240A in a 50A Hall sensor?

[treez]

Hi,
Supposing 240A goes through the ACS772LCB-050U-PFF-T Hall effect current sensor. Will it simply give an output which is at the Vcc rail?
The sensor is only meant to measure up to 50A.

ACS772 datasheet
https://www.allegromicro.com/en/pro...ed-amp-integrated-conductor-sensor-ics/acs772

Also, suppose 240A goes through this unidirectional current sensor in the wrong direction….will the current reading just indicate zero amps?

 

[wwfeldman]

Allegro is most likely to be able to answer your questions authoritatively

 

[treez]

Thanks,
It’s a case of “will the stronger magnetic field” cause some type of “saturation” in the Hall sensor?
…Or will the output voltage (of the Hall sensor device) just “rail high” at maximum output. …We hope the latter…since we don’t need to sense the current amplitude particularly, just need to sense if it goes over an amp or so in reverse.

In small companies, i have very poor experience of getting useful info out of companies, but yes we will try, but sure we will not get help.

 

[KlausST]

Hi,

In small companies, i have very poor experience of getting useful info out of companies, but yes we will try, but sure we will not get help.

The datsheets usally give all informations I need.
This is for the normal operation.

But if you want to mistreat the device... I think it's asking too much for the manufacturers to specify every possible mistreating of a device.

Klaus

 

[FvM]

if you want to mistreat the device

The datasheet is specifying several important aspects of the answer.
1. Continuous current rating of 250A
2. Pulse current rating for 1s
3. Hint to magnetic hysteresis effects of overcurrent events
4. Output saturation levels

My expectation is that you won't get output polarity reversal, at least within the specified pulse current range. But that's a simple question that can be addressed to Allegro support. If you don't get satisfying answer, perform a test on your own.

Also, suppose 240A goes through this unidirectional current sensor in the wrong direction….will the current reading just indicate zero amps?

Surely not zero but negative output saturation.

 

[treez]

Thanks, the sensor is just 100 microohms, so its not going to overheat the device.
At the end of the day we were wondering if a denser magnetic field is going to damage something in there.

We could use a higher current rated hall sensor, but its resolution at the lower currents will be much worse.

This is for sensing small amounts of reverse current where 250A of forward current would normally flow.
We dont need to detect the 250A...just the reverse current, should it ever happen

 

[wwfeldman]

i used to work for a company that did this - large current one way, small current the other

they used a high current diode in the forward direction with a small current diode anti-parallel
they added a resistor in the anti-parrallel side and could measure the reverse current using the voltage across the resistor.
both diodes were of appropriate voltage ratings.

 

[treez]

Thanks wwfeldman...i feel a bit like the "not" person though...always coming up with the "other" side......because in the reverse direction we may have large or small current flowing, but only need to know if "any" current is flowing in the reverse direction......because none should be and we will have to switch it off if it does flow in reverse.