Current Sensor threshold and monitoring

[arthurartmaster]

Hi all I am using the following current sensor:

https://uk.farnell.com/lem/hais-400-...meResp=All&searchView=table&iscrfnonsku=false

Datasheet:
https://www.farnell.com/datasheets/51649.pdf?_ga=1.141388658.194281532.1473847905

I will be measuring currents in the range of 500A to -500A, and I want the output of this sensor to go to a microcontroller (ADC), with a limit of 3v3, my concern is that the output of the current sensor may go over this limit? Can anyone let me know if this happens.

In addition to this I am using two compartors, the first compartor notifies me if the current is at 500A and the second notifies me if the current is at -500A, now I also need reference voltages for these to compare the output voltage of the current sensor any guidance would be greatly appreciated. How should I develop these reference voltages should I use a TL431, I am little unsure on what resistors to use.

Thanks

Art

 

[ericgibbs]

hi art,
A TLV LTSpice zip.

E

 

[arthurartmaster]

hi art,
A TLV LTSpice zip.

E

Is the TL431 the best way you to get the result I am after?

 

[Cicero]

Woah, out of interest whats potentially taking 500A?

 

[ericgibbs]

hi A,
Ref your PM for a lower than 2.5V ref , look at the TLV431 PDF.
E
I posted the TLV zip earlier.

 

[ChrisP58]

I will be measuring currents in the range of 500A to -500A, and I want the output of this sensor to go to a microcontroller (ADC), with a limit of 3v3, my concern is that the output of the current sensor may go over this limit? Can anyone let me know if this happens.

Art

What microcontroller are you using, and what input protection does it already have? What is it's input impedance, and how high of a source impedance can you live and still get reliable ADC numbers?

Most microcontrollers already include input protection circuitry, but only up to some finite current. As long as you can keep any fault current below that limit, you shouldn't need anything more that a series resistor. But putting to much resistance can degrade ADC performance.

So, to give you the best recommendation, we need more information. A schematic of the rest of the circuitry would help.

 

[MikeMl]

I am guessing that you are getting the HAIS400P. In that case +-600A would produce 2.5V+-0.625*600/400 = 2.5V+- 0.9375V = 1.5625 to 3.4375.
Since the max positive voltage you can measure with your 3.3V ADC is ~3.3V, working backwards, you could measure 400*(3.3-2.5)/(0.625*Ip) = 512A . By putting a current limiting resistor between the OUTPUT pin of the sensor, and the ADC input, you could tolerate an overload.

You are aware that you will always have to read the REF pin followed by reading the OUTPUT pin with the ADC (two sequential readings)?
The net current is proportional to the net difference between those readings.

 

[AnalogKid]

There is no need for a separate reference. The sensor provides a reference voltage output, so you can buffer that for the comparators to use.

ak

 

[ronsimpson]

(ADC), with a limit of 3v3,

The current sensor was built to work with a ADC running on 5 volts.
Put a two resistor divider on Vref, so that 2.5V gets divided down to 3.3/2. (1.65 volts)
Put the same divider on OUTPUT so the 0 to 5V is divided down to 0 to 3.3V.
Now the two outputs will match your 3.3V ADC.

You could put a "pot" on OUTPUT and turn down the knob until zero current reads 1.65V or the center point of the ADC.