandson gets old enough so I could build some of these projects with him.

[@cranegantry868]

Very nice build. Loved watching this. Very thorough.

[@First2ner]

Two things: 1. If you don't have a good multimeter, you have no way of knowing if your source is really 0.1000xxx mA. 2. 100mA is good for low resistance, but will cause an error because of heating the resistor with 0.1A Thanks for video, as always love to watch them

[@scullcomhobbyelectronics1702]

+First2ner Thanks for your good comments. I have found using a good quality resistor either a 0.1 ohm or 1 ohm at 0.1% tolerance, you can use that to set the reading and that should give you 100 mA, at that tolerance level. I take your point about the 100mA with regards heating but I have found that in practice with resistances below 1 ohm it has little effect and usually you are testing a resistance for just a few seconds (for example a 0.1 ohm resistor at 100mA will only needs to dissipate 1 milli watt of power).

[@mnovo]

+First2ner This is why the resistors are in parallel. 8x 1 watt resistors in parallel is a max rating on 8 watts. 1mW requirement means it's not even an issue. Awesome

[@mightyastro2656]

been wanting something like this for a long time but just needed someone to explain how to do it so simply. Don't have time to make right now, but will defiantly be a project in the near future!Thanks alot

[@scullcomhobbyelectronics1702]

+Mighty Astro Thanks for your comments.

[@RambozoClown]

Very nice project. Always nice to build your own test gear.

[@bobedge3149]

Thank you so much. Very interesting, and remarkably simple. Perfect for measuring the resistance of high current (up to 2700A) welding cables. At those currents they can heat up enough to melt the cable sheath, even with 120mm squared cable. Part of my job is to recommend what size of cable is needed for a given length, and current. Now I will be able to actually quantify the job. As you can imagine a 100 meter length of 120mm cable can cost many hundreds, even thousands of pounds.

[@brianfields6665]

Really helpful video. Thank you very much! I have 2 of these recently brought in for repair, so will follow your excellent suggestions and instruction. Enjoy your very positive approach!

[@steverodgers1112]

Hi Louis, As usual, a very thorough attention to detail. Another KiCad user here. I used to use Cadsoft Eagle, but switched when Eagle 5 would no longer run on the latest Linux distributions. For front panel work, I've had pretty good luck with Librecad printing 1:1 to a laser printer, then using glue sticks to stick the paper down to the front panel (Glue stick idea comes from electronicstrivia). I then use a drill press to drill holes, and a nibbler tool and nibble square and rectangular holes. The only downside to the nibbler is that it is tedious (and sometimes painful) to use.

[@scullcomhobbyelectronics1702]

+Steve Rodgers Thanks for the comments and info.

[@das250250]

Wonderfully built and explained with care and attention to detail .ty .

[@scullcomhobbyelectronics1702]

Thank you. I will be posting an update on this project soon as a PCB is now available for this project.

[@jstro-hobbytech]

Great circuit design. Thank you

[@PapasDino]

Super work Louis, thanks for sharing your design and final build!

[@scullcomhobbyelectronics1702]

+Dino Papas Thanks Dino.

[@franciscofernandes7526]

Good project worth building. Cheers

[@twotone3070]

This was excellent explanation and video production. I just wish I needed a milliohm meter.

[@47smitten]

🎉 he's still alive. Keep up with the channel.🤗

[@bobedge3149]

Thanks so much for this project! I have to test welding machines which can output up to 2700A, so knowing what your load resistance, which is usually just lots of welding cable is vital. This will make my job calibrating so much easier

[@scullcomhobbyelectronics1702]

Glad you found this project useful.

[@esnam6557]

This is a very neat and useful project. Thank you much for sharing.

[@scullcomhobbyelectronics1702]

Thanks for your comment.

[@whoam42a1]

Thanks. A very detailed video

[@fanfan-tz2tk]

Very interesting. Thanks for sharing

[@MarkGarth]

Excellent project and very well explained.

[@scullcomhobbyelectronics1702]

+Mark Garth Thanks Mark.

[@eded8045]

great stuff!! If you visit this project again perhaps a multimeter attached to the rear to show readings above 2 ohm. Its almost an ESR checker?

