Other Types of Pressure Measurement Devices

Ch 1, Lesson E, Page 7 - Other Types of Pressure Measurement Devices

• Common pressure measurement devices include the Bourdon Gauge and the pressure transducer.
• Pressure gauges are common in existing industrial plants, but pressure transducers are more common in laboratories and are becoming more common in new industrial plants.
• Two C-type Bourdon Gauges are shown here.
• At atmospheric pressure the curled tube inside the gauge is undeflected or relaxed and the gauge reads a GAUGE pressure of ZERO.
• At higher pressures, the Bourdon tube begins to uncoil.
• This action is translated into a rotation of the gauge needle by a series of gears.
• This gauge reads 8.5 atm GAUGE because the pressure within the tank is 8.5 atm above atmospheric pressure.
• There are many different types of Bourdon Gauges.  The C-type is just the easiest to sketch !
• They all work in a very similar manner.
• Pressure transducers are entirely different.
• Usually, pressure transducers work by measuring the deflection of a diaphragm placed between two regions at different pressures.
• When the transducer is built to read absolute pressure, one side of the diaphragm is exposed only to a vacuum.
• Transducers designed to read gauge pressure have one side open to the atmosphere.
• In either case, the deflection of the diaphragm is generally measured using strain gauges.
• Pressure transducers are small, inexpensive and rugged.
• In addition, because they produce an electrical signal, it is very easy to digitize the signal and record the pressure.
• That explains why they have become so popular.
• Now, let’s wrap us this lesson with a look at temperature and temperature measuring devices.