siqu
Posts: 26
Joined: Thu Apr 11, 2013 1:50 pm

What would you use ??

Fri May 17, 2013 4:24 pm

Hi all.

Im thinking, why all current meters use shunt resistor and not hall effekt sensor ?
By the way, that is the difference.

If you should build a current meter that can measure up to 1 A dc, what would you use ?

Thanks

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redhawk
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Re: What would you use ??

Fri May 17, 2013 5:11 pm

I'm guessing the hall effect sensor isn't used much because it's probably not practical and not very accurate when compared to the shunt resistor method.
If I wanted to measure 1A of current I would use an analogue meter with a 10A setting or build a voltage comparator circuit using op-amps (like an LM358N).

Richard S.

siqu
Posts: 26
Joined: Thu Apr 11, 2013 1:50 pm

Re: What would you use ??

Fri May 17, 2013 8:11 pm

Hi and thanks for reply.

Is it the only reason to use a shunt resistor and not hall effect sensor.

johnf
Posts: 30
Joined: Fri Dec 23, 2011 10:35 pm

Re: What would you use ??

Fri May 17, 2013 9:24 pm

Hi, siqu.
A current meter has to offer a very low resistance to the rest of the system, and the low resistance shunt connection is traditional, cheap and effective.
The small voltage drop across the shunt resistor, which could be a massive bar of metal ( for large currents) provides a linear signal which can be sensed and amplified if necessary.
A Hall effect element could either a) sense the magnetic field around the power cable,
or b) be configured to carry the current, or a fraction of it , and a permanent magnet be applied so as to produce a Hall voltage.
Where AC power is concerned, current transformers , with insulated coils and ferrite cores , are in widespread use.
An important design consideration is, whether there is a need to have isolation between the measuring circuit and the operating circuit. This might rule out the simple shunted meter option.

siqu
Posts: 26
Joined: Thu Apr 11, 2013 1:50 pm

Re: What would you use ??

Fri May 17, 2013 10:05 pm

johnf wrote:Hi, siqu.
A current meter has to offer a very low resistance to the rest of the system, and the low resistance shunt connection is traditional, cheap and effective.
The small voltage drop across the shunt resistor, which could be a massive bar of metal ( for large currents) provides a linear signal which can be sensed and amplified if necessary.
A Hall effect element could either a) sense the magnetic field around the power cable,
or b) be configured to carry the current, or a fraction of it , and a permanent magnet be applied so as to produce a Hall voltage.
Where AC power is concerned, current transformers , with insulated coils and ferrite cores , are in widespread use.
An important design consideration is, whether there is a need to have isolation between the measuring circuit and the operating circuit. This might rule out the simple shunted meter option.
Hi and thanks for reply.

So a few god arguments to use shunt instead of hall effect sensor is:

They are to big (space)
They are common used for high current and AC where shunt is used for smaller dc circuits ?
Shunt dos not need to have isolation (every time) depend on the circuit ?

Thanks again.

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