Stock manual transmission vehicle speed sensor waveforms (Page 1/1)
pmbrunelle SEP 29, 07:59 PM
This thread is just to record information about the Fiero VSS that I measured; I do not require any specific assistance. Maybe this will be useful to someone.

I spun the VSS in a drill, and I captured some voltage waveforms with an oscilloscope.

In the bottom-right area of the oscilloscope screen, I had the oscilloscope display the peak-to-peak voltage as well as the frequency:









Here is the DC resistance:
Raydar SEP 29, 09:43 PM
Obviously the frequency increases with speed. I'm surprised to see the amplitude do the same thing.
pmbrunelle SEP 29, 11:35 PM
I think it's a permanent magnet spinning and inducing voltage in the coil, so it would make sense for the amplitude to go up with speed.

code:

Voltage    Freq          Ratio
3.0 V      4.8100 Hz     0.623 V/Hz
12.1 V     19.806 Hz     0.611 V/Hz
46.6 V     87.205 Hz     0.534 V/Hz
68.3 V     137.80 Hz     0.496 V/Hz


The amplitude is sort of linear with speed, but I guess it would change with the temperature of the permanent magnet.

The fastest speed I tested was as fast as the drill would go.

The slowest speed corresponds with creeping along in 1st gear at the engine's idle speed. It is close to the lowest speed which needs to be reliably detected by the ECM.

People refer to this VSS as being "sine wave", so I was expecting more of a sine wave rather than a sine deformed into a triangular shape.