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Electronic pressure switches
G 1/4 M | M5 F
0 bar ... 10 bar
2x switching output
 
120.24 *
113.63

Online -5.50%

G 1/4 M | M5 F
0 bar ... 25 bar
2x switching output
 
120.24 *
113.63

Online -5.50%

G 1/4 M | M5 F
0 bar ... 100 bar
2x switching output
 
120.24 *
113.63

Online -5.50%

G 1/4 M | M5 F
0 bar ... 250 bar
2x switching output
 
120.24 *
113.63

Online -5.50%

G 1/4 M | M5 F
0 bar ... 400 bar
2x switching output
 
120.25 *
113.64

Online -5.50%

G 1/4 F
-1 bar ... 10 bar
Programmable
 
224.44 *
212.10

Online -5.50%

G 1/4 F
0 bar ... 25 bar
Programmable
 
224.44 *
212.10

Online -5.50%

G 1/4 F
0 bar ... 100 bar
Programmable
 
224.44 *
212.10

Online -5.50%

G 1/4 F
0 bar ... 250 bar
Programmable
 
224.44 *
212.10

Online -5.50%

G 1/4 F
0 bar ... 400 bar
Programmable
 
224.46 *
212.11

Online -5.50%

G 1/4 F
-1 bar ... 1 bar
Programmable
 
222.80 *
210.55

Online -5.50%

Electronic pressure sensors
G 1/4 F
-1 bar ... 10 bar
Programmable
 
270.30 *
255.43

Online -5.50%

G 1/4 F
-1 bar ... 25 bar
Programmable
 
270.30 *
255.43

Online -5.50%

G 1/4 F
0 bar ... 100 bar
Programmable
 
270.30 *
255.43

Online -5.50%

G 1/4 F
0 bar ... 250 bar
Programmable
 
270.30 *
255.43

Online -5.50%

G 1/4 F
0 bar ... 400 bar
Programmable
 
270.29 *
255.42

Online -5.50%

G 1/4 F
-1 bar ... 1 bar
Programmable
 
270.91 *
256.01

Online -5.50%

Electronic pressure transmitters
G 1/4 M
0 bar ... 10 bar
Analogue output
 
79.34 *
74.98

Online -5.50%

G 1/4 M
0 bar ... 25 bar
Analogue output
 
79.34 *
74.98

Online -5.50%

G 1/4 M
0 bar ... 100 bar
Analogue output
 
79.34 *
74.98

Online -5.50%

G 1/4 M
0 bar ... 250 bar
Analogue output
 
79.34 *
74.98

Online -5.50%

G 1/4 M
0 bar ... 400 bar
Analogue output
 
79.30 *
74.94

Online -5.50%

G 1/4 M | M5 F
-1 bar ... 1 bar
Analogue output
 
163.93 *
154.91

Online -5.50%

All about pressure sensors

What is a pressure sensor? What are the properties, advantages and disadvantages? How does the pressure measurement work and which measuring principles are there? Where are pressure sensors used? Please find answers to these questions in the following text including a conversion table for pressure units.

What does the measured variable pressure stand for and which types of pressure are there?

Pressure is a physical measured variable. It describes the force in Newton acting vertically on a surface area of a square metre (p=FN*A). The SI unit for pressure is Pascal. In industrial applications the unit bar is more common, with: 1 bar = 100,000 Pascal. A table for conversion of pressure units is given below.

Pressure data always refer to a reference value. The measured pressure corresponds to the difference between the measurement result and the reference pressure. There are the following three types of pressure data: Absolute, relative and differential pressure.
 

Differential pressure, absolute pressure or relative pressure?

Differential pressure, absolute pressure or relative pressure?
Relative pressure sketch

Relative pressure

Relative pressure specifies the pressure measured as a function of the actually present ambient pressure. The atmospheric pressure on earth is 1.013 bar. This pressure results from the weight of the air masses pressing on the earth's surface. The atmospheric pressure varies as a function of the height above sea level and therefore pressure equalisation is required when measuring the relative pressure.

Differential pressure sketch

Differential pressure

Differential pressure describes the ratio of two different system pressures, for example the difference of two pressure vessels.

