frequently asked questions (FAQ)

Question: What is a pressure sensor?

Answer: Pressure sensors are measuring devices which convert a physical quantity (pressure) into an electrical signal according to a selected measurement method. The respective applications and accordingly also the requirements for the pressure sensor vary: Size of the sensor, installation conditions, application-specific standards, technical requirements and the properties of the medium must be taken into account when choosing the pressure sensor.

Pressure sensors are used to monitor and control processes in applications ranging from medical technology to industrial technology.

Question: What is an absolute pressure sensor?

Answer: Absolute pressure sensors are used to measure pressure against a referential pressure of 0 bar (vacuum). This enables the pressure in an enclosed system to be determined regardless of the atmospheric pressure, for example.

The whitepaper “How to measure absolute pressure using piezoresistive sensing elements” explains the basics of absolute pressure measuring.

Question: How is the fill level in liquids measured by pressure sensors?

Answer: In level sensing the fill level or height of a liquid is measured in a container. The application note “Precise level sensing with a low pressure transmitter” describes how the hydrostatic pressure can be measured using a pressure sensor.

Question: What is a relative pressure sensor?

Answer: Relative pressure sensors are used to compare a pressure with the ambient pressure, producing a signal which is proportional to the difference in pressure.

Question: What is a ratiometric sensor?

Answer: A ratiometric sensor is a sensor whose output signal reacts synchronously to changes in the supply voltage. Find more information about ratiometric sensors in application note “Ratiometry in pressure sensors” on the example of AMS 5812.

Question: How is altitude measured by an absolute pressure sensor?

Answer: The geographical altitude can be calculated by taking the atmospheric pressure and applying this to the barometric formula. The atmospheric pressure can be easily determined by an absolute pressure sensor which is calibrated to the barometric pressure range. To define the altitude the atmospheric pressure is measured at the starting point and the measurement position. The difference in pressure is entered in the barometric formula which then gives the difference in altitude between the initial position and point of measurement. Find more information in application note “Precise altitude measurement with pressure sensors” on the example of the absolute pressure sensor MS5611.

Question: What is system pressure?

Answer: The ambient pressure the system is subjected to. If, for example, a filter is to be monitored by a differential pressure sensor in the millibar range yet the static pressure in the pipe housing the sensor has already reached 10 bar, a sensor or transmitter is needed which can withstand the high pressure of the ambient air. The system pressure is the maximum pressure which can be simultaneously applied at both pressure inputs of a pressure sensor versus the external pressure without the sensor being damaged. For more information, see:

Application note “Differential pressure transmitters for high system pressures”

Question: What is a transmitter / transducer?

Answer: Transmitters or transducers are calibrated, amplified, ready-to-use sensors with a standardized output in a package for direct installation. They are also simply known as ready-to-use sensors as they do not need to be soldered or assembled before being inserted in a system. These sensors are powered by a cable and short circuit protected.

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