Hall effect sensors VS LVDT.

[firewalker]

A common way in automotive industry to measure absolute position is the use of Hall effect sensors. Like TPS (Throttle Positions Sensor), APP (Accelerator Pedal Position), SAS (Steering Angle Sensor) etc.

When it come to suspension systems the most common sensor is LVDT (Linear Voltage Differential Transformer).

Why? Speed? Sensitivity?


LVDT:





Alexander.

[b_force]

A LVDT is a mechanical way to measure things.
Depending on your application, that could give an extra 'load' on the part that's moving, and therefor you will get different results.
Also mechanical components in general will break or need to be replaced more often.

Besides there are also obvious reasons, like speed, acceleration etc.
That's just matter of checking the specs.

[HighVoltage]

The newest generation that we find in cars now, are Self Calibrating TPOS Speed Sensors.
They have higher accuracy and faster reaction times.

LVDT is far too slow for most applications.
Since the suspension is relative slow, it is ok to use LVDT
 

[firewalker]

What does True Power On State refers to?

Alexander.

[David Hess]

LVDTs are much more reliable than hall effect sensors and especially so under adverse conditions.  Hall effect sensors are just cheap.

[HighVoltage]

What does True Power On State refers to?

Alexander.

Here is the datasheet attached.

Features and Benefits:
- Chopper stabilized; optimized for automotive cam sensing applications
- Optimized absolute timing accuracy step size through gradual transition from TPOS to Running Mode
- High immunity to signal anomalies resulting from magnetic overshoot and peak-to-peak field variation
- Tight timing accuracy over full operating temperature range
- True zero-speed operation
- Automatic Gain Control circuitry for air gap independent switchpoints
- Operation at supply voltages down to 3.3 V
- Digital output representing target profile
- Undervoltage lockout (UVLO)
- Patented Hall IC-magnet system
- Increased output fall time for improved radiated emissions performance

[firewalker]

So, TPOS means it knows the absolute position of the object immediately after power up. Correct?

Alexander.

[HighVoltage]

Yes, and it knows in which direction the shaft is turning.
So, it is one more indication of possible backfire and a reverse running engine, to shut off all fuel supply and ignition.