Absolute pressure sketch

Absolute pressure

Absolute pressure specifies the pressure relative to an ideal vacuum, i.e. a space void of air with the pressure zero bar.

 

What are pressure sensors and what are they used for?

A pressure sensor - also referred to as pressure transducer - measures the physical process variable pressure and converts it into an electric signal which is further processed. Pressure sensors from autosen measure the relative pressure and are distinguished as electronic pressure sensors, electronic pressure transmitters and electronic pressure switches.
 

Electronic pressure sensors

Pressure sensors from autosen measure the pressure and output it as a 4 … 20 mA analogue signal. In addition they have two switching outputs issuing a binary switching signal as NO or NC contacts if defined limit values are exceeded or fallen below. They have a display of indication of the measured values and for parameterisation. We offer sensors with IO-Link for pressure ranges from -1 to 400 bar.

Electronic pressure switches

Pressure switches are suitable for limit value monitoring of system pressures. They issue a binary switching signal if a defined system pressure is exceeded or fallen below. This is to ensure that critical system pressures are in the valid range any time. Pressure switches from autosen have two antivalent switching outputs for measuring ranges from 0 … 400 bar.

Electronic pressure transmitters

Electronic pressure transmitters output the measured pressure as a continuous signal. They measure the physical process variable and convert it into an analogue standard signal. You will find pressure transmitters from autosen with analogue output 4 … 20 mA for measuring ranges from 0 … 400 bar.

 

Pressure sensor design

The design of pressure sensors is the same for each measuring principle. The sensor is installed with a process connection such that the medium gets into contact with the measuring cell and the process pressure acts on the measuring cell. The measuring cell converts the pressure into an electric variable which is converted into a standard signal in the integrated evaluation electronics. The sensor outputs the measured value via the electric connection via which it is also supplied with the required operating voltage.
 

How does a pressure sensor work?

Pressure sensors use different functional principles for pressure measurement. Among others, there are the following:
  • Piezoresistive
  • piezoelectric

 

  • capacitive and
  • inductive pressure sensors.

 

Design and function are much alike regardless of the measuring principle. A diaphragm separates two systems with different pressures. The pressure difference deforms the diaphragm. This deformation enables pressure measurement.

Pressure sensors from autosen use piezoresistive and capacitive measuring principles. Stainless steel thick film measuring cells are characterised by a robust and compact design, while the ceramic-capacitive measuring cell is particularly durable.
 

Ceramic-capacitive measuring principle

The ceramic-capacitive measuring cell is made up of a ceramic diaphragm and a base body. Electrodes are mounted on both elements that together from a capacitor and a reference capacitor. The diaphragm is deformed by the effective pressure and cause the electrodes to approximate and the capacity to change. The change in capacity is converted into an electric signal in the electronics, for autosen i.e. 4 … 20 mA.

Stainless steel thick film or Wheatstone bridge

The stainless steel thick film measuring cell is made up of a stainless steel diaphragm on which four electric resistors are interconnected as a Wheatstone bridge. If the sensor is now mounted in a system with the pressure, the diaphragm bulges. The electric resistors are firmly mounted on the diaphragm and also deform. This causes the electric resistance to change. The resistance change is measured in the Wheatstone bridge. The electronics converts the measured value into a standard signal um, for autosen i.e. 4 … 20 mA.
 

Advantages/features of a pressure sensor

With a range of different measuring cells and output functions as well as a variety of housing designs, pressure transducers can be used for all industrial processes requiring exact determination of data on pressures in gases or liquids.
 

Highest accuracies, best quality

They are very accurate and this capacity to measure pressures exactly can lead to higher productivity and lower costs. Even under extreme conditions and extreme pressures they function reliably and precisely.

Insensitive to pressure peaks

Pressure sensors from autosen can withstand dynamic pressure shocks and guarantee a high degree of overload protection – even where extreme pressure peaks occur as can be the case with fast-closing valves, for instance. We demand the highest standards when it comes to process reliability and quality.
 

Robust and durable

Thanks to their robust housing and the lack of moving parts, pressure sensors are able to withstand shocks and vibration and operate maintenance and wear-free.

High IP protection rating

The high IP protection rating enables use in the toughest conditions without impairing the sensor function by dust and cleaning processes.
 