[@robertcalkjr.8325]

Nice video. That is a handy low Ohms meter.

[@scullcomhobbyelectronics1702]

+Robert Calk Jr. Thanks Robert.

[@ovalwingnut]

You R ""The Resistance Whisperer". Really wonderful project! Sorry I'm so late to the party. It is amazingly clever, well thought out and explained - with amazing detail! I must posses this "high quality test unit" Thanks so much professor. Cheers from So.CA.USA 3rd House On the Left.

[@farschaad]

Very nice explanation. Thank you so much for sharing this video.

[@passioneelettronica]

Hi, very nice project, I will make this, I had the same idea but you make a very professional project !

[@thomass7877]

Amazing ... Easy to understand even for a noob like me ... 👏

[@ToltecMerc]

Perhaps your 4.5 digit meter has a trimmer on the back. You could fine tune the reading to match the voltage reading on the more accurate Keithley meter. I am gathering parts for this project now. I've been wanting one to track down shorts on PCBs. Thanks.

[@scullcomhobbyelectronics1702]

+ToltecMerc Thanks. Yes you are right their is a trimmer inside the panel meter, I will give it a try.

[@patrickpafarnis5798]

Very nice project, thank you very much for showing, and give me the possebility to build by myself.

[@scullcomhobbyelectronics1702]

Thanks. I will be uploading an update on this project soon using a smaller PCB and some improvements to the circuit.

[@chanc.7648]

Very good project.

[@WilliamCulver]

Great project, thanks for sharing.

[@scullcomhobbyelectronics1702]

+William Culver Thanks.

[@berniken6511]

Thank you for the info on the 0-2v panel meter I have now ordered it............................Berni

[@ChrisHalden007]

Excellent. Thanks

[@piotrhoowicz8284]

Great job as always! Very instructive video. Actually it's so simple and usable that I will try to make a full smd version, just for learning purposes. Thanks for sharing...

[@scullcomhobbyelectronics1702]

+Piotr Hołowicz Thanks. A full SMD version should be quite neat.

[@stevec5000]

Those Ebay banana plugs on the red and black leads will tend to be intermittent if the spring around the outside of the center pin is loose like they usually are. I got some like that and found that I had to solder one end of the outer spring to the center pin before they would make good contact.

[@scullcomhobbyelectronics1702]

Thanks Steve for your valid comment. The one I use are quite good quality so they seem to have been OK so far. Regards, Louis

[@monstereat90]

this gentleman is a savior🫡

[@scullcomhobbyelectronics1702]

Thank you

[@milanmladenovic]

Great project ! Thank you.

[@scullcomhobbyelectronics1702]

+Милан Младеновић Thanks.

[@Aviprink]

Really nice project sir 👍 please make more.

[@scullcomhobbyelectronics1702]

Thanks.

[@enginerdy]

You must have the pro edition of DaveCAD... those schematics look amazing!

[@scullcomhobbyelectronics1702]

Thanks :)

[@robertfenney]

This was a great project!

[@scullcomhobbyelectronics1702]

+search4robfen Thanks.

[@heinzschneider9554]

Thank you for the explination, learned a lot

[@scullcomhobbyelectronics1702]

Glad you found it helpful.

[@marcelojordao6602]

bom trabalho!! parabens!!!

[@mnovo]

Question about the INA106... If R1 is 10k and R2 is 100k, should it not be a gain of 11? Gain = 1+(R2/R1) This is where I always fail to understand... Very precise and detailed tutorial. So much clarified. Thank you, I learned a lot! I used this theory to construct a more accurate shunt for my DC load.

[@scullcomhobbyelectronics1702]

+Mike Novo Thanks for the comment. In this circuit I am using the INA106 configured as a Differential Amplifier the gain is therefore x10. We are using both the + and - inputs and therefore the output is Vout=10(Plus Input - Negative Input). If you were to configure the INA106 as a non inverting buffer then the gain would be x11 but in that case the negative input pin (pin 2) would be grounded. Hope this clarifies the point.

[@mnovo]

Of course. I see that now. Thanks!

[@pisze1973]

Thank you.

