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Transducers-Pressure measurment device.

Pressure is defined as the amount of forec applied to a surface or distributed over it and is measured as the force per unit area.
The force used to calculate the pressure must act at a right angle to the surface. Pressure instruments usually refer to those that are used for the measurement of the pressure exerted by a fluid. The essentails of perssure measurement are encompassed in the above definations and the following observations:

Pressure is strongly influenced by position within a static fluid but, at a given position, it is independent of direction.
Pressure is unaffected by the shape of the confining boundries.

Different types of Pressure

When pressure is measured, it is usually desired to read it in terms of
a) gauge pressure. Most liquid pressure use atmospheric pressure as a zero point. i.e they indicate a pressure of zero psi at the surface of a liquid even though the pressure is actually 14.7 psi.
b) absolute pressure Absolute pressure is acutal total pressure including atmospheric pressure.
c) Vacuum or Differential pressure. Gauges that indicate gauge pressure may be designed to indicate pressures below zero. Such a gauge is called vacuum gaure. Gauges indicate the abolute pressure cannot indicate pressures below zero, because zero is a perfect vacuum.

Methods of pressure measurement

Most pressure instruments measure a difference between two pressure, one usually being that of atmosphere. The different methods of pressure measurement are
a) Manometer method
b) Elastic pressure transducers
c) Pressure measurment by measuring vacuum
d) Pressure measurement by balancing the force produced on a know area by a measured force.
e) Electical pressure transducers.

Advantages of Elastic Pressure transducer

Elastic Pressure transducer cost is low.
Elastic Pressure transducer have simple construction
Elastic Pressure transducer have been time tested in applications.
Elastic Pressure transducer allow high accuracy, espatially in relation to cost.

Disadvantages of Elastic Pressure transducer

Elastic Pressure transducer have a low spring graident.
Elastic Pressure transducer are suscepitable to shock and vibration.
Elastic Pressure transducer are susceptile to hysteresis.

Advantages of Diaphragm Pressure Transducer

Diaphragm Pressure Transducer cost is moderate.
Diaphragm Pressure Transducer possess high over range characteristics.
Diaphragm Pressure Transducers are adaptable to absolute and differential pressure measurement.
Diaphragm Pressure Transducer have goog linearity.
Diaphragm Pressure Transducer are small in size.

Disadvantages of Diaphragm Pressure Transducer

Diaphragm Pressure Transducer lack good vibration and shock resistance
Diaphragm Pressure Transducers are difficult to repair.
Diaphragm Pressure Transducer are limited to relatively low pressures.

Strain Gauge Pressure Transducer

Strain gauge pressure transducer is a passive type resistance pressure transducer whose electrical resistance changes when it is streached or compressed. It can be attached to a pressure sensing diaphram.

Advantages

Strain Gauge Pressure Transducers are small and easy to install.
Strain Gauge Pressure Transducer have good accuracy.
Strain Gauge Pressure Transducer possess good stability.
Strain Gauge Pressure Transducer have high overrange capacity.
Strain Gauge Pressure Transducer contain no moving parts.

Other Pressure measuring devices.
Potentiometric Pressure Transducers.
Capacitve Pressure Transducers.
Reluctance Pressure Transducer.
Servo Pressure transducer.
Pieoelectric Pressure Transducer.