# problem with my ratiometer hall sensor

Discussion in 'Sensors and Actuators' started by vamsee, Feb 9, 2013.

1. ### vamsee

36
0
Jan 10, 2013
Hi!!

I am using this hall sensor http://docs-europe.electrocomponents...6b80d88153.pdf
i got 2 problems:

1. When i vary the magnetic field, the hall sensor is acting like digital, i mean, it showing either high value or low value... Its not varying linearly as the distance between the magnet and sensor varies.

2. The quiscent voltage of this sensor is 2.5V (that is, the hall voltage must be 2.5V without the magnetic field), but it showing 0.7V.

I am playing with this voltage only, when i bring the north pole of the magnet near to the sensor, the reading is 0.1V and moves away it showing 0.7V (like digital)

Thanq

25,497
2,838
Jan 21, 2010

36
0
Jan 10, 2013
4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,838
Jan 21, 2010
My first guess from looking at the specs is to drive it into a load. Since it talks of the chip sinking and sourcing 1mA, I'd load the output using a pair of 3k3 resistors to the supply rails.

This is just a random guess

Then I would look for changes in voltage at the output as a large magnet is moved toward the device.

I suggest a large magnet because the field will increase in strength at a slower rate.

5. ### vamsee

36
0
Jan 10, 2013
hi steve!! thanx for the reply..

Actually i have 2.2kohm and 1kohm resistors, so i shud connect them in series (3.2kohm) across output of the hall sensor and gnd.. Am i correct? ( sorry, i am beginner in electricals )...

and that was good suggestion, i will try with bigger magnets as u said...

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,838
Jan 21, 2010
you want 3k3 (or thereabouts) from the output to +5V and the same resistance from the output to gnd.

You want a physically larger magnet (not necessarily stronger)

The strength of a magnetic field follows an inverse square law, but this only applies when the distances are such that they are large compared to the poles of the magnet. When you get closer, the field strength no longer varies in proportion to the square of the distance.

7. ### vamsee

36
0
Jan 10, 2013

shud i connect like this?

can u tell me, why 3.3kohm and it does to get the continous signal like analog ?

Last edited: Feb 12, 2013