working with ACS712 (current sensor)

[kookooli]

Hi
I'm working with an ACS712 current sensor.
my problem is here:
sensor's output voltage when it is not measuring is not constant.It varies from 2.3 to 2.5.
but it should be fixed 2.5.
what can i do to make that value constant ?

 

[FvM]

Check the supply voltage.

 

[kookooli]

Check the supply voltage.

My supply voltage is aproximately constant but i dont know why sensor's voltage varies ?
what can I do ?

 

[ravindragudi]

The schematics of your application with the sensor will help to look into why the output varies.

 

[schmitt trigger]

My supply voltage is aproximately constant but i dont know why sensor's voltage varies ?
what can I do ?

Please define: "aproximately constant". Is it 5V +/- 1%, 5%, 10% or what?
An ACS712 output voltage is ratiometric to the input voltage, as described on page 9 of the datasheet:

Ratiometry. The ratiometric feature means that its 0 A output, VIOUT(Q), (nominally equal to VCC/2)

If your output voltage varies without any magnetic fields, then your input voltage must be varying too.

 

[kookooli]

Please define: "aproximately constant". Is it 5V +/- 1%, 5%, 10% or what?
An ACS712 output voltage is ratiometric to the input voltage, as described on page 9 of the datasheet:

Ratiometry. The ratiometric feature means that its 0 A output, VIOUT(Q), (nominally equal to VCC/2)

If your output voltage varies without any magnetic fields, then your input voltage must be varying too.

Supply voltage is 5.1 volt (5.08 to 5.13 max changes) but sensor's voltage varies from 2.4 to 2.7
what can I do ?

 

[FvM]

Supply voltage is 5.1 volt (5.08 to 5.13 max changes) but sensor's voltage varies from 2.4 to 2.7

How do you measure it? Are you sure that no current is flowing through sensor?

 

[kookooli]

How do you measure it? Are you sure that no current is flowing through sensor?

I want to measure the output current of a switching power supply via ACS712.
when the switching power supply is not connected to it's supply (220 volt/50 Hz) i measure the sensor's voltage that should be Vcc/2. but it is not and it changes in a spread range from 2.4 to more that 2.7 .

 

[schmitt trigger]

If you have no other problems (i.e. solder joints) then you have either a defective device or you have stray magnetic fields affecting the sensor.

 

[FvM]

You didn't answer "How do you measure?". I have to assume that you are using a sufficient accurate measuring method, not a µC ADC, not an oscilloscope that displays wideband sensor noise.

 

[zsolt1]

hi ,
i'm also trying to get that cip for some industrial application... Do you have a factory made module or you made the circuit yourself? It's clever to check it's power supply . Personally i encountered the problem that i could not calibrate some sensors supplied from a common SMPS power supply (12v/2A) , instead everything worked perfectly when i used 12V lead acid battery ... so it was an EMI issue in the end. Also it's clever to check somehow near by fields since the cip uses Hall sensor as current sensor. You could try to shield that part of the circuit with some steel plate/box.
Ps: does somebody know where to get those modules from EU region ?