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asimov_18
04-26-2008, 03:01 PM
Hi guys,
Generally when ever we are measuring DC current flowing in circuit. we generally put a small resistance(high precision) in the circuit and measure the voltage across that resistor which gives the value of the current in terms of the voltage in terms of voltage as V= IR....But there are some draw backs with this approach...the sensing resistor always dissapates some power(after all it's a resistor ).

The best way to reduce the power dissapation thru this resistor is to choose a small value of this resistor but this is again problematic as as getting precision resistor is expensive and if the current flowing thru the circuit is samll then the volatge developed across the resistor is small and measuring it using ADC can be challenging....

Is there any other alternative methord to measure DC currents...

I think one way is to use hall sensors .....but it will require magnetic shelding and elaboration.....any other way I am missing on.....which might be cheap and effective...???

superchiku
04-26-2008, 07:23 PM
i think the multimeter can do that isnt it???

you just have to connect the 2 leads of the multimeter to the 2 leads of the wire and make the circuit closed and the multimeter will measure the current.......

docel
04-28-2008, 05:26 AM
We have plenty of those instruments: Inductive coupling, inductive eddy current sensors, micro-magnetic cantilevers, IR scan current to temperature sensors, Atomic Force Microscopy assisted conductivity scanners..............
Most of these technologies are hitech industrial-research instruments beyond the scope of the ordinary and are aimed at micro and nano current targets.

attrish
05-09-2008, 05:39 PM
We have plenty of those instruments: Inductive coupling, inductive eddy current sensors, micro-magnetic cantilevers, IR scan current to temperature sensors, Atomic Force Microscopy assisted conductivity scanners..............
Most of these technologies are hitech industrial-research instruments beyond the scope of the ordinary and are aimed at micro and nano current targets.


just check outthe cheap solution ACS704 current sensors from Allegro Microsystems Inc.

docel
05-09-2008, 07:37 PM
[quote=docel]
just check outthe cheap solution ACS704 current sensors from Allegro Microsystems Inc.

CHEAP solution :?:
What do you mean :!: :!:

They are neither 'cheap' nor 'simple'.........

attrish
05-09-2008, 07:53 PM
Is there any other alternative methord to measure DC currents...

I think one way is to use hall sensors .....but it will require magnetic shelding and elaboration.....any other way I am missing on.....which might be cheap and effective...???

well this the story cheap and effective solution for dc current measurement



Most of these technologies are hitech industrial-research instruments beyond the scope of the ordinary and are aimed at micro and nano current targets

N this was urs..................................but ACS704 is cheap n can measure current up 15A.......................upto 150A.

Still m missing somthing :?:

attrish
05-09-2008, 07:53 PM
Is there any other alternative methord to measure DC currents...

I think one way is to use hall sensors .....but it will require magnetic shelding and elaboration.....any other way I am missing on.....which might be cheap and effective...???

well this the story cheap and effective solution for dc current measurement



Most of these technologies are hitech industrial-research instruments beyond the scope of the ordinary and are aimed at micro and nano current targets

N this was urs..................................but ACS704 is cheap n can measure current up 15A.......................upto 150A.

Still m missing somthing :?:

docel
05-09-2008, 08:07 PM
attrish: You sure have missed something.
Asimov wants something other than Hall sensors as he knows that it is neither simple nor cheap.
The ACSXXX is NOT a cheap method of measuring currents. It is a precision device and needs critical techniques (translate =expensive).

Just read the datasheets of that obsolete Ic ....

asimov_18
05-16-2008, 12:35 AM
Hi fnds
thanks for the tremendous response.......well let me describe the problem a little better.......I have to charge a Li-ion batter (of type 18650) using a solar pannel.....as we all know that li-ion battery are charged in two stages in the first phase we charge the battery using constant current(with max value about 1c) until the battery voltae reaches a precise battery voltage of 4.2(+/- 1% tolerance) following which we follow a constant volatge charging(@ 4.2V) until the charging current drops to 0.1C
so to charge a battery I need to connect a serries resistor (precision resistor of small value) and measure the voltage across that resistor to estimate the charging current(using I = V/R)..now the problem is that I am charging this battery using a 4.5V 220mA solar pannel so the efficiency is really important I dont want to us the serries resitor to measure the charging curent( as the resistor would have wasted some power and if I use a small resistor ,measuring voltage using ADC would be hard)any suggestions / alternative.........any suggestion on the same would be welcome...


asimov

docel
05-17-2008, 10:54 PM
1. You cannot charge a Li-ion or Li-poly battery on a 4.5V solar cell.
2. The Forum does not mind helping others with THEIR personal problem-solutions, but it is your duty to be plain , frank and open.
Besides , this is off topic and must belong in the appropriate Forum.

Sorry, but there must be some context in ones question.