Difference between Hall current sensor and small resistor to measure current

[San_Pandey]

Hello everyone,
I have a doubt regarding current sensing method.
Why can't we measure current using small resistance all the time? Why to buy hall sensors for that? Is there any concept behind that which I am not aware of ?

 

[KlausST]

Hi,

Hall sensors are not electrically connected to the wire you want to measure the current. --> it is an isolated measurement method.

There are so many applications where you want to measure current.

With different voltages, currents, frequencies...
Therefore you need much more informations to select whether to use shunt method or hall method.

****
For a silicon production we measure currents up to 6000A RMS with isolated voltages up to 2500V RMS ... hard to do with a shunt.
The wire is a copper pipe (inside cooling water) with diameter of about 100mm.

Klaus

 

[smijesh]

Resistor or shunt current sensing method is not reliable. Resistance of the shunt will increase when more current flowing (increase in temperature due to I^2R loss).

 

[KlausST]

Hi,

Resistor or shunt current sensing method is not reliable. Resistance of the shunt will increase when more current flowing (increase in temperature due to I^2R loss).

This answer is too genral.

I don´t see why using a resistor should not be reliable.
The tempco of bought shunts will not be worse the tempco of hall sensors.

It seems you are referring to copper traces of a PCB. Here I agree that this is not a precise solution.

But if you buy a shunt then the datasheet tells the specifications. The same is with hall sensors. Please compare some datasheets.

*****
Even the table does not meet my experience.
* I can´t see why the shunt method should have lower bandwidth than the hall method.
* power supply depends on circuit (I don´t think there is a general answer)
* size depends on circuit (I don´t think there is a general answer)

Klaus

 

[davoud]

I am agree with Klaus,
I think Shunt resistor is very high precise, reliable and fast response than the other, but it is not isolate.

 

[smijesh]

Shunt resistors are not prices for medium or high current application because temperature of shunt will vary the resistance hence voltage variation across the shunt

Shunt resistors are not reliable because if the rated current is exceeding by 30% shunt resistor may burn, continues current will cause reduction in mechanical strength due to oxidation

 

[chuckey]

" Shunt resistors are not reliable because if the rated current is exceeding by 30% shunt resistor may burn, " If you over dissipate any component you are likely to shorten its life. Manufacturers have worked out the life of components at a certain level, exceed it at your peril!
Frank

 

[KlausST]

Hi,

yes, I wonder how many hosehold devices are "reliable" when they are powered with 300V instead of 230V.
Especially transformers and capacitors may not be reliable enough...

I tested the hall sensors, but was not satisfied with the precision. But to be true I did no research about new - better - devices for years now.
Therefore I either use shunt (up to several 10A RMS and some 100A pulse current) or ready to buy current transducers (LEM) up to 6000A RMS.

And yes, the shunts are more sensible to short circuit currents.. they may die, if not properly dimensioned (I^2t).
But the current transformers suffer from remaining offset current after an overcurrent pulse. To maintain DC accuracy they need to be calibrated from time to time.

Klaus

 

[c_mitra]

You mention that shunt has very low size and Hall sensors have simply low

I do not agree. A four terminal shunt cannot be very low in size (compared to a Hall sensor that can be even a SMD part).