Low Current Sensor IC

ransiluj · Nov 15, 2012

I need good current sensor IC. I'm going to measure current change of the PC when software is running. Do you have an idea about how much current should it take. I mean the current that is changing. Using a good accurate IC is good way to measure that change of the current ? IC like ACS 712 is good or bad?

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or is there any current sensing IC for measure micro current change or mA change?

Tahmid · Nov 15, 2012

What is the range of current you need to measure? Also, what is the required accuracy?

ransiluj · Nov 15, 2012

highest value of the current is 4A. change of the current is not so sure. That range maybe mA range or a micor ampere range. Is there such accurate ICs available ? like hall effect ICs??

varunme · Nov 15, 2012

ransiluj , I think you need a current sensor with high rating with more resolution isnt it ?

ransiluj · Nov 16, 2012

you are right could you please help me on that?

Tunelabguy · Nov 16, 2012

ransiluj said:
highest value of the current is 4A. change of the current is not so sure. That range maybe mA range or a micor ampere range. Is there such accurate ICs available ? like hall effect ICs??

If you are trying to measure the change in supply current due to running this or that software then I think those changes will be swamped out by other unrelated variables. For example, every time you move an optical mouse, the mouse wakes up its LED and that takes more current. When some background program causes disk accesses that make the arm move across many cylinders then that takes more current. How far the disk arm needs to seek and how often are essentially random and are not correlated to running some specific piece of software. Another variable is wi-fi. The wi-fi transceiver takes more or less current depending on the number of packets sent and the signal strength to the router. Packet retransmission can be affected by Internet congestion - again something that is out of your control and uncorrelated with running specific software. I'm sure if I thought about it more I could come up with even more random factors that affect supply current. So I don't think there is much value in finding a current measuring technology that measures 4 Amps to a precision of microvolts and correlating that with running specific software on the PC.

gehan_s · Nov 16, 2012

Tunelabguy said:
If you are trying to measure the change in supply current due to running this or that software then I think those changes will be swamped out by other unrelated variables. For example, every time you move an optical mouse, the mouse wakes up its LED and that takes more current. When some background program causes disk accesses that make the arm move across many cylinders then that takes more current. How far the disk arm needs to seek and how often are essentially random and are not correlated to running some specific piece of software. Another variable is wi-fi. The wi-fi transceiver takes more or less current depending on the number of packets sent and the signal strength to the router. Packet retransmission can be affected by Internet congestion - again something that is out of your control and uncorrelated with running specific software. I'm sure if I thought about it more I could come up with even more random factors that affect supply current. So I don't think there is much value in finding a current measuring technology that measures 4 Amps to a precision of microvolts and correlating that with running specific software on the PC.

yes we have already taken into account all the things you said and more. for your information when we test the software no mouse or keyboard movements will be done. we take power measurments before the software runs to estimate the initial power draw from the PC. we will test the software under cetrain loads as well. we still havent taken the initial current, voltage measurments due to some reasons. so we desided to go ahead and do the research part any way.

ransiluj · Nov 19, 2012

is there anyone who can help us? please!!

FvM · Nov 19, 2012

Are you talking about standard (ATX) benchtop PC? It has multiple supply voltages. Which do you want to monitor?

ransiluj · Nov 19, 2012

yes i'm talking about this standard becntop PC. I want to monitor change of the main supply cuurent changes. Which means current coming from the main supply to the computer power supply.

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and you can tell me what is most accurate way to measure the current.
1.using hall sensor
2.using a current sensing resistor.
what is the most appropriate way?

Tahmid · Nov 19, 2012

ransiluj said:
and you can tell me what is most accurate way to measure the current.
1.using hall sensor
2.using a current sensing resistor.
what is the most appropriate way?

Without knowing the exact specifications and parts being used, in general, hall effect sensors are more accurate than current sensing resistors.

ransiluj · Nov 19, 2012

as i told you before my highest value that we going to measure is 4A and we need to measure small current changes. Those current changes are in micro ampere range.

