Hello forum, i was currently doing a research on how to measure AC current using current shunts(SMD or Through hole). Its unfortunate that most of the designs i come a cross are for dc current `measurements. Kindly recommennd me any resources that would help me learn on how i can design one (AC current measurement using current shunts with microcontrollers). Your guidance will be of great help.
Thank you.
What voltage/current/frequency. Does it need isolation (mains power).
ACS712 hall-type sensors can be used for low voltage AC.
*Note that ACS712 sensors,and especially the boards they are mounted on
are not safe for mains power.
Leo..
No, is it by design! Using a shunt for AC measurements means both ends of the shunt are powered by the AC power and will prove very dangerous for anyone one or thing connecting to the opposite side of the AC circuit.
That is why current transformers and other indirect measuring methods are used.
Because shunts are so extremely dangerous when used to measure household or industrial AC currents, most people these days use current transformers (CT).
See this guide How to Build an Arduino Energy Monitor - Measuring Mains Current Only — OpenEnergyMonitor 0.0.1 documentation
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Thanks Wawa for the reply, my target is to measure mains current up to 5A on 240V 50/60Hz system. This also requires me to revise means of isolation too
Thanks jremington, I was looking forward to try new techniques without using current transformers. And my current question was, how do Digital multimeters do it (i.e. measuring AC current using shunts safely ). An example is Fluke multimeter and i was looking for any reference or guidance on how they made their design please.
Thanks Paul, true its dangerous but cant it be possible to apply isolation means which may be recommended for shunt designs.
You really need to use a current transformer or better still a current transducer with a 0-5 v output .
You need the isolation for safety and also to protect the Arduino.
multimeters are fully enclosed in a plastic case , so it doesn’t matter about live parts inside - no practical for a home built job .
Consumer measuring devices are manufactured and certified to meet safety specifications required by law. The shunt is enclosed and electrically isolated to prevent consumer access. The assumption has to be made that you will never touch live wires with your bare fingers while attaching test leads.
Shunts that you buy and experiment with are necessarily open and exposed, so that uninformed people (your children, perhaps) can easily touch live terminals and electrocute themselves.
Why bother with a shunt, when CTs are safe and easy to use?
Why not? If you use the Arduino for collecting data and reporting them by some safe channel it is OK. Depending on the application you may for example send the data wirelessly or show them on a display. Or make some sound, control the load (or some other load) by a relay or triac...
@jremington ,what i belived was current shunts are good when it comes to accuracy as compared to some of the hall effect or CT sensors and i wanted to really give it a try by experimenting with shunts as i compare measurement results. However for the sake of safety, the small hardware i want to comeup with will be in an enclosure and i belive it will be a rare case to tamper with it.
Since the AC current and voltage drop to ZERO 100 or 120 times per second, at what point in the cycle are measuring the "current"?
Not safe because you are developing the system - you will need to work with an Arduino that is sitting at mains voltage ; how will you debug it , upload to it ? all possible but difficult and very prone to accident . easily overcome with a current transformer which will also make the solution simplier
Of course you won't develop it connected to the mains. You develop it in a safe environment by simulating mains by i.e. 12 VAC power source with the shunt resistor scaled accordingly.
Use 220 V /220 V, 500 VA isolation transformer for Prject development. One terminal of the secondary coil of the xformer must be solidly connected with the common ground of PC and Arduino. Place the shunt at the ground side. After project development, everything including the Arduino UNO can be put on the 220 V live platform. 5V supply is to be created from 220 V mains.
You may use the isolation transformer but I don't see how is this so much safer: you still work with dangerous voltage somewhere in the circuit. I think you can do 99% of the development with safe simulated signals in project like this.
Toroid CTs (current transformers) are a much better solution. They are 100%
isolated and the voltage is measured across a burden resistor. The fact that
ac goes below 0V means that to measure it with an arduino you have to shift
the CT output voltage positive by enough to get it above 0. There are several
ways to do this . This is one of them.
We know that and basically all of us who reply say so but
... whatever and why the OP wishes to do it the hard way. 
That is the essential nature of this topic. 
ac measurement with current shunt resistor
In order to do this you need to obtain a current shunt rated for your application