How to make a simple Arduino ohmmeter || Arduino tutorial

In this episode I'm building a very simple, but quite accurate Arduino ohmmeter. This project requires only few components: an Arduino, a breadboard, 3 jumper wires and a few resistors. It is based on a voltage divider.
Project page - you can download the Arduino code here:
ElectronFun.com/project_4.php
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Video, edit, voice by Chris Lorkowski
Music composed and performed by Bensound - The Lounge
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[@artemyevtushenko8722]

So clutch! I got an Arduino and a bunch of crappy resistors, that aren't marked well, so this video really saved my ass! Thanks!

[@MasterTreekc72]

This is a very simple but friendly circuit, thank you for share this video!

[@xtreme443]

Is it possible to add a voltage divider to make the input voltage less than 5V but still accurately measure resistance? If so, would you just initialize Vin as whatever the new voltage is?

[@carls.6746]

how would i measure the internal resistance if in place of the unknown resister i use 2 wires with alligator clips or a 510 connector.

[@petrjones9428]

is there a way to measure more resistors at a time? like multi channel ohmmetr and see more values. i want to see values on a lot of potential meters in real time.

[@rvnt5561]

hello, how do i use this same concept but use an external voltage source 24V dc instead?

[@PabloOlivare]

Which oscilloscope do you recommend for $ 150 on ebay or amazon?

[@qzorn4440]

nice and simple for laptop input logging. 🥳 thanks. 🙂

[@ziggymondus8753]

I have just watched a video by Electronoobs on the same subject. Now I have a problem. Their video presents R2 as the reference resistor and R1 as the test resistor. I am guessing that it does not matter which you choose, so long as the chosen 'constant' reference resistor stays constant and you always swap the resistor that is in 'other position'? But that is me guessing. Is my guess right, or is there only ONE way to set the reference/test configuration? [I will ask them the same Q).]

[@batvanio]

Wow, my measurements are pretty accurate. The error was between 1 and 3 ohms somewhere. I added the schematic to my program to display numbers on the microwave screen. I used a 1000 ohm resistor which is actually 1180 ohms. I took measurements with resistances from 100 to 2000 ohms. I guess the bigger the difference between the two resistances, the bigger the inaccuracy.

[@capoman1]

Hey awesome thank you. IN ADDITION, this same rig is can measure voltage and current. So I believe this one connection would allow for measuring all three circuit values.

[@ElectronFunCom]

+capoman1 Thanks for your comment :)

[@allersvp]

DO YOU THINKN IT CAN WORK AS MILLIOHM meter like 200- 900 milli ohms?

[@H2ON_MEA]

Thank you Thank you Thank you Thank you very much

[@yudirudiat6499]

Can it be used for measure earth resistance?

[@tubagames]

me salvou! tks a lot

[@inashamzic6278]

How much can this measure? And how can I measure other values of resistance

[@joelevi9823]

great thanks.. i will just add that i think that the REF resistor should not be too low or high current will get to the ARDUINO and damage it

[@Husseinahk]

This is awesome.

[@ElectronFunCom]

Thank you :)

[@whereverimayroam74]

How do you add more reference resistors?

[@MoMo-cs1ly]

How can I show the results using LCD

[@zelra891]

hey dude. is it possible to use arduino as a voltage meter? it just occurred to me if use an analog input of something.

[@ElectronFunCom]

Zelra 仙賢戀軒 Hi, sure it's possible. I found a nice tutorial about it here: blog.udemy.com/arduino-voltmeter/

[@jimm.4864]

Nice, simple project; however, I have noticed - at least when I use it - the further the difference in ohms between the two resisters, the less accurate it becomes, so it is very important to have a reference resistor close in value to the one you want to measure.

[@stopthelawsuits]

Bit late, but he does cover that at 2:15 in the video. Presumably you could easily just add on more resistor references using the pin outs.

[@zelra891]

This is awesome. In fact, we can make a rather complicated ohmmeter in this way. it's obvious that the accuracy goes really bad when the two resisters are quite 'different'. so we can have more reference resister in the same diagram which we can choose which to use via different output pins. btw, I never tried and wonder if the 5V output in arduino is really 5V, maybe with 5%-10% accuracy or something?

[@ElectronFunCom]

Zelra 仙賢戀軒 Thanks :) You are right - actually I thought about making another video, where I would show a more advanced ohmmeter with selectable ranges (like in an ordinary multimeter).I've just checked the Arduino voltage accuracy. If I can trust my cheap UNI-T multimeter it shows 5.02V, which gives you 0.4% accuracy. It's better than one might expect.

[@dr.mithilfaldesai3561]

Sir, Very simple to understand, thank you. Can I have a program to measure a real time resistance, input voltage, time stamp. How I can export to CSV file. I am using Arduino Nano

[@hugorobitaille6317]

Hi, I have a fluid level sensor that return a resistance value (0-100) and work on 12v circuit in my boat. How can I connect my fluid resistor to your setup ? Thank you.

