ACS758 current sensor

Other Hardware Sensors
1

Hi.

I´m working with a ACS758LCB-100B (100A./ Bidirectional/ 20 mv/A sensibility).

When I have to measure a current of 0.90A (DC) i get on Arduino (analogRead ()) the value 400 (0-1023). The Reference Volts= 5V.
At repose i get vcc / 2 (530). The value decreases instead of increasing although you change the direction of the current. This is not really a problem because internally in Aurduino I solve this.

I get on analogRead () the difference: 530 (repose) -400 (0.90A current) = 130) which is very high for this sensitivity (20mv/A)

Really I don´t understand why the measured value does not correspond to the sensitivity. Should be somewhat less than 20mV.

Then i use the formula:
Amp = (512-analogRead (0))*vcc/1024/0.02-0.02

Can anyone help me?.

Thanks and and sorry by my english.

2

530*1LSB @Vref=5V corresponds to 2.588V, wich corresponds to 4.395A...
I think that is the normal accuracy at that sensitivity...
have u read the datasheet regarding accuracy?

what happens when u use different currents?
like 1A, 2A, 0A, -1A, -2A?
the value for 0A seems to drift inspite of self-calibration on my ACS7xx-s...

r u sure that Vref is 5V?

did u get the current direction right?
there is IP**+** and IP**-**...

Amp = (512-analogRead (0))*vcc/1024/0.02-0.02

why do u subtract "-0.02" in ur formula?

3

Your value of 530 with no current looks out of tolerance to me. The offset voltage at zero current and +5V supply is supposed to be +/-5mV typical at 25C, and you are reading (530 - 512)/1024 * 5V = 88mV.

  1. Do you have a 0.1uF decoupling capacitor between Vcc and ground of the device, as specified in the data sheet?

  2. Are you powering the Arduino from the USB port or from an external supply? A computer USB port doesn't the most stable source of power.

  3. Are you certain that you are reading from the correct analog input pin?

4

Hi friends.

The problem is already solved.
I used two diferent sources. One for Arduino and one for the sensor y load.

With this configuration forced me to join the GND, and here was the problem. Now the Arduino and the sensor use an external source and load another.
The measurements are correct:

Load 1A= 23mv.
Load 3.20 A = 67mv
Load 4.20 A = 90MV.

Thank you both.

5

90MV.

I assume 90 mV :slight_smile:

6

hello friends.

I have a current sensor ACS758ECB 200B (200 amp Bi), and now my question is:

Does this sensor reads the waveform of a current signal?, Or just the RMS value of the analog signal?

Because I need to capture the entire waveform signal from the mains current phase.

thanks ... and sorry for my English

7

The output voltage from the sensor reflects the instantaneous value of the current, with a delay of only about 4 microseconds. So you can read the whole waveform.

8

Thank you for your answer dc42

And one last question ...

According to the datasheet (ACS758ECB-200B), my current sensor measures current + -200 amps Peak-Peak, am I correct?

9

boganazhapa:
According to the datasheet (ACS758ECB-200B), my current sensor measures current + -200 amps Peak-Peak, am I correct?

Yes. It won't be very accurate at low currents, so if the current you want to measure is well below 200A peak then you should use a different sensor.

10

Hello friends
i need connect a sensor acs758 lcb100b to arduino.

please, somebody can explain how connect and read values ?

VCC to 5v
gnd to gnd
viout to pin analog from arduino
IP+ / IP- to electric

i have a question:
not need any other element ?? like electrical resistance ?

Thank you

Jorge

11

Good day guys

I have a question. Did any of you ever tested either the 712(30A) with an actual current of eg 28A or the 758(200A) with a current of 200A? Doesn't the Sensor get hot?

Regards