View A Video on Pressure Transducers - A Quick Introduction
Despite the imprecision of the label, the term "pressure transducer" can be used to describe a pressure sensor without creating much confusion, mostly because pressure transducers are applied almost exclusively as pressure sensors. Miniature sensors, pressure calibrators, pressure regulators, level transmitters and other pressure sensor varieties all require the use of pressure transducers to measure and report pressure levels in an area. Temperature transducers and torque transducers are also somewhat imprecisely named, but that imprecision does not typically cause confusion; they are also used to convert input energy into electrical energy for the purposes of measurement. Air pressure sensors are among the most common pressure sensors. The three main air pressure sensor categories, absolute pressure sensors, atmospheric pressure sensors and differential pressure sensors, distinguish themselves from each other based on how they measure air pressure relative to ambient pressure.
There are numerous varieties of pressure sensors, and they are classified according to the range of pressure they measure, the operating temperature range and the kind of pressure they measure. The five main categories of pressure sensors include absolute and differential sensors as well as gauge, vacuum and sealed pressure sensors. Absolute pressure is measured against a perfect vacuum, which is 0 pounds per square inch (PSI). Atmospheric pressure, for example, is ~14.7 PSI at sea level as measured by an absolute pressure sensor. An air pressure sensor determines the pressure of air flow and provides a convenient and accessible way to understand the reading. These sensors are typically used with air compressors or pneumatic tools. Barometric or atmospheric pressure sensors provide readings of the pressure from the so-called weight of the air and are frequently used in meteorology. Differential pressure sensors calculate the difference between two or more pressures as measured by various inputs in the unit. They measure drops in pressure and the rate of flow within enclosed or pressurized vessels. Miniature sensors are designed for use in critical medical or biological applications where instruments should provide a very low intrusion volume.
There are many different devices used to measure and describe pressure, and they are frequently combined into one mechanism or device that maximizes the information it provides. Pressure calibrators are devices that measure and report the pressure, level and flow of certain instruments in order to keep them operating safely and efficiently. They receive input from an established system and compare that information with what the system's gauge reads, allowing the operator to quickly determine whether the gauge is reading correctly or not. This is an important step in maintaining safe conditions. Pressure regulators monitor and control the amount of pressure running through a system. Typically they can be programmed to alert operators if the pressure exceeds a certain point in order to maintain safe conditions. Pressure is affected by a number of variables and therefore measured in a range of ways. The level of a solid, liquid or slurry in a specified space is measured by level transmitters that usually provide feedback in the form of an alarm or shut-off switch. Temperature transducers and torque transducers measure additional information such as heat content and rotational movement. To measure temperature, the sensor can be placed directly in the substance and measure its own temperature, or it can make a reading based on thermal radiation. Torque transmitters measure the twist in a rotating system, both static and dynamic.
Transducers, sensors and transmitters have been necessary since the Steam Age and have made substantial improvements since then. Advancements in materials and technology have allowed sensors and transducers to become smaller and more accurate. Modern materials include ceramic, copper, stainless steel and various other metals. For example, a typical pressure sensor is about a cubic inch in size but miniature sensors can be less than 1/100th that size. Most are accurate with less than one percent margin of error. They are used in critical situations and are kept reliable through proper calibration and backup systems. The integrated circuit, also known as an IC, microchip or silicon chip, is a miniaturized electronic circuit that is used in almost all electronic equipment today. Many sensors and transducers use chips to maintain accuracy and to communicate with other equipment. Modern sensors work based on the principle of piezoresistance, which is the observation that various amounts of pressure cause a material to conduct electricity at certain rates. The transducer receives the force from pressure and converts it to electrical energy. The charge is fed to a wire that reads it and can determine the pressure that was applied; a sensor then reads the information and displays it in a readable way.
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Pressure Transducer Types
- measure pressure regardless of ambient pressure conditions; in other words, absolute pressure sensors measure pressure in reference to an absolute vacuum as opposed to in reference to ambient air pressure.