Flexible use, broad pressure measuring ranges and vacuum

Our product line is designed for flexible use and covers broad pressure measuring ranges. Some of our sensors, transmitters and switches can also measure negative pressure and vacuum. These sensors for the negative pressure range are AP006, AP007, AP011, AP021, AP022 and AP023.

Plug & Play:

With a broad spectrum of process connection options, pressure sensors can be implemented easily and without much effort.
 

Fields of application

Pressure sensors are used in diverse ranges of application in numerous industries. It is especially in process technology and process engineering that it is crucial to monitor the process pressure to ensure process reliability and the quality of the final product.

Typical applications of pressure sensors are:
  • vacuum regulation
  • measurement of hydrostatic pressures in the food and beverage industry

 

  • measurement of system pressures of oil in hydraulic systems or
  • detection of the hydrostatic pressure in tanks.

 

 

Conversion table for pressure units

Pressure
Pa
mbar
H2O
psi
Torr
1 Pa =
1
0.01
0.102 mm
0.000145
0.0075
1 hPa =
100
1
10.2 mm
0.0145
0.75
1 bar =
100 000
1000
10.2 m
14.5
750.2
1 m H2O =
9810
98.10
1000 mm
1.422
73.56
1 psi =
6895
68.95
0.703 m
1
51.72
1 Torr =
133.33
1.333
13.6 mm
0.01933
1
 

Measuring ranges and rating of pressure sensors

 
Measuring ranges and rating of pressure sensors
 

Measuring range:

The sensor is rated for operation within a specified measuring range. Within this range the output signal behaves almost proportional to the measured pressure and satisfies the measurement accuracy specified in the data sheet.


Overload range:

Operation outside the specified measuring range, i.e. the overload range, however does not cause remaining damage to the sensor but the accuracy and the sensor behaviour may deviate from the data in the data sheet.


Destruction range:

The range above the overload limit is referred to as destruction range. Pressures occurring in this range this will cause irreversible damage to the device even in case of short-term exposure. The sensor fails completely and becomes unusable even if this cannot be seen from the outside. The bursting pressure is the mechanical load limit of the housing. When the bursting pressure is exceeded the housing is destroyed and medium may leak out undesirably.

It must always be observed when carefully selecting the appropriate pressure sensor that pressure peaks in the destruction range never occur. Reliable measurement according to the data in the data sheet is ensured only in the specified measuring range.

Underload range:

If the starting point of the measuring range of a sensor corresponds to atmospheric pressure, negative pressure or vacuum may be referred to as underload range. Operation in the underload range will not result in damage to the device. However, taking reliable measurements is not possible because either the signal is too weak or the sensor is technically unable to do this. Sensors capable of measuring up to the vacuum have no underload range but measure with greater inaccuracy at very small pressures (example: AP023).

 
Light bulb
It must always be observed when carefully selecting the appropriate pressure sensor that pressure peaks in the destruction range never occur. Reliable measurement according to the data in the data sheet is ensured only in the specified measuring range.

Accuracy data in data sheet

Linearity deviation

Linearity deviation specifies the maximum deviation from the straight connecting the zero point of the measuring range with the terminal point/ full-scale deflection. There is a linear relationship between the position/distance to be detected and the output signal.

Long-term stability

Pressure sensors are factory-calibrated to the data in the data sheet. The accuracy of the device may change over time. The long-term stability specifies the maximum change of zero signal and output span during a year.

Switching point accuracy

Switch point accuracy specifies the maximum measurement deviation of an adjusted value if linearity deviation, repeatability and long-term stability are observed.

Repeatability

Repeatability specifies the maximum measurement deviation when a process value is measured repeatedly.

Resolution

Resolution specifies the smallest physical deviation which can still be detected by the measuring system.

Temperature-dependent measurement deviation

The accuracy data of a pressure sensor are referred to a reference temperature; in most cases 25 °C. There are many applications with which very high or very low temperatures occur. Temperature conditions influence the sensor accuracy and therefore a temperature error has to be included in the calculation. Pressure sensors from autosen are in most cases temperature-compensated for the applicable measuring range to ensure reliable and accurate measurements.