# Current Sensor Question

#### BramLabs

Joined Nov 21, 2013
98
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 !

#### ErnieM

Joined Apr 24, 2011
8,382
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.

#### BramLabs

Joined Nov 21, 2013
98
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.

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

#### ErnieM

Joined Apr 24, 2011
8,382
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.

#### BramLabs

Joined Nov 21, 2013
98
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.
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

#### absf

Joined Dec 29, 2010
1,968
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

#### ErnieM

Joined Apr 24, 2011
8,382
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
This chip comes in three versions.

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

#### Alec_t

Joined Sep 17, 2013
14,409
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.