Tahmid · Nov 19, 2012

I don't think you're going to get much precision/accuracy in the microampere range, using a shunt resistor especially one that has to be used to measure up to 4A. Imagine how small the voltage changes would be.

ransiluj · Nov 19, 2012

Then do you have a idea about good hall effect sensor that measure such small change of the current. If you know please let me know.

ransiluj · Nov 20, 2012

is there anyone who can help us? please.

FvM · Nov 20, 2012

as i told you before my highest value that we going to measure is 4A and we need to measure small current changes. Those current changes are in micro ampere range.

I doubt that input current changes in a ppm scale are significant. Mains voltage fluctuations will cause larger variations without actual load changes. If you want to measure power consumption on the AC side, you need to make a very accurate real power measurement, e.g. using an energy meter chip. It may be still dwarted by supply voltage variations if you are really looking for ppm order of magnitudes.

It's not primarly a problem of current sensing methods, but current transformers are the first choice for AC measurements for many reasons.

A more promising setup could use an ATX supply with DC input, powered by a regulated DC source or a battery. The other option is to measure on the DC side of ATX supply, which would at require to monitor at least 12V core supply and possibly 3.3V and 12V peripheral voltage.

I also agree to the systematical doubts mentioned by Tunelabguy. It's not a matter of mouse movements. There are arbitrary actions of the windows OS (e.g. time scheduled) that can be hardly predicted. But a statistical approach should be able to eleminate these effects by repeated measurements. Statistical methods can also tell about the achieved significance.

dick_freebird · Nov 20, 2012

Touchstone has some current sense ICs that go down to uA.
I would say you can use these, and perhaps a few of them
across different shunt legs of a composite sense resistor
(or a measured PCB trace's resistance) to get different
ranges.

For that matter a pair of 'scope probes and export the
difference waveform to Excel, might be like a freebie
if you can stand only 8-bit resolution. Tap the trace
at two spots, and use the measured point to point
resistance to scale the measured voltage.

ransiluj · Nov 21, 2012

FvM said:
I doubt that input current changes in a ppm scale are significant. Mains voltage fluctuations will cause larger variations without actual load changes. If you want to measure power consumption on the AC side, you need to make a very accurate real power measurement, e.g. using an energy meter chip. It may be still dwarted by supply voltage variations if you are really looking for ppm order of magnitudes.

It's not primarly a problem of current sensing methods, but current transformers are the first choice for AC measurements for many reasons.

A more promising setup could use an ATX supply with DC input, powered by a regulated DC source or a battery. The other option is to measure on the DC side of ATX supply, which would at require to monitor at least 12V core supply and possibly 3.3V and 12V peripheral voltage.

I also agree to the systematical doubts mentioned by Tunelabguy. It's not a matter of mouse movements. There are arbitrary actions of the windows OS (e.g. time scheduled) that can be hardly predicted. But a statistical approach should be able to eleminate these effects by repeated measurements. Statistical methods can also tell about the achieved significance.

thank you very much for the help

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dick_freebird said:
Touchstone has some current sense ICs that go down to uA.
I would say you can use these, and perhaps a few of them
across different shunt legs of a composite sense resistor
(or a measured PCB trace's resistance) to get different
ranges.

For that matter a pair of 'scope probes and export the
difference waveform to Excel, might be like a freebie
if you can stand only 8-bit resolution. Tap the trace
at two spots, and use the measured point to point
resistance to scale the measured voltage.

thank you for the help

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FvM said:
I doubt that input current changes in a ppm scale are significant. Mains voltage fluctuations will cause larger variations without actual load changes. If you want to measure power consumption on the AC side, you need to make a very accurate real power measurement, e.g. using an energy meter chip. It may be still dwarted by supply voltage variations if you are really looking for ppm order of magnitudes.

lot of energy meter chips have to program using another evaluavation board. That is the problem we are facing when using energy meter chip. For that we need to spend some more money and our budget is going high. If there is no programming chips are there that will be very useful to us. I search on those chips but we didn't found any.

Low Current Sensor IC

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