Hi All
I need a little advice about setting up a circuit for the following current sensor.
http://www.farnell.com/datasheets/51649.pdf
I wish to use it to measure the current running through a bus bar which will have a current between 0 to a maximum of 450A running through it, my concern is how to interface this with a microcontroller that can take a maximum of 3v3. Do I need to have an external voltage at Vref? Can I just input the output of this sensor straight to the controller via for example filters (i.e. butterworth filters) just to remove high frequency componenets.
Thanks
Art

 

The sensor output is offset by 2.5V so it can handle AC currents.
The maximum signal centered around 2.5V is ±1.875V full scale or 4.375V to .625V.
If the current your are measuring is DC then you could use a differential amp connected between the sensor output and the 2.5V reference output with some gain so that the amp output would be 0V to 3.3V (or whatever voltage you want).

 

Check out the data sheet for the Allegro ACS712, it shows some integration circuits.
Max.

 

According to the link.....only the 50 and 100 amp version is available in the bus bar configuration.

 

If you want to measure a RMS AC current in the 450 amp region a Loop-Powered, Split Core, AC Current Transmitter having a 4 - 20 mA output would have been a better sensor choice. Using one having a 500 Amp AC RMS full scale range 0 mA would = 0 Amp and 20 mA would be 500 Amps. You run the 4-20 mA loop through a for example 165 Ohm 1% resistor and now 0 Amp = 0.066 Volt and 20 mA = 3.3 Volts. Once you are there it is just a simple matter of doing the uC code to read in engineering units of Amps.

Note: The linked sensor is an Average responding sensor which is fine for sine wave applications. Should you require a True RMS sensor those are also available. Also, the link is merely an example, there are likely a dozen manufacturers making these units and likely some inexpensive versions from China. I simply linked to a manufacturer I was familiar with.

Using the sensor you have while it will work will require additional circuitry to provide your uC with a usable signal.

Ron