Engine Speed (rpm) Sensor

[blank]

Does anyone know where to get a "magnetic" engine speed sensor? The kind sometimes used during an MOT that is just stuck on to a magnetic part of the engine and (I assume) picks up engine vibration.

Also does anyone know what type of electrical signal they give out?

This is to record engine speed on cars where fitting an optical tacho isn't possible, and they don't have CANBUS/OBD.


Thanks

[blank]

Mr2Mike said:

I suspect OP is getting confused with inductive pickup tachometers that clip onto an HT lead.

Similar idea, yes. But obviously modern cars (and diesels) don't have HT leads.

http://www.premierdiagnostics.ltd.uk/elitecombi.ht...

This system seems to have the type of sensor, so I'll speak to them and try to get just the sensor but I assumed they were quite common in the world of MOTs.

The end goal is to get an electrical signal (analogue, TTL, whatever) of engine RPM using something that is quick/easy to fit, and works on most engines.


To the person who asked about an optical tacho...

You put some reflective tape on the crank pulley, and mount an optical sensor nearby. This picks up the tape every revolution of the engine and sends out an electrical pulse. Works but is obviously time consuming to fit and set up.

[blank]

GreenV8S said:

Petrol and / or diesel?
Temporary use or permanent fitment?
While stationary or while driving?

Petrol and diesel.

Temporary use. Minimum couple of hours, maximum couple of weeks.

While stationary and while driving.


I have one of these on the way to try:
http://www.kmt-telemetry.com/sensorless-speed-rpm-...

This uses battery voltage ripple so we will see how it gets on.


This is (in theory) ideal but I can't seem to find a European equivalent:

http://pdf.directindustry.com/pdf/wuhan-cubic-opto...

[blank]

It is for various forms of vehicle testing where we want to record engine speed along side various other sensors.


Regarding OBD...

As in first post, OBD is usually option 1 but this is for vehicles without OBD functionality.

[blank]

PaulKemp said:

You can get a tacho feed from the coilpack using zener diodes, a simple diy home electrics project, this measures the ecu pulses to trigger the coil so not a direct measurement.

If the engine is a modern one then it already has a VR sensor triggered by a trigger wheel

Difficult to advise on this thread without more details

We did try this but it was a bit noisy. Also tapped in to the cam position sensor which seemed to work reasonably well.

Crank sensor was unfortunately inaccessible.


Anyway the "battery ripple" box seems to work.


Still intrigued by the magnet/microphone sensors though. If I can get hold of one to try then I will.

[blank]

stevieturbo said:

Except that it very much matters.

Is it just something to view, log, what type of signal, self powered, etc etc etc ?

It is to log alongside various other signals. TTL or analogue signal would be ideal (I said this further up).

Power doesn't really matter either way.