Analog Electronics Process Controllers: An Analog Electronics Process Controllers must be capable of providing one or more of the three main methods of control, namely, Proportional, Integral and Derivative. The circuits described in this section use high gain OPAMP’S with specially designed feedback circuits. They operate with their phase inverting input as a virtual earth …
Define Offset Error: Define Offset Error – Proportional control action is characterized by a permanent residual error in the operating point of the controlled variable when a change in load occurs. This error is called the OFFSET. The offset can be reduced by selecting higher value of controller gain (KP) corresponding to narrow bandwidth. Figure 21.6 …
Proportional Controller: In many processes, the cycling that occurs with the two position ON—OFF control is undesirable. Steady process controlled in the absence of noises, is possible when the controlled variable is a continuous function of the error. A most widely used form of continuous control mode is the proportional control action, in which a …
On Off Controller or Two Position Controller: The On Off Controller or two position controller is the simplest, cheapest and the most used controllers. It is used in domestic heating systems, refrigeration, water tanks, etc. When the measured variable is below the set point, the controller is ON and the output signal has maximum value. …
Step Function Response: The step function response consists of applying an instantaneous change in the control means and then recording graphically the result of the change on the measured variable. This graphical record obtained in response to the step excitation is called the Process Reaction curve. Two typical process reaction curves are shown in Fig. …
Basic Automatic Control: Multivariable systems are used more commonly in this age of Basic Automatic Control. Control parameters are becoming more complex by the day and the range of applications wider. In such complex systems, there are more than one input along with noise signals which are also present and there are more than one …
Standing Wave Ratio Measurements: Standing wave are created along the length of a transmission line due to the mismatch between the characteristic impedance Z0 and the terminating impedance of the transmission line. The actual voltage E on the line at any point is the sum (Ei + Er) of the voltage of the incident and …
Measurement of Power Transmission Lines: When power is applied to Measurement of Power Transmission Lines, the source to load impedance must be matched in its characteristics impedance (Z0). The impedance all along the line is equal to the characteristic impedance. Therefore, the transmission line is said to be correctly terminated. Hence no reflection or standing …
Heat Capacity of Calorimeter: Heat Capacity of Calorimeter – RF power may be directly converted into heat. Water acts as the load, and RF power may be used to heat an element such as a long transmission line, water being used as a coolant. The RF power may be absorbed directly in the calorimeter fluid. …
Bolometer: Bolometric measurements are based on the dissipation of RF power in a small temperature sensitive resistive element, called a Bolometer. This bolometer may be a short ultra thin wire having a positive temperature coefficient (PTC) of resistance, called Baretter, or a bead of semi-conductor having a negative temperature coefficient (NTC) called Thermistor. Both Baretters …