Hall Effect sensor and ADC

Hardware
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Hi!

I have a hard time using ADCs (ADS1115) with linear hall sensors (49E, 3503) as they output voltage from 0.8v to 4.2v depending on magnetic flux.
Furthermore, useful linear area of this spectrum is maybe from 1.5v to 3.5v

Is there something i'm missing? Can i "remap" voltage before reading it in ADC to have full resolution range in-between 1.5-3.5v? It should never be negative and never above VCC.
I'm thinking about using op-amps, but i'm too unfamiliar with those to come up with solution.

Another problem i'm having is hall sensor output is too noisy - o-scope measures 40mv p-p with all power filtering and shortest leads - this is way above ADS1115's resolution

Schematic for implied usage:

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Grateful for all suggestion in advance!

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Welcome. Where is the schematic?

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Sorry, i didn't realize the schematic is needed. Right now hall sensor is sitting on a breadboard with VCC,GND connected and i'm reading voltage from output pin with oscilloscope.

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Updated this post with rough schematic

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Seriously, put it ALL inside a steel container to eliminate stray magnetic fields and see if the "noise" goes away. Seems like you have, at least, a floating lead, somewhere.

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The wiring diagram shows no power supply filtering. Please post a complete schematic.

The 49E sensor data sheet specifies 90 uV noise at 10 Hz bandwidth, 500 fold lower than the noise you are picking up from the environment.

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My flat doesn't have grounding, this causes some noise issues overall :slight_smile: So, everything is floating around mains voltage.
But this is a battle i can't win, but maybe there is a known way to filter and adjust output of hall sensor

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All right, antispam downed my post for a while, i stumbled upon this blog post , which explained op-amp usage in similar situation
I fired up Falstad's circuit simulator and it is almost what i need - except output voltage could potentionally go below zero or above 5V - is there a way to clamp signal? Maybe mighty op-amps could do that too?

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Regarding my original post and random schematics - i don't really think this is relevant talk, when i try to figure out something fundamental and independant of particular usage case.
Maybe i'm in a wrong category? :face_with_monocle:

Anyway, i'll try op-amps on breadboard and get back to this topic again

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That means even more RF is floating around inducing signals into your wiring. Try adding shielding and bypass capacitors to the power connection of every device. Bypass to the devices' local ground connection.

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That's what i do to every floating and battery-powered projects. LC filter helps a lot, bypass caps just before sensors

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Put a small steel (tin) can over the Hall effecto sensor. See if that changes anything. Should provide some magnetic shielding.

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How could that apply to a noisy sensor? Wouldn't that be extremely dependent on each individual application and implementation?

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Look at the noise level from main voltage line (5V from nano board). You can change voltage regulator to low noise, or make low noise supply.
I am using low noise regulator to increase noise, and temperature stability.

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