- Air pressure sensors measure the force of air exerted on the device and then convert the information into a readable display.
- Atmospheric pressure sensors measure the force exerted by the weight of air and convert the information from electrical energy to a readable display.
- are instruments that detect fluid pressure and produce an electrical, mechanical, or pneumatic signal in response to the pressure.
- Level transmitters are devices that measure the level of a solid, liquid or slurry within a container then convert the information into a comprehensible form.
- Miniature pressure sensors are designed to unobtrusively measure the pressure of gases or liquids and then display the results in an understandable way.
- Pressure calibrators are devices that determine how accurately sensors are measuring pressure in order to keep them operating safely and efficiently.
- Pressure regulators monitor and control the pressure of gas and liquid passing through a system by opening and closing valves in order to match the flow of the fluid to the demand for it.
- for the purposes of pressure measurement perform well for a wide range of electronic
pressure measurement applications. They have a high-accuracy rate.
- fit most industrial pressure measurement
applications. The printed circuit board is potted in silicone gel for
protection against shock, vibration and humidity and uses state of
the art surface mount technology.
- are used to measure the pressure of gases or fluids. They are designed
to monitor changes in pressure and are often connected to safety
devices that activate shut-off switches. Pressure sensors use their
pressure readings to send a message to another mechanism.
- are used to measure, monitor, and transmit the pressure of liquids or gases.
- convert
pressure into an electrical signal by physically deforming strain gages,
which are bonded into the
diaphragm
of the pressure transducer. This introduces strain to the gages,
which then will produce an electrical resistance change proportional
to the
pressure.
- are specifically
designed for municipal liquid level measurements and a range of
other applications. Specifically, these transducers are used for water
and wastewater treatments, well depth measurements and offshore
water
depth
measurements and therefore use a watertight, high-strength vented
polyurethane cable, which is capable of complete submersion.
- Temperature transducers are devices that change an input of energy into a temperature reading.
- are instruments that measure torque on rotating systems.
- are devices that convert one type of energy into a different output form.
Pressure Transducers Terms
- The
combination of the error of nonlinearity, repeatability and hysteresis,
expressed as a percentage of full scale
output.
- A load applied alongside or parallel to and concentric
with the primary axis.
- The sensitivity of a sensor that is preferably
in a straight line but also usually has minute non-linearity. BFSL takes
all the data points from the curve and describes a straight line through
these data points so that the divergence (and thus the error) between
the curve and the straight line is at a minimum.
- The maximum amount of pressure that may be applied
to an object without the object rupturing.
- A test in which known values of pressure are applied to the instrument
and output readings are recorded under specific conditions.
- The volume of
the pressure port of a transducer at room temperature and barometric
pressure.
- The difference between the actual measured
pressure and a fixed reference point.
- The difference between the true value of the pressure that
is sensed and the value indicated by the transducer.
- The voltage or current applied to the input terminals
of the transducer to supply its proper operating conditions.
- Pressure measured relative to ambient pressure.
- The maximum difference in output within the range
when the value is approached with increasing pressure and then with decreasing
pressure for full range traverses.
- The maximum deviation of the calibration curve (average
of upscale and downscale readings) from a straight line positioned to
pass through the upper and lower range values.
- Undesirable signals that can increase the amount of error.
Examples of noise include radio frequency interference, electromagnetic
interference, hum from power lines and broadband or white noise.
- The electrical signal that results from applied pressure
to the transducer.
- The greatest pressure desired that is sensed during
a measurement session.
- An orderly change in pressure over a specific time.
- The closeness of agreement among a number of consecutive
measurements of the output for the same value of the input under the
same operating conditions, approaching from the same direction, for full
range traverses.
- The part of the transducer that reacts directly
as a response to pressure.
- A change
in the pressure that is being measured or controlled.
- The rated output signal of a transducer without
a load applied and rated excitation, typically articulated as a percent
of rated output.
