TITEL OF PRESENTATION :- ANALOG MEASURING INSTRUMENTS PREPARATION NAME ENROLLMENT NO.:  MR.SAVALIYA SURESH T  MR. SAVALIYA VISHAL H  MR.THUMMAR MAHENDRA V  MR. RANA KETAN  MISS. PATEL BHAVINI S BY GUIDED :- - MISS. PATEL ROSANI MAHATMA GANDI INST. OF TECHNICAL EDUCATION & RESEARCH CENTRE, VAVSARI.

PERMANENT MAGNET MOVING COIL METERS [PMMC]:  PRINCIPLE: When current carrying conductor is placed in the magnetic field, force is exerted on the conductor.  CONSTRUCTION:

 WORKING : When current flow in coil, current carrying coil is placed in magnetic field, force is develop. the magnitude of the force is F = NBIL Where, N= no. of turns of coil B= flux density wb/m2, I = current flowing through the coil. L= length of conductor in m, the force acts in opposite direction on two coil sides producing the deflecting torque, Td = Force * distance = NBIL * 2r = [2rNBL] *I = Kd * I,Where Kd =constant torque, Td is proportional to the current, and Tc is proportional to the deflation of point in degree, Tc = Kc * deflation of the point in degree, deflation of the point in degree is proportional to the current, Tc =Td

 ADVANTAGE: I. The scale is uniformly divided, II. Power consumption is very low, III. The torque-weight ratio is high, which gives a high accuracy. IV. no hysteresis loss and error.  DISADVANTAGE: I. These instrument are useful only D.C. II. Cost of these instruments is higher than that of moving iron instrument.

ELECTRODYNAMOMETER TYPE INSTRUMENTS:  PRINCIPLE: When current carrying conductor is placed in the magnetic field, force is exerted on the conductor.  CONSTRUCTION:

 WORKING: Here two fixed coil are used to create the magnetic field, two fixed coil and moving coil are connected in series. When current carrying coils, it produces the magnetic field and current carrying moving coil is placed in a magnetic field, hence force is exerted over the moving coil and it gives deflection. deflection torque: Td = KBIL = KBImL, Im is current flow in moving coil. flux density [B] is proportional to the current flow in fixed coil. But fixed and moving coil are connected in series. so Im = If, so, deflection torque is proportional to the square of current. Also proportional to the deflation of the point in degree, controlling torque = deflection torque

 ADVANTAGES : I. The coil are air cored, so instrument are free from hysteresis and eddy loss or error. II. These instruments can be used on both AC and DC.  DISADVANTAGES: I. They have non-uniform scale, II. Low torque to weight ratio as compared to PMMC. III. They are more costly than PMMC Type.

ELECTROSTATIC INSTRUMENTS :  CONSTRUCTION: [a] when one of the plates is fixed and other plate is free to move, plates are oppositely charged in order to have attractive force between them. Now due this attractive force movable plate will move towards the stationary or fixed plate till the moving plate stored maxi. Electrostatic energy. [b] in other arrangement there may be force of attraction or repulsion or both, due to some rotary of plate.

 WORKING: Plate A is positively charged and plate B is negatively charged. As mentioned above as per the possible condition [a], we have linear motion between the plate B is free to move, let us assume there exists some force F between the two plates at equilibrium, when electrostatic force become equal to spring force. At this point the electrostatic energy stored in the plates is, 1/2CV2. now suppose we increase the applied voltage by an amount dV, due to this the plate B moves towards the plates A by a distance dX, the work done against the spring force due to displacement of the plate B be F*dX, the applied voltage is related to current as, I = C dv / dt + V dc / dt, input energy is : Vi dt = v2 dc +CV dv. stored energy : ½ v2 dc + CV dv. input energy to the system = increase in stored energy +mechanical work done.;.v2 dc + CV dv = 1/2v2 dc +CV dc + F dx : F = 1/2v2 dc / dx

 ADVANTAGES : I. The coil are air cored, so instrument are free from hysteresis and eddy loss or error. II. These instruments can be used on both AC and DC. III. They are particularly suited for high voltage.  DISADANTAGES: I. Their scale is not uniform. II. The operating force are small. III. These instrument are costly.

THERMOCOUPLE INSTRUMENT:  PRINCIPLE: To convert heat energy to electrical energy at the junction of two conductors.  CONSTRUCTION:

 WORKING: When two metals having different work functions are placed to gather a voltage is generated at the junction, which is nearly proportional to the temperature. This junction is called a thermocouple. the heat at the junction is produced by the electrical current flowing in the heater element while the thermocouple produced on EMF at it’s output terminals, which can be measured with the help of a PMMC instrument the scale of PMMC instrument can be calibrated to read the current passing through the heater. let us consider temperature of the heater element be Ta and the temperature of cold metal be Tb. the generated emf at the junction is related to temperature difference as: e = a[Ta – Tb]+b[Ta - Tb]2, where a and b are constant whose value completely depends upon the type of metal we are using.

 ADVANTAGES : I. They may be used on both AC and DC. II. These instrument have a high sensitivity. III. These instruments can measure current in the range of 0.5A to 20A.  DISADVANTAGES : I. Temperature is proportional to the square of current. more loss I 2 R. Consumes high power, II. Overall efficiency of the system is low.

RECTIFIER TYPE INSTRUMENTS:  CONSTRUCTION:

 WORKING: Rectifier type instruments are used for measurement of AC voltage and currents by employing a rectifier element, which converts AC to a unidirectional DC and then using a meter responsive to DC to indicate the value of rectifier AC the indicating instrument is PMMC instrument. rectifier instrument are particularly suited to measurement on communication circuit and for all other light current work, where the voltage are low and resistance high, current drawn by the voltmeter does not exceed say. Multiplier resistance is used to limit the value of the current, in order that it does not exceed the current ratting of PMMC instrument.

 ADVANTAGES : I. The freq. range extends from about 20Hz to high audio freq. in MHz. II. They have a practically uniform scale for most ranges. III. Their accuracy is about +/- 5% under normal operating condition. IV. These instrument have a much lower operating current for voltmeter.

CONCLUSION  To prepare this presentation we have study that diffent type of anlog instrument and it’s construction and working.