Speedo sensor again!!!

timeandtide · May 13, 2021

I’m fairly sure my third has just given up the ghost and the bike, a twin cam is under 60K miles!
Loathe to fork out £94 for another new one - any bright suggestions for a work around?
Best I can come up with is a s/h one from Motorworks @ about half price.
Strangely never had a problem with either of my other two 1200s.

DrFarkoff · May 13, 2021

timeandtide said:
I’m fairly sure my third has just given up the ghost and the bike, a twin cam is under 60K miles!
Loathe to fork out £94 for another new one - any bright suggestions for a work around?

Get a BM dealer to fit one and you get 2 year warranty on fitted parts

In reality It would be a much better idea to find out "WHY?"

Is it a Damaged / nipped cable, cable too short, water ingress to the connection or just a failed sensor

If it's a failed sensor and you have a record of Purchasing and fitting them?

I would think there is quite possibly an issue with cabling or routing??

StewMcGrew · May 13, 2021

Have you taken it out and cleaned the metal filings off it? The sensor is magnetic and these filings can interfere with the reading.

timeandtide · May 13, 2021

Bike brought from Rainbow a year old - they fitted one, or possibly two, third bought from Pidcocks and fitted by Mikeyboy so no problems with fitting, fit etc - thanks for your thoughts.

timeandtide · May 13, 2021

Will check this out thanks.

AustinW · May 13, 2021

On my 2011 GSA I got through two rear speedo sensors. I then had the FD rebuilt by Mikeyboy at about 50k miles, partly as a precaution partly out of need (oil leaking out, water leaking in). After the rebuild and reuse of the old sensor I had no further problems with speed sensor for the next 30,000 miles I kept the bike for.

So either I was doing something weird fitting them (doubt it as it’s not hard) or there is something that goes slightly amiss inside the FD that causes problems over time - which could be metal bits but could be something ever so slightly out of alignment.

Mistacat · May 13, 2021

Someone with a greater knowledge of these 2 wire sensors will be along soon.
I have tested car 2 wire sensors with an oscilloscope, they put out an AC waveform , I have not recorded the amplitude, just compared wave forms.
I would imagine that the output from these sensors could be measured with a multimeter on a low AC voltage range with the bike running in gear and rear wheel off the ground.
The sensors tend to be reliable so, as previously mentioned check that it is clean and also that all of the connectors are good.
When I get around to it I will mount an ABS ring in the lathe chuck and a sensor on the tool post then hook it up to the scope, for my own interest.

Mistacat · May 13, 2021

AustinW said:
On my 2011 GSA I got through two rear speedo sensors. I then had the FD rebuilt by Mikeyboy at about 50k miles, partly as a precaution partly out of need (oil leaking out, water leaking in). After the rebuild and reuse of the old sensor I had no further problems with speed sensor for the next 30,000 miles I kept the bike for.

So either I was doing something weird fitting them (doubt it as it’s not hard) or there is something that goes slightly amiss inside the FD that causes problems over time - which could be metal bits but could be something ever so slightly out of alignment.

I would agree that if there is play in the FD then the sensor to crown wheel clearance could be compromised, ( the ABS ring is machined into the back of the crown wheel.

timeandtide · May 13, 2021

Thanks for your helpful comments gents.
Mine’s also a 2011 bike which has had a final drive rebuild by Mikeyboy.
No ABS.
I understood that the (Hall?) sensors were pretty reliable although I know nothing about electrickery!

johnnyboy · May 13, 2021

If you can see a part number on the sensor, do a Google search. There will be companies out there that sell them. I did similar for a tyre pressure sensor on my superduke, it was half the price that ktm wanted.

Sent from my SM-G970F using Tapatalk

Mistacat · May 13, 2021

timeandtide said:
Thanks for your helpful comments gents.
Mine’s also a 2011 bike which has had a final drive rebuild by Mikeyboy.
No ABS.
I understood that the (Hall?) sensors were pretty reliable although I know nothing about electrickery!

The ABS and non ABS bikes both use the same sensor and Sensor / ABS ring which are actualy grooves machined into the back of the crown wheel.

timeandtide · May 13, 2021

johnnyboy said:
If you can see a part number on the sensor, do a Google search. There will be companies out there that sell them. I did similar for a tyre pressure sensor on my superduke, it was half the price that ktm wanted.