[@OmarMekkawy]

Thank you for your video.How the 10 Ohm resistor compensate the 100 Ohm resistor effect ?. is there any calculations or any formula or any topic talking about this ?

[@AlexanderBrevig]

I love your videos! Great stuff :)

[@scullcomhobbyelectronics1702]

+Alexander Brevig Thanks Alexander.

[@donmoore7785]

Brilliant!

[@stevegelnett4469]

Well done, sir.

[@BM_brb]

I'm a new subscriber and a fan sir. 😘

[@SteelBlueVision]

I can't seem to understand one thing. What is the point of using 7 0.1% precision resistors(@ 15:57), only to trim them after. If you are going to trim, 1% or 5% resistors would have sufficed, I would imagine. Or, is there something I am not getting here? Thanks for this video, it was very informative!

[@scullcomhobbyelectronics1702]

+SteelBlueVision Thanks for your comments. Yes you could use 1% tolerance resistors. I tried it and it worked just fine. The main reason I used 0.1% was to improve and long term stability over time and due to temperature.

[@leglessinoz]

any reason you couldn't use a panel-mount multiturn pot for the zero trim other than cost?

[@YashKudale]

Great video !! I like the total project done in one video concept it's great for such small project. One request that please include some videos where you design this project, what do you keep in mind while designing that project and also component selection. These are some parts where noobs like me have a hard time. Thanks for the video!! And one more request if you can make a video on op amp stability having tons of problem there.

[@scullcomhobbyelectronics1702]

+Yash Kudale Thanks for your comments. Good point about the design process. Also I have been considering a video on op amps. May be something I can do when I have time.

[@vernonbosshard9317]

I can't believe how much they want for some equipment, is it that much better then say building this? This one appears to be really accurate and sensitive.

[@iceberg789]

nice. may be you want to build a auto ranging volt / current meter next time ?

[@scullcomhobbyelectronics1702]

+iceberg789 Thanks. Interesting !!!!

[@nraynaud]

I'm wondering: why do you use precision resistors when you are also adding a trim capability? Can't you just factor the error in the choice of the potentiometer?

I was about to ask the same question.

[@scullcomhobbyelectronics1702]

+nraynaud1 The reason I used 0.1% tolerance resistors was to reduce thermal drift errors effecting the overall resistance. The 15 turn trim potentiometer will have some drift error over time even after setting it. So the overall effect can be reduced by using good quality low tolerance resistors.

[@nraynaud]

interesting, lower absolute tolerance on value also means higher time drift, then?

[@SteelBlueVision]

+nraynaud1 No, resistors with a lower TCR (nothing to do with tolerance, although very low tolerance resistors tend to have decent TCR characteristics as well) will drift less with temp changes.

[@jmcorp8021]

@@scullcomhobbyelectronics1702 i know super late to the party, but i was just thinking it might be good to use some big pots on the front panel. then put a switch to switch the precision calibration resistor back into circuit. that way you could fully calibrate it each time you wanted without having to open the case.

[@shamvibhute136]

nice work.

[@rayenbenharb7656]

Nice work, but can you give us more detail about the display

[@berniken6511]

Thanks for the great milliohm meter video. Could you tell me the actual company where you bought the 0-2v panel meter, I have searched Ebay upside down without luck. Thanks........................Berni

[@scullcomhobbyelectronics1702]

+berni ken Thanks for your comments. The 0-2v panel meter I purchased on eBay was from the seller "yourcartmax" the direct link to the ebay listing is below: www.ebay.co.uk/itm/261284812938?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[@JohnDoe-u3b]

What panelmeter are you using or can you provide a link to a similar one?

[@fieldsofomagh]

great project and well explained.I was just wondering why the need for a milliohm meter?

[@scullcomhobbyelectronics1702]

+Tom OConnor Thanks. A milliohm meter is very useful for checking the low resistance of components such as wires, switch contacts, relay contacts, coils and PCB track traces. Some times I use the copper track on homemade PCB boards to provide low value resistors for some projects - helpful for making up current sense resistors where you need just a few milliohms in value.

