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In the article “Low-pressure sensors driven by a constant-current source” I introduced the basic parameters of pressure sensors. In this instalment I’ll continue with a brief introduction to several common parameters of pressure sensors, because understanding these parameters helps us precisely choose sensors that meet a project’s design requirements.
1. Medium compatibility
Medium compatibility refers to the medium that comes into direct contact with the sensor’s sensing area — usually a liquid or a gas. Pressure sensors are typically compatible with dry, non-corrosive gases. The important point is that the medium must not corrode the sensing diaphragm or the chip housing, because corrosion will cause reliability issues. The medium compatibility can vary from one model to another. For harsher environments — for example, gases that may be corrosive — products with a metallised sensing diaphragm are usually chosen.
2. Rated pressure range
The rated pressure range is the maximum pressure value defined in the sensor’s specifications; the rated pressure guarantees normal operation of the pressure sensor. This pressure value defines the sensor’s full-scale output. Within this range the specification-defined parameters are assured. Note that different sensors may be calibrated and specified in different units — pressure sensors are commonly calibrated in hPa, kPa, bar or psi.
3. Proof/withstand pressure
Proof (withstand) pressure is the maximum pressure that may be applied without causing damage to the sensor chip’s performance. This should not be used as a routine operating pressure — at this pressure the output may already be saturated.
4. Burst pressure
Burst pressure is the maximum pressure that can be applied without causing permanent damage to the sensor chip; this also should not be used as a normal operating pressure. After experiencing such a pressure, the sensor’s performance may need to be re-evaluated.
5. Compensated temperature range
The compensated temperature range is the temperature range within which the sensor’s specified parameters are guaranteed. In practice this means temperature drift has been compensated for. This range is closely related to the user’s application temperature range. For example, if you need the sensor to still meet its datasheet accuracy at 50°C, you must choose a product whose compensated temperature range extends above 50°C. On the market, pressure sensors typically have wide temperature compensation ranges, often set from −10°C to 60°C.
6. Zero-point drift
Zero-point drift refers to the sensor’s output when no pressure is applied. It is usually expressed as a percentage of full scale, or in mV, mA or digital bits. This drift is easy to remove during calibration, so when replacing sensors it’s important to perform a zero-point drift calibration.
7. Linearity
Linearity is a very important concept. Ideally, a pressure sensor’s output would be a perfect straight-line relationship with the applied pressure. In real applications there will be some non-linear behaviour — the deviation between the actual output and the ideal straight line. Non-linearity is the parameter used to describe that deviation, and it’s usually calculated using the best-fit straight-line method. It is one of the key contributors to measurement error in pressure sensors.
Conclusion
Medium compatibility: Ensure the sensing diaphragm and housing resist the specific gas or liquid to avoid corrosion and reliability issues.
Rated pressure range: Defines the sensor’s full-scale output and where datasheet specs are valid.
Proof/withstand pressure: Maximum pressure allowed without performance damage — not for normal operation.
Burst pressure: The absolute maximum before permanent damage risk; any exposure requires re-evaluation.
Compensated temperature range: Temperature band over which accuracy is guaranteed after temperature compensation — choose one covering your maximum operating temperature.
Zero-point drift: Output with no pressure applied; usually corrected during calibration — re-calibrate when replacing sensors.
Linearity: Deviation from an ideal straight-line response; key contributor to measurement error and usually expressed vs best-fit straight line.
The above introduction only scratches the surface of the applications of pressure sensor technology. We will continue to explore the different types of sensor elements used in various products, how they work, and their advantages and disadvantages. If you’d like more detail on what’s discussed here, you can check out the related content later in this guide. If you are pressed for time, you can also click here to download the details of this guides air pressure sensor product PDF data.
For more information on other sensor technologies, please visit our sensors page.