Sent from my SM-G970F using Tapatalk

Tried that but no joy unfortunately!
Thanks for the suggestion.

Santa-2512 · May 13, 2021

Mistacat said:
Someone with a greater knowledge of these 2 wire sensors will be along soon.
I have tested car 2 wire sensors with an oscilloscope, they put out an AC waveform , I have not recorded the amplitude, just compared wave forms.
I would imagine that the output from these sensors could be measured with a multimeter on a low AC voltage range with the bike running in gear and rear wheel off the ground.
The sensors tend to be reliable so, as previously mentioned check that it is clean and also that all of the connectors are good.
When I get around to it I will mount an ABS ring in the lathe chuck and a sensor on the tool post then hook it up to the scope, for my own interest.

Sensor is a misnomer,

It senses nothing so to speak, it is a hall effect sensor

Basically it is a coil wrapped around a magnet, when energised it develops a magnetic field,

As the reluctor ring passes through the field, it disrupts it, and causes a pulse as you said, a square wave if i recall

The abs unit reads these pulses, and works out the wheels are turning.

what goes wrong

The magnet fails and the magnetic field diminishes, and the pulses cant be generated as the field disruption is minimised

Generally they last for ages, but heat can kill them, i had two go on a car engine.

My guess is a broken wire in the coil, or a dry joint. unfortunately neither are repairable.

if the op can find another sensor that fits has the same operating parameters, he may find a cheaper supplier

timeandtide · May 13, 2021

Santa-2512 said:
Sensor is a misnomer,

It senses nothing so to speak, it is a hall effect sensor

Basically it is a coil wrapped around a magnet, when energised it develops a magnetic field,

As the reluctor ring passes through the field, it disrupts it, and causes a pulse as you said, a square wave if i recall

The abs unit reads these pulses, and works out the wheels are turning.

what goes wrong

The magnet fails and the magnetic field diminishes, and the pulses cant be generated as the field disruption is minimised

Generally they last for ages, but heat can kill them, i had two go on a car engine.

My guess is a broken wire in the coil, or a dry joint. unfortunately neither are repairable.

if the op can find another sensor that fits has the same operating parameters, he may find a cheaper supplier

Thanks for the explanation -part has BMW stamped on it so I don’t hold out any great hope of finding one!

Mistacat · May 15, 2021

Santa-2512 said:
Sensor is a misnomer,

It senses nothing so to speak, it is a hall effect sensor

Basically it is a coil wrapped around a magnet, when energised it develops a magnetic field,

As the reluctor ring passes through the field, it disrupts it, and causes a pulse as you said, a square wave if i recall

The abs unit reads these pulses, and works out the wheels are turning.

what goes wrong

The magnet fails and the magnetic field diminishes, and the pulses cant be generated as the field disruption is minimised

Generally they last for ages, but heat can kill them, i had two go on a car engine.

My guess is a broken wire in the coil, or a dry joint. unfortunately neither are repairable.

if the op can find another sensor that fits has the same operating parameters, he may find a cheaper supplier

Excellent, someone who knows about these "sensors" I still call them sensors as I was under the impression that they sensed a change in magnetic field.
The questions,
Are these Active or Passive sensors?
I had assumed they were passive ( Analogue) as they are 2 wire hence the reference to a sine wave .
If Active do they use the mounting screw for ground as some do? I had discounted this ( probably incorrectly) in this application as the earth path is through bearings.
I appreciate Active sensors have a digital output having an IC to convert the sine wave to a square wave.
I know that they are both Hall effect sensors and more likely to be Active but but the 2 wire threw me, Normally I would expect 3 connections, Reference voltage, Signal, Ground.
I will put off testing one until I get this information.

Santa-2512 · May 15, 2021

Mistacat said:
Excellent, someone who knows about these "sensors" I still call them sensors as I was under the impression that they sensed a change in magnetic field.
The questions,
Are these Active or Passive sensors?
I had assumed they were passive ( Analogue) as they are 2 wire hence the reference to a sine wave .
If Active do they use the mounting screw for ground as some do? I had discounted this ( probably incorrectly) in this application as the earth path is through bearings.
I appreciate Active sensors have a digital output having an IC to convert the sine wave to a square wave.
I know that they are both Hall effect sensors and more likely to be Active but but the 2 wire threw me, Normally I would expect 3 connections, Reference voltage, Signal, Ground.
I will put off testing one until I get this information.

