# Current Sensor Question

Discussion in 'The Projects Forum' started by BramLabs, Apr 14, 2016.

1. ### BramLabs Thread Starter Member

Nov 21, 2013
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5
Hello Sir,
I want to ask, what current sensor work best for sensing 10 - 40 Amp ?
Does ACS712 can handle sensing current about 10 - 40 Amp ?
And if can, how about the voltage, let's just say i want to sense electrical motor that can drive voltage up to 36 V and 34 Amp (Generally, the motor only consume about around 20 V and current, let's just say 10 - 40 Amp, and it depends on the acceleration).

I have read the datasheet but i didn't understand all of the information in it.
What's the difference between the information below ?

Thank you so much sir !

2. ### ErnieM AAC Fanatic!

Apr 24, 2011
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The devices have different sensitivities to scale them for different currents. The lower sensitivity is used for the higher currents.

The -05 is no good for 40 amps where it will give a 7.4 volt output, which it cannot do with a 5v supply. Either of the other two should work.

These parts have an internal isolation of over 2,000 volts. The way you wire this in will probably reduce that limit.

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3. ### BramLabs Thread Starter Member

Nov 21, 2013
93
5

So how to choose the 'mode' of the configuration sir, if i want to use x05B or x20A or x30A ?
Is that based on the current that we want to sense ?
So, if i want to sense around 30A, it will give output 2.64 Volt ?
And if i want to sense around 5A, it will give output 7.4 Volt but it needs supply more than 7.4 Volt ?

So sir, what i'm understand is that, the more current i want to sense (in this example more than 5 amps or 20 amps) the lower sensitivity i get, BUT the lower current i want to sense (in this example, let's just say 5 amps or 20 amps, the higher sensitivity i get ?

Thank you sir

4. ### ErnieM AAC Fanatic!

Apr 24, 2011
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That is what it is, higher currents need a lower sensitivity. It's a classic engineering compromise due here mainly to the constraint of a 5 volt max output.

Whatever range you measure you need to keep the output below 5 volts. Now you do want to use the highest sensitivity you can to get the best measurement just avoiding the 5v limit.

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5. ### BramLabs Thread Starter Member

Nov 21, 2013
93
5
Oh i know sir now. I thought that this ACS712 have 3 mode configuration. But it have 3 different option of IC. 1 IC for sensing up to 5 amps, another is for 20 and the last is for sensing 30 Amp.
I thought that in 1 IC, we can choose whether to sense 5 amps, or 20 amps or 30 amps.

Thank you so much sir

6. ### absf Senior Member

Dec 29, 2010
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356
I knew what you're thinking. When I looked at the datasheet of that chip, there is not such a pin called "MODE" or "SELECT". So I just want you to figure it out yourself.

Allen

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7. ### ErnieM AAC Fanatic!

Apr 24, 2011
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This chip comes in three versions.

You choose the sensitivity by which version of the chip you purchase.

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8. ### Alec_t AAC Fanatic!

Sep 17, 2013
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You said you wanted to measure 10-40A. None of those chips has a specified 'Optimised Accuracy Range' extending beyond 30A, so it's unclear what error you would get when measuring in the 30-40A range.

9. ### BramLabs Thread Starter Member

Nov 21, 2013
93
5
Do you have any recommendation sir for the current sensor that can sense up to 40 A ? I'm new and even never use current sensor before. Thank you sir ^^