Current measurement Shunt

[techie]

example max4081

How to make a SHUNT for 5A current measurement. The application is a power meter whereby the current from a CT is 5amps and has to be fed to a SHUNT to convert to voltage for measurement by an AD77xx series IC.

I have tried using Nichrome wire but it is not solderable. Using Iron or other metals with high R, there is a problem with high temperature co-efficent.

any suggestions

 

[cube007]

measurement shunt

Hello techie,

are you not able to use standard shunts? There are a lot of available for example from Isabellenhuette etc.
Which resistance do you need?

by,
cube007

 

[techie]

current measurement shunt

I need about 0.1ohm 5Amps.

Can you mentiond some website for these. what is the approximate cost.

 

[cube007]

max4072 shunt

Isabellenhuette (https://www.isabellenhuette.de/) has got a shunt for 1..10W with 0.1 Ohm. You can get it from www.schuricht.com for EUR 2.29/St. @ 100. There are a lot of more which could be interested for you.

by,
cube007

 

[techie]

On some websites like allied, they are avaialable for $30 or so per pc. I need 3 shunts for 1 meter. Cant afford to have them used. Afterall they are just pieces of nichrome metal which is cheap.

I dont need high precision. 1% or so is enough

 

[cube007]

You should take a look into other distributors like Farnell, etc. They all have shunts which you could use.

by,
cube007

 

[cent]

Hi,
Nichrome is used for Power resistors or Toasters.
Bad as a shunt. It has a high temp coefficient.
Constantan is better. It's a classic alloy for shunts.

But 5A is not so high. Why don't use several low tempco standard resistors in parallel instead of building a custom one ?

Regards,
cent

 

[mr_ghz]

Hi techie,

you can build your shunt also by paralleling more resistors. So you can use 10 times a 1Ohm resistor. You have a maximal power dissipation of I^2*R = 2.5W divided by 10 resistors, so each one have 1/4W --> these are standard devices.

Bye

 

[cube007]

Hi techie,

take look at the Homepage from Maxim (www.maximic.com) and search for:
MAX4080, MAX4081
MAX471, MAX472
MAX4069-MAX4072
MAX4373-MAX4375

The devices are Current Sense Amplifiers for Power Level, Battery Voltage and Current Design.

You can use them for an easy way to measure current.

by,
cube007

 

[7rots51]

hello
check www.ohmite.com or www.vishay.com
CS3 resistors from ohmite are 4 wire resistore for your purpose.
Precision Current Sense resistor with a non inductive Terminals; silver plated & tinned.

I think 0.1 ohm for shunt is too high ,you should use 0.005 or 0.010 ohm resistors,so dissipation is low at 5 amps! four wire resistors is needed for sensing the voltage across the resistor and eleminating the wire ohmic loss.

bye