Axle rotation speed sensor

[Jean-Marc]

My engine is now running, and I am in the process to adjust the cables of the gear box. But when the wheels are spining I have no speed displayed on the gauge. The sensor is close to the right axle of the gear box.
Does anybody knows how its work?
Does a magnet is require, or does he is activated by the head of the screw (change of magnetic field)?
If it is the screws that activate it what gap shall I put between sensor and screws ?
How to test it.
Does the wire (2 wires) are polarized
Who is the manufacturer

 

[Neal]

These are usually Hall Effect sensors. They generate a pulse output which changes frequency as speed increases. Some trigger with a steel target, others a magnetic target. I suspect yours triggers on the bolts.

Here is a good article describing their behavior.. https://sensorso.com/resources/selection-or-design-of-sensor-targets.html

Do a search on testing Hall effect sensors and you’ll get a ton of methods to validate operation

 

[Walter]

My RCR came with the same sensor, I believe, and it was located near the rhs rear brake rotor into which a small hole had been drilled. It did not work. You can test the sensor itself by measuring the induced voltage when swiftly moving it past an iron bolt (or tip). Finally, I did get a signal from mine. However, I could not get it to work with the gauge - I think the pin hole in the disk gave too small a pulse. Also, the sensor must be very close (~ 2mm) to the disk, which under braking, will get quite hot. Not good for any electronic device! So I ended up putting the sensor to the bolts of the axle at the transmission. In fact, I now use a different sensor "Smiths Speedo Sensor For Smiths Electronic Speedometers Inductive / Hall Effect" which has a diode blinking when in operation. It has 3 wires but is easy to wire with the RCR Classic speedo (I used an unused hot wire behind the fire wall where the shift rod passes - if I remember correctly).

 

[JP Verweij]

I discarded that system and went for a Smiths GPS sensor which was plug & play to my Smiths electric gauge.

 

[Walter]

My RCR came with the same sensor, I believe, and it was located near the rhs rear brake rotor into which a small hole had been drilled. It did not work. You can test the sensor itself by measuring the induced voltage when swiftly moving it past an iron bolt (or tip). Finally, I did get a signal from mine. However, I could not get it to work with the gauge - I think the pin hole in the disk gave too small a pulse. Also, the sensor must be very close (~ 2mm) to the disk, which under braking, will get quite hot. Not good for any electronic device! So I ended up putting the sensor to the bolts of the axle at the transmission. In fact, I now use a different sensor "Smiths Speedo Sensor For Smiths Electronic Speedometers Inductive / Hall Effect" which has a diode blinking when in operation. It has 3 wires but is easy to wire with the RCR Classic speedo (I used an unused hot wire behind the fire wall where the shift rod passes - if I remember correctly).

 

[Jean-Marc]

Neal, Walter, JP, thank you for your help, I will check this.

 

[Tom]

I mounted mine on a bracket facing the backside of the RF wheel hub/brake rotor assembly. Worked great and very accurate once calibrated. Wire run to the gauge is much shorter. Gap is set to about the thickness of a dime ~0.10".