[@g.o.b.s8914]

+Scullcom Hobby Electronics oooh nice, id love to see a video one day on that even if its just on drawing ;)

[@jeppet8479]

First of all, love your videos. Would be awesome if you made an all in one DC precision multimeter with the ohm meter, voltmeter and then add precise amp meter. Basically making a poormans Keithley 2000 multimeter. Could really use one of those :)

[@scullcomhobbyelectronics1702]

Thanks for the comment. Nice idea but I think it may be costly to fully copy a Keithley 2000. Regards, Louis

[@supyrow]

those are nice leads!!! really nice work! I truly enjoyed that, now I have to make one! a great program for laying out panels is "Front Panel Designer" try it out (no connection to the company, just like their free software) Be Well! i love it that you use KiCad too!

[@scullcomhobbyelectronics1702]

+su pyrow Thanks for the tip on "Front Panel Designer".

[@onfireminium3798]

what a great video !

[@jagdishsawant3469]

5digit voltmeter is included in parts list nor any suggestion for equivalent is added.pls suggest the suitable millivoltmeter .

[@davidaz4933]

Nice job Small and simple circuit Only you should note capacitors Of the LM2940 should be ESR of 0.1-1 Preferable tantalum

[@scullcomhobbyelectronics1702]

+David Az Thanks for your comments.

[@MrMonomonster]

Great project!!! Wondering - can you really trust the panel meter?

[@scullcomhobbyelectronics1702]

+MrMonomonster Thanks. The panel meter I used on the project proved to be accurate up to 0.1mV reading. So it was fine what the project set out to do. This panel meters are a little more expensive than some others costing around £8, but worth it.

[@capriracer351]

This is an excellent project. I will probably build it and use my Keithley 197A for the meter since it is the most accurate meter that I own. I see possibilities for using this for finding shorts while troubleshooting PCB's. One question that I have though. Would it be better, at least in my scenario of using this to find PCB faults, to use 10ma as a source instead of 100ma to reduce any heating? Or, do you think that this would not matter?

[@scullcomhobbyelectronics1702]

+capriracer351 Thanks. I have found that using 100mA current source to be the best option as you are able to get a better voltage reading and therefore a higher degree of accuracy. Some commercially available Milliohm meters on the market do use 10mA source current but in practice I have found their results to be poor on very low resistance readings below 20 milliohms. The higher the current used the better the accuracy of the results. Of course there may be some difficulties in providing a high value very accurate constant current, but today with the Linear Technology IC LT3092 this is relatively easy up to a maximum current of 200mA. At these levels heat is not really an issue. So to summaries I would recommend you stick with the 100mA.

[@ElectronPcRepair]

Can this be used as Short circuit detector

[@mohammedshalash7842]

Thanks for the useful tutorial, It would be nice to have a 200mA version as this would be used in PAT testing for IT equipment to measure the earth continuity and resistance for 0.1 ohm Pass and more than that wold be fail, modifying the circuit to 200mA is simply changing the resistors to half the 12.5 ohm to produce the 200mA and the LT3902 is capable of 200mA as per the datasheet, but my problem is the zeroing of the module would I need to change the AN106 side? please advise. Many THANKS

[@scullcomhobbyelectronics1702]

The INA106 provides a fixed x10 gain using its internal laser trimmed resistors. By increasing the current to 200mA you would need to halve this output gain to x5. However, as the INA106 is a precision IC I would leave it as it is and then add a further precision OP Amp on its output which would half the result and give you the correct reading you require. In order to maintain the accuracy and stability I would recommend you use a INA105 configured as a divide by 2. If you checkout my No. 11 video (5 minutes in) I describe how to use a INA105 in this way: kzbin.info/www/bejne/ZmKsc5eemKqghdk Hope this helps. Regards, Louis

[@mohammedshalash7842]

Thanks

[@mohammedshalash7842]

Since my application is a PAT tester circuit for earth continuity I realised I don't need hi accuracy +-10% will be more than adequate for the purpose, so I opted to use V ref with MCP617 opAmp and 1% highly matched 22k resistors as difference amplifier config with a mosfet,and sense resistor of .22ohm to generate stable 200mA require to do the test in the range of 0.05 to 0.5 ohm this way it is quite suitable for the PAT testing required by the current regulations as well as very cheap setup, less than £5.00 total components cost, Many THANKS for your informed tutorials I enjoy them. Kind Regards

[@bgdwiepp]

Great video as usual, just wondering what the current consumption is like? I assume only a handful of ma.

