current shunt alternative

[jaderosita2001]

We are doing a research about energy metering and in order to measure the current the circuit we acquired uses a current shunt. It looks like a U shaped metal that is made of manganese. We know that a shunt is just a component that allows current to pass through so it is just a kind of resistor. Is it possible to just use a normal resistor that can handle the power? We are using it at the beginning of the circuit and 220Vac will pass through it.

 

[Sceadwian]

If the circuit you have uses a shunt why are you trying to find an alternative? Shunts are simple effective and cheap. A 50mv full scale reading at 50amps has a resistance of .001 ohms, not exactly a common resistor value. You can use higher values of resistance but it wastes huge amounts of power, limits the current to the device and acts as a voltage divider as well pretty much making them useless for measuring the power of a device because it'll affect the load too much.

 

[dougy83]

Is it possible to just use a normal resistor that can handle the power?

Yes. You can also use a length of wire, a PCB trace, etc. You may have to take the temperature coefficient of the conductor/resistor into account as it will change the resistance should the temperature change due to change in ambient temperature or the conductor self-heating.

 

[jaderosita2001]

We are trying to find an alternative because we can't find any current shunts available in the electronics store near us.

 

[BrownOut]

Yes. You can also use a length of wire, a PCB trace, etc. You may have to take the temperature coefficient of the conductor/resistor into account as it will change the resistance should the temperature change due to change in ambient temperature or the conductor self-heating.

Also, nickel-chromium wire works well.

 

[MikeMl]

We are doing a research about energy metering and in order to measure the current the circuit we acquired uses a current shunt. It looks like a U shaped metal that is made of manganese. We know that a shunt is just a component that allows current to pass through so it is just a kind of resistor. Is it possible to just use a normal resistor that can handle the power? We are using it at the beginning of the circuit and 220Vac will pass through it.

Commercial shunts are designed to minimize variation of resistance vs temperature (primarily due to self heating). Here is a calculator which will help you evaluate how much temperature will effect a homebrew shunt made of various metals. I have made experimental shunts out of Copper, but they are not as precise as commercial shunts...

 

[MrAl]

Hi,


I've made current shunts out of brass. Brass is pretty decent i guess because it has about 4 or 5 times the resistance of copper and
has about 1/4 the temperature coefficient. It's also available in various thicknesses and widths at most hobby shops and some
hardware stores too.
The idea is to calculate the length going by standard width and thicknesses available, and calculate temperature rise with the intended
current level, then purchase the right thickness and width. Solder the heavy wires near the very ends (can roll the material around the
wire diameter and solder too for a good connection), then solder two sense wires a little closer toward the center. Check with a
known current and move the two wires closer together or farther apart for calibration if desired.
For example, i made a 20 amp shunt out of a piece about 2 inches long and about 1/2 inches wide that was purchased from a hobby shop.

I've also used Nichrome wire, by wrapping a length around two bolts so i had two lengths in parallel, then tightening the bolts.
The bolts in that case were the two terminals of an analog meter that needed a current shunt to work with it.

 

[Sceadwian]

jaderosita, where are you located at? You can always order parts over the Internet if you can find a supplier that ships to your local.