Fire67

iTrader: (3)

I'm trying to use the Traction control features of my FAST XFI... This will use the stock VSS (or in my case the 454 SS Silverado speed sensor). Just need to know whether the sensor itself is an inductive, or hall effect sensor.

Anyone know? Trying to get this wrapped up ASAP!

Thanks in advance

69LT1Bird

iTrader: (1)

I believe it is pulse width modulated

Fire67

iTrader: (3)

Im retarded when it comes to this stuff. But I know the sensor puts out pulses, just need to know what kind/type of signal the sensor itself puts out.

Can the sensor itself be defined as either inductive or discrete?

Gilbert@Ace Racing

It is going to be an Inductive sensor.

FYI... PWM or Pulse Width Modulation refers to an output signal from the PCM. It is used in several different systems on the vehicle. ABS, Fuel Injectors and ATomiatic Tranny Pressure Control Solenoids are just a few examples.

Instead of a dedicated on / off signal the device is given a very rapid pulsing signal that will oscillate the device that is being driven.

g

Fire67

iTrader: (3)

Thank you very much sir!!!!!

I knew that pulse width modulation is used to control things... Which is what threw me off before. Going by 69LT1birds reply, I could only glean that the sensor itself was pulse width modulated by something else... Which didn't seem to equate with what I do know. The sensor itself generates the pulses.

Gilbert@Ace Racing

Well yeah... sort of...

In an inductive sensor setup there is an amplified magnetic field that is interrupted when, in this case, the tone wheel on the output shaft is rotated. The PCM will count these "pulses" and generate an output signal to the speedometer and make adjustments to fuel delivery and other systems according to the current pulse count. Late GM trannys use a 40 tooth reluctor wheel.

Another example of this system is the MSD Crankshaft Trigger. In this case, the magnets are mounted on the rotating wheel instead of the sensor itself. The sensor is a low voltage device and can be easily interfered with, that's why the harness is a "twisted pair" of wires. The twisting of the wires will amplify the return signal and will typically cancel any RFI.

Hope that helps take some mystery out of 'em.

g

Fire67

iTrader: (3)

That definitely helps alot. Aren't the MSD products a "discrete" pickup?

For some reason I've been thinking that the inductive vs. discrete described the signal itself. Is it actually the type of pickup?

Gilbert@Ace Racing

It is a "discrete" signal. But, in essence it is an inductive setup.

Here are some explanations from Wikipedia that helps to take the discussion a bit further....

Inductive Sensor:

is an electronic proximity sensor, which detects metallic objects without touching them.

The sensor consists of an induction loop. Electric current generates a magnetic field, which collapses generating a current that falls asymptotically toward zero from its initial level when the input electricity ceases. The inductance of the loop changes according to the material inside it and since metals are much more effective inductors than other materials the presence of metal increases the current flowing through the loop. This change can be detected by sensing circuitry, which can signal to some other device whenever metal is detected.

Hall Effect:

Automotive ignition and fuel injection

Commonly used in distributors for ignition timing (and in some types of crank and camshaft position sensors for injection pulse timing, speed sensing, etc.) the Hall effect sensor is used as a direct replacement for the mechanical breaker points used in earlier automotive applications. Its use as an ignition timing device in various distributor types is as follows. A stationary permanent magnet and semiconductor Hall effect chip are mounted next to each other separated by an air gap, forming the Hall effect sensor. A metal rotor consisting of windows and tabs is mounted to a shaft and arranged so that during shaft rotation, the windows and tabs pass though the air gap between the permanent magnet and semiconductor Hall chip. This effectively shields and exposes the Hall chip to the permanent magnet's field respective to whether a tab or window is passing though the Hall sensor. For ignition timing purposes, the metal rotor will have a number of equal-sized tabs and windows matching the number of engine cylinders. This produces a uniform square wave output since the on/off (shielding and exposure) time is equal. This signal is used by the engine computer or ECU to control ignition timing. It is worth noting that many automotive Hall effect sensors have a built-in internal NPN transistor with an open collector and grounded emitter, meaning that rather than a voltage being produced at the Hall sensor signal output wire, the transistor is turned on providing a circuit to ground though the signal output wire.

I highlighted the fundamental differences of the two sensors. Both use a magnetic field... but one uses a NPN transistor and an excited magnet whereas the other uses a winding around a ferrite metal to generate the magnetic field. Both are looking for an interruption in the magnetic field.

g

Fire67

iTrader: (3)

Wow, that makes it pretty well clear. I had initially tried Wikipedia, but I think I was using the wrong search words. Thanks again sir!