Pressure Sensors Demystified: Data, Accuracy & Care

Pressure Sensors Demystified: Data, Accuracy & Care

Pressure sensors are the unsung heroes in countless applications, from monitoring industrial processes and medical devices to ensuring your car's engine runs smoothly. But how much do you really know about these vital components? Let's dive into three fundamental questions.

1. What Data Does a Pressure Sensor Collect?

At its core, a pressure sensor collects one primary piece of information: force per unit area applied to it by a fluid (gas or liquid). This is the definition of pressure itself.

• The Raw Measurement: The sensor physically deforms (often a diaphragm) under pressure. This deformation is converted into an electrical signal (like voltage, current, or a digital value) proportional to the applied pressure.

• Units Matter: The collected data is expressed in units like:

  • Pounds per Square Inch (psi)

  • Bar or millibar (mbar)

  • Pascals (Pa) or kilopascals (kPa)

  • Inches or Millimeters of Water Column (inH₂O, mmH₂O)

  • Atmospheres (atm)

  • Torr or mmHg (common in vacuum/medical)

• Type Dictates Meaning: The interpretation of the data depends on the sensor type:

  • Absolute Pressure Sensors: Measure pressure relative to a perfect vacuum. (e.g., barometric pressure, altimeters).

  • Gauge Pressure Sensors: Measure pressure relative to the local atmospheric pressure. (e.g., tire pressure, blood pressure - cuff pressure).

  • Differential Pressure Sensors: Measure the difference in pressure between two points. (e.g., filter monitoring, flow measurement).

  • Sealed Gauge Pressure Sensors: Measure pressure relative to a fixed, sealed reference pressure (not ambient atmosphere).

In essence, the sensor outputs an electrical signal that reliably represents the magnitude of the pressure force acting upon it, interpreted based on its type and calibrated units.

2. How Accurate Are Pressure Sensors?

Pressure sensor accuracy is highly variable and depends on numerous factors. There's no single answer, but here's a breakdown:

• Accuracy Ranges: Accuracy is typically specified as a percentage of the sensor's Full Scale (FS) range or sometimes as a percentage of the reading (% RD). Common ranges include:

  • High Precision: ±0.05% FS to ±0.1% FS (Used in critical labs, calibration standards).

  • Very Good: ±0.25% FS to ±0.5% FS (Common in demanding industrial/process control).

  • Standard/Good: ±1.0% FS (Widely used in industrial automation, HVAC, many OEM applications).

  • Lower Cost/Less Critical: ±2% FS or higher (Suitable for some consumer goods, basic indication).

• Key Factors Influencing Accuracy:

  • Sensor Technology: Strain gauge, capacitive, piezoelectric, MEMS, optical – each has inherent accuracy limits and characteristics.

  • Calibration: Factory calibration against traceable standards is crucial. Accuracy specs assume proper calibration.

  • Temperature Effects: Temperature changes cause significant drift. Accuracy specs often include TEB (Total Error Band), which combines initial accuracy, non-linearity, hysteresis, and temperature effects over a specified range. A sensor with ±0.5% FS accuracy might have a TEB of ±2.0% FS over 0-70°C.

  • Hysteresis: Does the sensor give the same reading when pressure is increasing vs. decreasing?

  • Non-Linearity: How much does the output deviate from a perfectly straight line between zero and full scale?

  • Long-Term Stability (Drift):&nb