Types of hall effect sensors

Hi, I have several types of Hall effect sensors and I'm hoping someone might be able to help explain the difference between them. I'm having trouble understanding the datasets properly,

Are both digital? do they have the same distance between magnet and sensor to activate?

Hall A3144 - uni-polar? state is only changed when under the effect of the magnet?

Hall U18909 - bipolar latch type - bi polar - Can detect either magnetic polars? - latch type - state is either high or low and is change by the magnet (north pole for on, south pole for off?)

other types available?

Here's a simple overview.. your hall effect sensors only detect magnetic fields.

The difference with the bipolar latch type is that there are additional circuitry built in. 1st it senses whether there's a north pole or south pole using a Schmidt trigger comparator to steady the trigger point. When a North pole is detected it latched as a HIGH- latching means that it will retain this HIGH value even when the magnetic field is removed. It will remain high until a South pole is detected. This type of circuit has "memory" and may be used as a switch or flip flop.

This latching is useful in some situations but not in others.

The A3144 detect a magnetic flux regardless of pole and trigger a LOW. When the magnetic field is removed it will go to high based on the pullup. It also has a Schmidt trigger to help it not to oscillate. It is useful to a RPM sensor that uses one magnet.

There is one more hall effect type which is the ratiometric sensors that measures magnetic gauss. The previous sensors had comparators built into output a HIGH or LOW the ratiometric sensors measure the strength of the magnetic field.

A magnetic compass might be considered a hall sensor which gives you the direction of the magnetic field. Magnetism is a very interesting topic and hope you come up with some interesting projects using them.

The A3144 will detect a magnetic flux regardless of pole and trigger a HIGH.

The A3144 is sensitive to only one pole (N or S, the data sheet that I have does not specify). Confirmed, just now, by connecting an A3144 to my Uno.

The A3144 is sensitive to both N and S but it depends on which side of the sensor you are detecting the magnet... thanks for bringing that up @groundFungus. I've also corrected the output being Low needing a pullup for this sensor.

Just for reference, I use a A3213EUA-T Hall sensor as switch. It doesn't matter which pole approaches from which side, it acts regardless, it doesn't latch and is usable on 3.3.VDC. Once magnetic field is gone, it goes HIGH again.

I use it in my GPS project to switch logging on after a certain period.