[@DaveCurran]

+bgdwiepp it will be at least 100mA when in operation, plus whatever the meter takes.

[@scullcomhobbyelectronics1702]

+bgdwiepp When a resistance is tested the current consumption is just over 100mA. However, when the unit is switched on and the input leads are left open circuit the current consumption is very low only a few mA mostly due to the current used by the panel meter.

[@FlyingShotsman]

+Dave Curran, no, if the test clips are not shorted together, there's no path for the 100mA to return, so the LT3092 floats to its highest output voltage and consumes only its quiescent current (10uA set pin current plus a few uA for its internal circuitry). You can see this at 43:47 in the video, where the clips are open circuit and the Keithley meter reads 5.8V. The other ICs will draw a few tens of uA, plus a few mA for the panel meter.

[@bgdwiepp]

Scullcom Hobby Electronics Thanks for your reply! thats quite good, i think i might build one up myself

[@scullcomhobbyelectronics1702]

PROBLEMS REPYING TO PIRATEMAN COMMENTS BELOW: So answer here - I used the INA106 OP Amp as it is high precision with an accuracy of 0.025% and a non-linearity error of only 0.001%. The 2 volt panel meter I used was a good quality one with good accuracy and resolution down to 1mV. I found it to be better than using the Arduino ADC.

[@TheStuffMade]

Great project, thanks for sharing. Have you considered some kind of thermal EMF compensation? I guess it is perhaps not essential until you get down into the 10s of microohm.

[@scullcomhobbyelectronics1702]

+TheStuffMade Thanks for your comments. Thermal EMF compensation is really only needed at much lower resistance readings in the low micro ohms and below. Also if you wanted to check such low resistance readings you would also need to screen all the input leads to stop pick up of noise.

[@1959Berre]

Well explained.

[@scullcomhobbyelectronics1702]

Thanks.

[@zari63]

Hi there is chipper method to do this if u have 3 diode in parallel and u want to know which on faulty , use power supply with limit current and put minus probe on one diode and the same time touch the diodes and u feel the shorted diode become warmer then other .simple no??

[@pagepro211]

Amazing!

[@chrispychickin]

I would think that 100mA is a bit excessive for a test current. Isn't there an alternative to the INA106 with higher gain to work around this? Otherwise, a very interesting project, I've used other INA series op amps for precision current measurement before, and they've worked out great, with very little supporting circuitry

[@SirArghPirate]

Great tutorial as always. Have you made a precision voltage meter as well?

[@scullcomhobbyelectronics1702]

+SirArghPirate Thanks. Well a precision voltage meter may be a project for another day!

[@SirArghPirate]

+Scullcom Hobby Electronics Great! Perhaps you can recommend a digtal multimeter with mV precision for hobbyists? I often have to measure lipo-batteries and I don't trust my cheap multimeter.

[@scullcomhobbyelectronics1702]

+SirArghPirate With regards your question about a good digital multimeter for the hobbyist with mV precision, I can recommend the following: Extech EX330 AC/DC Mini Digital Multimeter 4000 counts at about £40 or if you wish to spend a bit more; Extech EX510 Digital Multimeter 6000 Counts CAT IV 600V at about £84 The prices do vary a lot from different suppliers. I have found www.rapidonline.com to be reasonably priced. Be careful on eBay as some prices for these meters are much higher.

[@learnbox3783]

Can we convert this to micro-ohm-meter?

[@seyedmarashi]

WellDone Man, Excellent Thanks

[@scullcomhobbyelectronics1702]

Thanks Seyed.

[@jorgemef]

Hello. Where do you get the 2v 4-1/2 digits panel?

[@wuerike]

It's a amazing project!! It seems to be very accurate, but I have a question, could I use it on industrial application on a motor factory, measuring the inductor resistance of the motors?

[@scullcomhobbyelectronics1702]

Thanks. Yes it could be used to measure low resistance of motor winding if you wish.