Engine Speed (rpm) Sensor
Discussion
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
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 said:
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.
Never heard of anyone sticking a rev counter on a car for an MOT.blank said:
This is to record engine speed on cars where fitting an optical tacho isn't possible
Optical tacho? What is one of them?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 said:
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.
OK, I stand corrected, still never seen one before though.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.
blank said:
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.
Now that sounds like a big job for an easy solution.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.
What about just plugging an OBD reader into the car & viewing live data stream for the engine revs, or is it for a permanent gauge?
blank said:
Similar idea, yes. But obviously modern cars (and diesels) don't have HT leads.
You can get eprobes for diagnosing COP ignition systems, which sit on top of the coil. Probably not as suitable for semi-permanent installation though which it sounds like you need?E-bmw said:
OK, I stand corrected, still never seen one before though.
Me either. Guessing it's effectively a microphone built like a wideband knock sensor, e.g. piezo element and a weight. There would need to be a DSP at the other end to resolve the required frequency components. I have to wonder how reliable this is though given the vast number of different frequency components that an engine produces, whose relative levels can change with RPM and throttle opening.Edited by Mr2Mike on Monday 22 May 14:13
GreenV8S said:
Petrol and / or diesel?
Temporary use or permanent fitment?
While stationary or while driving?
Petrol and diesel.Temporary use or permanent fitment?
While stationary or while driving?
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...
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
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
stevieturbo said:
GreenV8S said:
I'm intrigued - what do you want the rpm signal for?
I did ask days ago and got no specific answer.blank said:
It is for various forms of vehicle testing where we want to record engine speed along side various other sensors.
Don't be so nosey 
Sometimes when you pose a question you can be intelligent enough to know that any more information is not needed and would derail the topic from the specific point needed, or it could be that you don't want the whole World to know all of your private or personal business.
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.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
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.
227bhp said:
Don't be so nosey
Sometimes when you pose a question you can be intelligent enough to know that any more information is not needed and would derail the topic from the specific point needed, or it could be that you don't want the whole World to know all of your private or personal business.
Except that it very much matters.Sometimes when you pose a question you can be intelligent enough to know that any more information is not needed and would derail the topic from the specific point needed, or it could be that you don't want the whole World to know all of your private or personal business.
Is it just something to view, log, what type of signal, self powered, etc etc etc ?
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