100A meter, shunt

[SentinelAeon]

I have a cheap multimeter from aliexpress but i ordered it without a shunt. I would like to measure high current and for that i need a shunt. My question is, is it possible to use a normal resistor of correct value or i need to order this exact shunt ? I added a link to the multimeter and image of how ur supposed to connect it.

multimeter aliexpress

 

[rjenkinsgb]

You need a shunt with the same resistance and the appropriate power rating.
The resistance is likely somewhere around 1 milliohm, almost certainly under 10 milliohms.

100A through 0.001 ohms = 10W; through 10 milliohms = 100W!

 

[Diver300]

Use a Hall effect current transducer. This might work:-

https://si.farnell.com/lem/hlsr-40-p-sp33/current-sensor-40a-voltage-o-p/dp/2664191

 

[ChrisP58]

A current shunt is just a low value resistor that has been optimized for measuring high currents.

They usually have 4 terminals. Since they typically have a very low resistance, there will be an error depending on where on the resistor body that the measurement is made. Building it with separate connection points for power and measurement will reduce this error. They are usually individually calibrated by cutting a notch or grinding away material on the side of the resistive element.

Shunts are usually rated by the voltage they produce at a given current. I have one that is marked 50mV/50Amp. This tells you that there will be 50 millivolts across the measurement terminals when there is 50 Amps flowing through the power terminals. Ohms law tells us that this is 1 milliohm.

 

[crutschow]

is it possible to use a normal resistor of correct value or i need to order this exact shunt ?

For the sub millohm resistance needed there is no "normal" resistor.
You either need to make and calibrate one using a piece of wire, or buy a proper 100A shunt.

Note that even a 1mΩ shunt will dissipate 10W @ 100A.

 

[SentinelAeon]

I see. I might aswel buy an original shunt from the same seller where i got the amp meter, it costs like 3$. Tnx

 

[Nigel Goodwin]

I see. I might aswel buy an original shunt from the same seller where i got the amp meter, it costs like 3$. Tnx

BY far the best idea.

 

[schmitt trigger]

Additionally, the shunt’s resistive materials are selected for low Tempco. Shunts do get warm, and a material with poor Tempco the tolerance errors may double or triple during active operation.