Moutning magnetic hall sensor in steel holder?

[JonathanK]

Hello all greetings

I am converting an engine from using VR sensors to Hall sensors. I have the proper sensor which is a fully threaded aluminum housing that will go into where the former VR bosch sensor mounted (with a tab to hold the old sensor down). The part I machined is like the old sensors profile, 17mm shank and a tab coming off to hold it in, except its threaded for the new sensor down the center.

Is it ok to mount the hall, which has a magnet in it, in a ferrous steel holder? I didn't have aluminum of the right size to perform this task so I used 1018 steel which is magnetic.

The manufacturer mounts Hall sensors in an iron block on another engine, so I don't think this should pose a problem but I am unsure.

Thoughts?

 

[MikeHalloran]

>>>I am converting an engine from using VR sensors to Hall sensors<<<

Why?



Mike Halloran
Pembroke Pines, FL, USA

 

[JonathanK]

Mike,

I am switching the engine from a batch fire fuel/wasted spark setup to a fully sequential setup due to fuel injector size increase. I am running another engine management which will permit the use of hall sensors. I've determined the original VR sensors in the camshaft position are unable to provide a clean signal below 2000 engine RPM. BMW, the manufacturer of said motor, switched to a hall sensor in this position in the year after this one. I would retrofit their sensor except they also changed the camshaft and toothed wheel style as well due to VANOS (variable valve timing).

So, in short, I am retrofitting my own sensor, Cherry GS100502.

 

[MikeHalloran]

They may have changed the toothed wheel style because they couldn't get the magnetic circuit right with the old one. You may face the same difficulty.

If you aren't equipped to do comparative anatomy of the system with the two sensors analytically, maybe it's time to set up a test rig.



Mike Halloran
Pembroke Pines, FL, USA

 

[JonathanK]

Well a hall sensor operates close to zero movement, whereas a VR sensor requires velocity to generate a signal. The motor I have was never sequential fuel/spark controlled at idle, it was only switched over at higher RPM once the cam tooth made a good clean sweep. Because Hall uses a 0/5v square wave with sensitivty close to zero movement, the tooth and sensor are no longer an issue, just whether or not mounting the sensor in a ferrous holder, about 1/2" from the end, will hurt performance or not.

 

[MikeHalloran]

The answer to your question is, "It depends on the magnetic circuit.". I.e., the tooth and sensor, and your sensor mount, all interact magnetically, and are potentially 'issues'.

There may be a technical section in your Hall sensor catalog that explains it. Maybe you need the thicker catalog.



Mike Halloran
Pembroke Pines, FL, USA

 

[BobM3]

As Mike says, you need to look at the magnetic path. Flux density has to pass through the Hall effect device. I'd be surprised if it worked with just an aluminum housing mount. Most of the time you need iron to help direct the magnetic flux through the device. Even worse, you need a change in magnetic flux to get the device to turn on and off. Teeth from a gear passing the device might not generate enough variation in the flux density to get the device to turn on and off. Often times you need an analog output from the device with conditioning electronics to give you a square wave on/off electrical signal.