Water Level Control by Feedback Method
Military Institute of Science & Technology
Aero Instrumentation and Measurement Laboratory
AEAV-312
Exp No: - 01
Exp Name: - Water Level Control by Feedback Method.
Objectives: The Objective of this experiment is to control the level water by feedback transducer, and get familiar with the action of PID.
Theory: Measurement of level and pressure (analog type output) with pressure and level measurements, the pressure sensor set at the bottom of the vertical column of unit ty3oa/ev is used.
Definition of an Analog Variable:
An analog measurement ring permits the generation of a D.C. voltage which behavior follows the water level in the column; this means that each value of the column corresponds to only one value of the output voltage. So there is analogy between the level and the variable representing it (output voltage of the measurement system). We can say that a variable or information is analog when it varies in continuous, or when, it can not be discontinuous by its own nature. This means that an analog variable (in our case, the water level of the column) can take infinite values.
The Pressure Sensor
Under static condition, the level of a liquid is linked to pressure, according to a law of proportionality. If “L” represents the level, which is the height, of a liquid in a tank, the pressure at the bottom will is given by:
P = L.g.Ms where: P = Pressure ( in Pa (Pascal) = N•m-2 = 10-5 bar)
L = level (in m) g = acceleration of gravity (g = 9.81 m.s-2)
Ms= specific mass of the liquid (kg.m-3).
Consequently, it is sufficient to measure the pressure to obtain the level. Among the different available pressure transducers, the STRAIN GAUGE ones have become the mostly used.
The operating principle of these transducers is the piezoresistivity (property of the materials which change their resistance as function of the deformation to which they are subjected).
The four resistors connected at Whetstone’s bridge are taken from a
Aero Instrumentation and Measurement Laboratory
AEAV-312
Exp No: - 01
Exp Name: - Water Level Control by Feedback Method.
Objectives: The Objective of this experiment is to control the level water by feedback transducer, and get familiar with the action of PID.
Theory: Measurement of level and pressure (analog type output) with pressure and level measurements, the pressure sensor set at the bottom of the vertical column of unit ty3oa/ev is used.
Definition of an Analog Variable:
An analog measurement ring permits the generation of a D.C. voltage which behavior follows the water level in the column; this means that each value of the column corresponds to only one value of the output voltage. So there is analogy between the level and the variable representing it (output voltage of the measurement system). We can say that a variable or information is analog when it varies in continuous, or when, it can not be discontinuous by its own nature. This means that an analog variable (in our case, the water level of the column) can take infinite values.
The Pressure Sensor
Under static condition, the level of a liquid is linked to pressure, according to a law of proportionality. If “L” represents the level, which is the height, of a liquid in a tank, the pressure at the bottom will is given by:
P = L.g.Ms where: P = Pressure ( in Pa (Pascal) = N•m-2 = 10-5 bar)
L = level (in m) g = acceleration of gravity (g = 9.81 m.s-2)
Ms= specific mass of the liquid (kg.m-3).
Consequently, it is sufficient to measure the pressure to obtain the level. Among the different available pressure transducers, the STRAIN GAUGE ones have become the mostly used.
The operating principle of these transducers is the piezoresistivity (property of the materials which change their resistance as function of the deformation to which they are subjected).
The four resistors connected at Whetstone’s bridge are taken from a