Thermocouple types of instruments give very accurate reading even at high frequency, thus these types of instruments are completely free from frequency errors.
The measurement of quantity under these instruments is not affected by stray magnetic fields.
These instruments are known for their high sensitivity.
Usually for measuring the low value of current bridge type of arrangement is used i.e. ranging from 0.5 Amperes to 20 Amperes while for measuring the higher value of current heater element is required to retain accuracy.
Disadvantages of Thermocouple Type Instruments:
Synchro Position Transducer Working Principle:
Construction Of Position Transducer:
Position Transducer Working Principle:
We know that the stator of the synchro has three windings. These three winding of the stator are connected in star connection. Remaining ends of each winding are taken out to connect them with the voltmeter as shown in the figure. When the angle of the rotor changes the output voltage i.e. the stator voltages of each winding is given by,
E1 = Eom cosθ sin wt = instantaneous voltage for stator windings S1.
E1 = Eom cos(θ+120) sin wt = instantaneous voltage for stator windings S2.
E1 = Eom cos(θ+240) sin wt = instantaneous voltage for stator windings S3.
θ= angular position of the rotor
Eom = peak value of voltage of each winding
f= frequency of the rotor
t = time in seconds.
All instantaneous voltages are sinusoidal in nature. But they give different values of voltages at different positions of the rotor.Thus using these three values of stator voltages we can easily measure the position of the rotor. Hence Synchro can be used as a position transducer.
Applications Of Position Transducer:
For measuring the angle of the rotating machine like antenna platform.
Position transducer can be used as rotary position sensor for aircraft control surfaces