# Measuring Resistances Between Multiple Wires

Hello,

I am new to using Arduino and I am not quite sure of the extent of its capabilities.

Background information:

I need to measure the resistance between wires. There are 4 wires, and they’re all attached to a single thing on one end. I need to measure the resistance between wires 1 and 2, 2 and 3, 3 and 4, 4 and 1. I have attached a picture of what the wires look like.

The problem:

I need to be able to do this automatically, that is, one circuit has to be able to measure all 4 of these resistances without having to change anything manually.

My question:

Is this something that is possible to do using Arduino? I don’t really care if the solution is complicated, first I need to know if its even possible at all. Please help me if you have any brilliant solutions

Thank you for your time!

The 1st question is, can you measure 1 resistor? And/or can you make all 4 measurements by switching the wires around? Measuring resistance isn't an easy thing with the Arduino...

I believe a digital multimeter works by putting-out a constant/known current (maybe 1mA or less depending on the resistance range) then the voltage is measured and resistance can be calculated.

The Arduino measures voltage] relative to its ground so with no common reference for your measurements you'll have to make/break connections to connect one circuit at a time.

You can use relays or solid state switches to switch the connections. And if there's anything else connected, especially power, you'll have to switch-out those connections too.

It's possible, but we need more information.
What is the resistance range you are measuring?
How accurate does the measurement need to be?
What will you do with the information?

What ranges of resistance are you interested in?

Paul

If they are wires of the same length and gauge there would be no need to measure 4 to 1.
Continuity of 4 is already established with 3 to 4.
Like others have said, more information required.
Is there some particular reason for using Arduino as there are already measuring devices capable of very accurate reading already out there.
4 wire low ohm meter is just one.

The reason for using Arduino is that I need written data of the resistances to be saved, many, many times. The resistances between the wires are around 50 ohms. It doesn't need to be too accurate. Even if it isn't super accurate, I want to know if there is even a connection or a tool that can make it possible to measure the 4 resistance values (and save the values on my computer using Arduino) without manual changes to the circuit.

I can measure two connections at a time right now (measuring 1-2, and 3-4), but I am stumped as to how I could measure 2-3 and 4-1 while I'm already measuring 1-2, and 3-4.

I can measure two connections at a time right now (measuring 1-2, and 3-4), but I am stumped as to how I could measure 2-3 and 4-1 while I'm already measuring 1-2, and 3-4.

You can't measure at exactly the same time but you can quickly and automatically switch connections with relays or analog switches. Relays are more "foolproof" because you can reliably & confidently get a completely open, and a "solid" near-zero Ohm connection.

Just curious - what’s the application here? Why do you need to measure resistances of 4 wires over and over again and it doesn’t need to be very accurate?

steve20016:
Just curious - what’s the application here? Why do you need to measure resistances of 4 wires over and over again and it doesn’t need to be very accurate?

I agree.
A more detailed explanation of what and why would possibly offer a better solution.
A mistake commonly made by "newbies" is to offer a range of solutions rather than the application.

bluejets:
A mistake commonly made by “newbies” is to offer a range of solutions rather than the application.

Described succinctly as the “XY Problem”.

I think I remember a similar request in the past. Might be worth a forum search.

Hi,
OPs diagram;

What is the device?

Thanks.. Tom...

It should be straightforward to measure resistance between any pair of wires.

Use a reasonably sized resistor (so max current is <20 mA at 5V to protect the Arduino pins; maybe you need less current to protect your mystery device), connect one end to an Arduino pin, the other end to a wire and another Arduino pin.

Now you can switch on/off the resistor & wire pair at will. On: pin set to OUTPUT, choice of HIGH (5V) or LOW (GND); off: pin set to INPUT.

Can you attach a bit of circuit between the wires and Arduino pins? Because add a resistor to ground and the wire resistance makes a voltage divider, analog read can give you wire to Arduino measure. One at a time you can measure all 4 in less than a millisecond using one custom cable.

If the resistances are in the order of kilohms, you can even use INPUT_PULLUP as the reference if you do not need great accuracy.