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Pressure Sensors tutorial

Modules

1. Introduction to Pressure Measurement
2. Piezoresistive Pressure Sensor
3. Capacitive Pressure Sensor

pages: [1] 2 3 | next

Basic arrangement of a pressure sensor

Differential pressure measurement - between input1 and input2,

Gauge pressure measurement - if the input2 is closed under the atmospheric pressure conditions,

Absolute pressure measurement - when the input2 is vacuum sealed.

Sensor fundamental part - plate (membrane) of silicon or polysilicon equipped with one or several piezoresistives gauges.

The pressure difference induces a stress variation in the plate.

The resulting stress is then measured by piezoresistive gauges that are placed in specific places of a plate.

Piezoresistors can be diffused in silicon plates with different crystal orientations, along many crystal directions.

In order to make an optimal choice of a piezoresistive sensor location, the stress pattern on the surface of the plate deformed by the pressure difference should be known.

Typical geometrical forms of the sensor membrane

      • Circular form
        The simplest in terms of stress estimation,
        Symmetrical and easy to analyse,
        Difficult to obtain in (100) planes by micromachining.
      • Square form is more easy to obtain by micromachining
        Behaves similarly to a circular plate in the centre, but at the edges, the stress is more concentrated towards their centers.
        This fact may have as a consequence ruptures of square plates in lower pressure differences.
      • Ring form
        Obtained if the centre part of a plate is not etched,
        Can be considered for certain applications where only small pressure differences have to be measured,
        Better nonlinear behaviour.

1. Introduction to Pressure Measurement
2. Piezoresistive Pressure Sensor
3. Capacitive Pressure Sensor

pages: [1] 2 3 | next

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