Various technologies are used to make pressure sensors. Two of the most common include piezoresistive and capacitive pressure sensors. Both can be used for gauge, differential or absolute pressure measurement. While piezoresistive is found in low-cost sensors, there are situations where a capacitive pressure sensor is better suited for the application.

In capacitive pressure sensors, the electrical capacitance changes with pressure. In simplified terms, this change in capacitance is measured and converted to a pressure measurement. This capacitive element technique creates a pressure sensor with key advantages, including:

Robustness

Capacitive pressure sensors can easily withstand high proof pressures and overpressure.

Temperature performance

These sensors can operate over a wider temperature range than traditional piezoresistive pressure sensors.

Power consumption

Capacitive pressure sensors use low power because no bias is required to operate the sensor. This feature makes the sensors suitable for industrial internet of things (IIoT) products where power use is critical. The sensors can be operated in extremely low power modes until activated when needed.

Accuracy

Low hysteresis, high repeatability and low sensitivity to temperature changes allow for highly accurate sensors.

Long-term stability

Minimal drift gives users superior long-term stability over other pressure sensors.

Newer packaging styles

Capacitive sensors have become much smaller compared to older generations that resembled a brick.

Because the production and calibration costs of capacitive sensors are higher, it is not expected to act as a replacement for lower-cost piezoresistive pressure sensors. Instead, these newer generation capacitive sensors open up opportunities for pressure measurement than cannot be done with piezoresistive pressure sensors. Some sample applications include:

Production equipment

Automated pumps and valves need to be monitored for pressure. A capacitive sensor has the safety to be exposed to harsher environments.

Industrial filter monitoring

Figure 1: Automated pumps and valves need to be monitored for pressure. Source: Servoflo

Differential pressure measurement is required to monitor filter clogging in industrial equipment. The capacitive sensor offers excellent overpressure tolerance (typically 100 times) and has a minimum in-line pressure drop requirement.

Powerless pressure monitoring system

Due to its nature, a capacitive pressure sensor does not require DC bias for its operation, minimizing power requirements and allowing the user to set up remote wireless monitoring. Wireless level tank monitoring can be done by creating a sensor network with data sent to the cloud. The excellent overpressure tolerance and high accuracy combined with the low power requirement make the capacitive pressure sensors a unique solution to solving difficult pressure measurement situations.

To learn more about the advantages of capacitive pressure sensors, check out these blog posts:

• High Accuracy Capacitive Pressure Sensors
• Learn the Differences: Rated Pressure, Overpressure, and Burst Pressure

Here are some capacitive pressure sensors offered by Servoflo:

Not sure what kind of sensor you might need? Take advantage of Servoflo’s pressure sensor selector tool, which provides customers with specific options for their applications.