[@GabrielCox]

Hi, I see this is 2 years ago. Did you ever figure this out? I suspect your tank sensor might be going to gound (only), not 12V. Therefore, I would expect that you could connect arduino ground to this common ground, and then run 5V to your sensor. If it's an existing install (in Europe?, in US it's commonly 240-33) It probably goes to a gauge now which takes 12V and measures the resistance between 12V and ground. But if you unhook this sensor wire from the gauge and put into this circuit using 5V it may work. The only thing I'm not sure about is the inaccuracy factor when getting away from the reference resistor range. I have a boat and I'm interested in doing lots of similar sensor readings as you describe -- then put it on nmea2000.

[@lyesgherbi5862]

Hello Thanks for the Video , I have a question about the measured resistance : What is the limit of the measured resistance , can we measure a resistance a 1000 meter length of cable with resistance of 7Ohms? Regards

[@ElectronFunCom]

+Lyes gherbi Hi, thanks for your comment. I don't know of any resistance limit for this ohmmeter. The thing is - the larger the difference between your reference resistor and the resistor or wire you want to measure, the more inaccurate reading you're going to get. If you need a reasonably precise measurement, you should check the rough resistance of your resistor/wire and then swap your reference resistor to one that has a close value and measure the resistance once more. Your reading is going to be much more precise this way.

[@krishna8905]

can u please tell me gernalised measurment system for this project

[@ElectronFunCom]

What exactly would you like to know?

[@bobthucker2456]

I built this and I am getting inaccurate readings. Across a 15k reference resistor, I am measuring the resistance of another 15k resistor and I am getting 22.35k.

[@Shobinlr]

nice .. i am interested to test this...

[@ElectronFunCom]

Shobin L.R. Thanks! Go ahead and do that :)

[@Elbuencanaldeyutuv]

I need to measure 2 termo resistors at a time, I will see if this video helps me 😉

[@winybandamee9896]

great

[@ElectronFunCom]

Thank you :)

[@paparoysworkshop]

That was neat. Can a similar circuit (with code) be made to check the value of capacitors?

[@ElectronFunCom]

Thanks a lot! To answer your question - yes, such a circuit with code is available on the Arduino's website: www.arduino.cc/en/Tutorial/CapacitanceMeter. As far as I remember, it works pretty well.

[@paparoysworkshop]

ElectronFun.com Thank you.

[@ElectronFunCom]

No problem.

[@pangeachoppers]

I have a question do you know how I could set this up so that if there is a change in the resistance it will trigger an alarm?

[@sdj7122]

How precise will be Arduino if I use this methond. I need to measure resistance 1.3 - 90.7 Ohm. And I would love to use 100 Ohm for the known resistor (tested resistor). I need it to be very precise How much accuracy should I expect ? And can I put readings after that in a variable, so I can use that variable in formula (devide, multiply, etc...) and get new values and print them as integer number ? Also how slow will be Arduino ? I have 4 formulas and 4 variables.

[@ElectronFunCom]

John Doe A lot depends on your reference resistor's precision. I would use a resistor close to 50ohms for your application with 1% tolerance or better. Yes, you can put your readings to variables and use them for further calculations. I'm not sure about the speed, but it shouldn't be a problem.

[@sdj7122]

Thanks for reply. One more question. I plan use 9v battery for Arduino. How much Watts should reference resistor be in my case ?

[@ElectronFunCom]

John Doe There are no high currents, so any wattage resistor will do.

[@paragsangtani3544]

i didn't work softwear give me error

[@julitiwari7234]

eta video?

[@hilmidwiputranto6944]

but I want to make arduino ohm meter because I don't have a multimeter :(

[@ElectronFunCom]

Build one yourself, just use several resistors to get different ohm ranges.

[@andrecutair6650]

Why you need two resistors? Can't you just take the 5V in minus the output voltage, after the unknown resistor, do Ohm's law math, and get the resistance? Why do you need a known value in the equation?

[@batvanio]

It measures the difference between these two connections, not the resistance itself. For example: You have two tubes, one of which has a capacity 3 times larger than the other. There is no way to know how many liters one is if you do not know how many liters the other is.

[@ElectronFunCom]

Can Arduino measure resistance? See here: kzbin.info/www/bejne/mp3dY2egqdx-qLM

[@ronen124]

you used quite an engrossing formula at your sketch: R = Rref * (1 / ((Vin / Vout) - 1)); (-:

[@ElectronFunCom]

It's not as complicated as it may seem. On websites like: www.circuitbasics.com/arduino-ohm-meter you would usually find the following code: buffer= (Vin/Vout) -1; R2= R1 * buffer; My formula does exactly the same calculation, but I don't use the "buffer" variable. Thanks to brackets I'm setting up the proper order of calculations. What is more - my formula is a single line of code.

[@joaoneto4528]

so, to make a multimeter, I need a multimeter.

[@julitiwari7234]

balll