The History of Pressure Measurement

Galileo Galilei, born in Pisa (Italy), obtains the patent
for a machine to pump water from a river for the irrigation of
land. The heart of the pump was a syringe. Galileo Galilei
found that 10 meters was the limit to which the water would
rise in the suction pump, but had no explanation for this
phenomenon. Scientists were then devoted to find the cause for this.

1644 Evangelista Torricelli (rorr). Italian physicist, filled a
tube 1 meter long, hermetically closed at one end, with
mercury and set it vertically with the open end in a basin
of mercury. The column of mercury invariably fell to about
760 mm, leaving an empty space above its level. Torricelli
attributed the cause of the phenomenon to a force on the
surface of the earth, without knowing, where it came from. He also
concluded that the space on top of the tube is empty, that nothing
is in there and called it a "vacuum".

1648 Blaise Pascal, French philosophei physicist and
mathematician, heard about the experiments of Torricelli
and was searching for the reasons of Galileo's and Torricelli's
findings. He came to the conviction that the force, which
keeps the column at 760 mm, is the weight of the air above.
Thus, on a mountain, the force must be reduced by the weight of
the air between the valley and the mountain. He predicted that the
height of the column would decrease which he proved with his
experiments at the mountain Puy de Dome in central France. From
the decrease he could calculate the weight of the air. Pascal also
formulated that this force, he called it "pressure", is acting uniformly
in all directions.

1656 Offo von Guericke, born in Magdeburg/Germany.
Torricellis conclusion of an empty space or "nothingness"
was contrary to the doctrine of an omnipresent God and
was thus attacked by the church. Guericke developed
new air pumps to evacuate larger volumes and staged a
dramatic experiment in Magdeburg by pumping the air out of two
metal hemispheres which had been fitted together with nothing
more than grease. 8 horses at each hemisphere were not strong
enough to separate them.

1661 Robert Boyle. an Anglo-Irish chemist, used "J"-shaped
tubes closed at one end to study the relationship between
the pressure and volume of trapped gas and stated the law
of x V = K (P: Pressure, V: Volume, K: Constant) which
means that if the volume of a gas at a given pressure is
known, the pressure can be calculated if the volume is changed,
provided that neither the temperature nor the amount of gas is changed.

1820 Almost 200 years later, Joseph Louis Gay-Lussac.
French physicist and chemist, detects that the pressure
increase of a trapped gas at constant volume is proportional
to the temperature. 20 years later, William Thomson
(Lord Kelvin) defines the absolute temperature

Mechanical Measurement Technologies

1843 Lucien Vidie, French scientist, invented and
built the aneroid barometer, which uses a spring
balance instead of a liquid to measure atmospheric
pressure. The spring extension under pressure is
mechanically amplified on an indicator system.
Employing the indicator method of Vidie, Eugene
Bourdon (founder of the Bourdon Sedeme Company) patented 1849
the Bourdon tube pressure gauge for higher pressures.

Electrical Measurement Technologies

1930 The first pressure transducers were transduction
mechanisms where the movements of diaphragms, springs
or Bourdon tubes are part of an electrical quantity.
Pressure diaphragms are part of a capacitance. the
indicator movement is the tap of a potentiometer.

1938 The bonded strain gauges were independently
developed by E. E. Simmons of the California Institute
of Technology and AC. Ruge of Massachuseffs Institute
of Technology. Simmons was faster to apply for a patent.

1955 The first foil strain gauges came up with an integrated full
resistor bridge, which, if bonded on a diaphragm. see opposite stress
in the center and at the edge.

1965 The bonding connection of the gauges to the diaphragm was
always the cause for hysteresis and instability. In the 1960's,
Statham introduced the first thin-film transducers with good stability
and low hysteresis. Today, the technology is a major player on the
market for high pressure.

1973 William R. Poyle applied for a patent for capacitive
transducers on glass or quartz basis, Bob Bell of Kavlico
on ceramic basis a few years later in 1979. This technology
filled the gap for lower pressure ranges (for which thin
film was not suited) and is today, also with resistors on
ceramic diaphragms, the widest spread technology for
non-benign media.

The Sensor Age

1967 Honeywell Research Center, Minneapolis/USA, 1967:
Art R. Zias and John Egan applied for patent for the
edge-constrained silicon diaphragm. 1969. Hans W. Keller
applied for patent for the batch-fabricated silicon sensor.
The technology is profiting from the enormous progresses
of IC-technology.

A modern sensor typically weighs 0.01 grams. If all non-cristalline
diaphragms have inherent hysteresis, the precision limit of this item
is not detectable by todays means.

2000 The piezoresistive technology is the most universal one. It applies
for pressure ranges from 100 mbar to 1500 bar in the absolute, gauge
and differential pressure mode. The slow spread of the technology in
high volume applications for non-benign media resulted from the inability
of US-companies to develop a decent housing. In 30 years, KELLER has
perfected it at costs comparable to any other technology.

For more information, please contact... KELLER at

For details of Pressure Sensors Suppliers, click here...


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