Servomotor Mechanism | Plate Earthing

Servomotor Mechanism :

~ By servo-mechanism or simply a servo, we mean , system which is used to automatically control the output mechanical position, or time derivative of position, viz velocity or acceleration of the output member, in response to variations of input signal.

~ As such, a servo system is used to position a final control element in a generalized instrumentation system.
~ Servo-mechanism has found number of applications in industry, such as in tool position control, radar tracking systems, misslle guidance system etc.

~ Actuators are used to operate the final control element such as a valve, heater, etc. It is an important element of servo-mechanism.

 A servo-mechanisin is a closed loop system that moves or changes the position of the controlled object so that it agrees with the position of a control device. In short servo may be considered, as any type of closed-loop system.

~ The error detector compares the feedback signal with the reference input or command and generates actuating signal.
~ Control element receives and amplifies the actuating signal so that larger external power is applied to restore the desired position of the controlled object.

~ A feedback element provides the true position of the object being controlled.
~ Actuator or error corrector is a part of control element. Other part of control element can be some form of amplifier. The large power, controlled by the amplifier, is applied to an actuator.
~ Actuator corrects the system error by causing the right change in controlled quantity. In servo-mechanism, this actuator must produce motion, either linear or rotary. Therefore, some type of thrust device (linear motion) or motor (rotary motion) is required so that it can work as an actuator. Bxamples are: soleloid valve, motor (AC and DC; stepper and servo), pneumatic valve, etc.

Plate Earthing

~ In case of plate earthing, plate electrodes may be made of galvanized iron or steel having thickness of not less than 6.30 mm.

~ If plate electrodes of copper are used these should have a thickness of not less than 3.15 mm.
~ The size of plate electrode should be 60 cm x 60 cm as shown in Fig. 14.2.5.
~ Plate electrode should be buried such that the top edge is at a depth of not less than 1.5 m below the surface of the ground.
~ For plate earthing a pit of a 4 meters is dug in to the ground and earth electrode (plate) is placed vertical in that pit.
~ The space around the plate is filled with layers of charcoal and salt for a minimum thickness of 15 cm.
~ For connection of earth wire to earth electrode, a G.I. pipe of 12.7 mm diameter is connected to electrode (plate).
~ Earth wire is properly connected to earth electrode with the help of nut, bolt and washer.
~ The pit filled with charcoal and salt also has a pipe for carrying water from concrete work to that area.
~ This will help in increasing the dampness and moisture surrounding the plate.