I'm no expert,

But been around various sensors and components in the day job, to give me a working understanding

ABS sensor is an easier way to say magnetic field effect sensor

if you think about it, you cant sense abs

all it does is convert magnetic field variations into a pulse - - - - - - - - - but displayed as a sine wave /\/\/\/\/\/\/\/\/\/\/\

when the field gets disrupted by a wheel locking up \/\/\/\/ --- \/\/\/\/\/ ---- \/\/\/\/\/ -- \/\/\/ it's the ABS ECU that reads that string of pulses , and reacts, triggering the release of brake

pressure at the ABS module

Active / passive is a trickier one.

They are active in the sense that they generate a signal from the disruption of the magnetic field

see the pictures below ,

they give a basic overview of how they work

they can be used in many applications ,

camshaft or crank sensor, ( the lobe passing past the magnet will generate a pulse and can be used to work out TDC & BDC)

Ive seen them used to do ignition timing applications as well

If you look at the smaller unit, it's closest to what's in the bike, i'm pretty sure its just a metal sleeve to stop the part being snapped when fitted

Two things i do know,

Sometimes unplugging and plugging them in again can cause enough voltage change to generate enough magnetic field for them to work, (but it's short lived )

Air gap is critical, to close and you run the risk of damaging the reluctor ring or the sensor itself.

too far away from the sensor and it wont disrupt the field enough

BTW the pics are generic and not related to the bm unit at all
HTH

Edit,

if you feel adventurous you could always have a play around

https://www.euspares.co.uk/parts/ridex/8058786

Shows an abs sensor, they are dirt cheap !

If you could find on in the same package size as the BM one, nothing to stop you could makeing an adpator cable

and see if it works

Heres a bm one with a cable on it

https://www.euspares.co.uk/parts/abs/7713410

food for thought?

UturnTony · May 15, 2021

Santa-2512 said:
Sensor is a misnomer,

It senses nothing so to speak, it is a hall effect sensor

Basically it is a coil wrapped around a magnet, when energised it develops a magnetic field,

As the reluctor ring passes through the field, it disrupts it, and causes a pulse as you said, a square wave if i recall

The abs unit reads these pulses, and works out the wheels are turning.

what goes wrong

The magnet fails and the magnetic field diminishes, and the pulses cant be generated as the field disruption is minimised

Generally they last for ages, but heat can kill them, i had two go on a car engine.

My guess is a broken wire in the coil, or a dry joint. unfortunately neither are repairable.

if the op can find another sensor that fits has the same operating parameters, he may find a cheaper supplier

....

Mistacat · May 15, 2021

Both Active and passive sensors generate a signal through the disruption of the magnetic field.
Figure 1 is an active sensor with the ground through the mounting screw.
Figure 2 to the right of figure 1 is a passive analogue sensor output is a sine wave.
Fig 3 The Reluctance sensor is passive.
Fig 4 The Magnetoresistive sensor is one of the types of Active sensor showing the IC that converts the sine wave to square wave.
This does not answer the question as to which type the R1200 uses.
Guesswork would suggest it would need to be active as the data set would be more viable for the traction control but the wiring ??.
Perhaps if someone has a dead one they could dissect it and see if there is a connection to the mounting bush or is it just there to reinforce the plastic.

Santa-2512 · May 15, 2021

UturnTony said:
....

Yes i know lol

but how do you sense abs

ifs a field effect sensor

Mistacat · May 15, 2021

Decided as it is raining to do a couple of tests.
First, the BMW ABS sensor is an active sensor.
The impedance measured across the 2 pins is 14.7 Meg ohm's.
There is a reference voltage which is battery voltage with ignition on and charging voltage with engine running this can be measured from the ECU.
The signal waveform measures approx. 0.5 volts peak to peak this is on the reference voltage.
Here are three pictures,
The first is the scope hook up to the ABS sensor connector.
The second is the DC reference voltage with the signal ripple on it ( 2nd gear engine at idle).
The 3rd showing the actual signal waveform ( 2nd gear engine at idle)

[/IMG]

Speedo sensor again!!!

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