A bit of reverse engineering! I have bought a couple of different Crankshaft sensors (BMW types) which have 3 pins, and which I believe to be Hall sensors. They have a built-in magnet, and are supposed to output a digital signal with frequency proportional to the change in magnetic field strength from a toothed steel wheel.
I want to interface these with an engine ECU that can receive the digital signal, of 5volts or 12 volts.
Not having or being able to find any info on the pin designation, I have tried all combinations to identify the correct one to get a digital output to no avail. The 3 pins are supposed to be as follows: Power, Ground and signal. I have also tried using a pull-up resistor in case the output is 'open collector' to no avail. When placing a piece of steel to it, I can get a small response from one sensor where one wire changes state between 0.7 volts and 0.1 volts approx but cant get at least 5 volts by any means.
For those not familiar with automotive digital hall sensors they comprise a permanent magnet, a hall sensor, followed by a high gain amplifier, then a Schmitt trigger at the output.
Have I missed something in my attempt to get an output?