21-02-2010, 05:35 PM
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UNIVERSAL CURRENT SENSORS
INTRODUCTION
MEASUREMENT OF ELECTRIC CURRENT STRENGHT IS DIFFICULT FOR ELECTRONIC CONDITIONING
CONNECTING AMMETER AND READING OUT VALUES ARE NOT VALID
GALVANIC ISOLATION AND BAND WIDTH
PHYSICALLY LARGE AND TECHNICALLY COMPLEX
SENSORS
IMPORTANCE OF SENSORS
* CURRENT IS FED TO COMPUTERS IN
WHICH SENSORS CONVERT IT TO
PREPOTIONAL VOLTAGE
* MINIMUM INFLUENCE ON MEASURED CIRCUT
EARLIER SOLUTIONS
1. TO MEASURE VOLTAGE DROP ACROSS RESISTOR PLACED IN CURRENT PATH
USE A TRANSFORMER
HALL CURRENT SENSORS
CONSTRUCTION AND TYPE OF HALL SENSORS
CONSTRUCTION
CIRCULAR CORE OF SOFT MAGNETIC MATERIAL
HALL ELEMENT TO PRODUCE PREPOTIONATE VOLTAGE
AMPLIFIER
TYPES
OPEN LOOP AND CLOSED LOOP
COMPARISON OF OPEN LOOP AND CLOSED LOOP SENSORS
OPEN LOOP
AMPLIFIED OUTPUT OF HALL ELEMENT IS DIRECTLY USED AS MEASURED VALUE
PRICE AND SENSITIVITY IS LOW
CLOSED LOOP
A COMPENSATION COIL IS WOUND AROUND MAGNETIC CORE
NON LINEARITY AND TEMPERATURE DEPENDANCE ARE REDUCED
NOT CHEAP AND BULKY FOR HIGH CURRENTS
MAGNETO RESISTIVE EFFECT
SLIGHT CHANGES IN RESISTANCE WHEN FERRO MAGNETIC MATERIALS ARE PLACED IN MAGNETIC FIELD
A PREFFERD ORIENTATION OF MAGNETISATION WHEN EXPOSED TO MAGNETIC FIELD
MAGNETIC MOMENT ALONG LINEAR AXIS COULD BE CHANGED BY APPLYING MAGNETIC FIELD WHICH RESULT IN INCREASE IN CURRENT
ADVANTAGES OF MAGNETO RESISTORS
CONFIGURED AS WHEATSTONE BRIDGE
USED AT HIGH FREQUANCY
USED AT HIGH TEMPERATURE
HIGH SENSITIVITY
CONSTRUCTION
CONFIGURED AS FULL BRIDGE WITH BABER POLES PLACED IN OPPOSITE DIRECTION TO IMPROVE TEMPERATURE DEPENDANCE
ELECTRICALLY ISOLATED ALUMINIUM COMPENSATION CONDUCTORS ARE USED ON SAME SUBSTRATE ABOVE PERMALLOY RESISTORS TO IMPROVE LINEARITY
VOLTAGE DROP ACROSS RESISTOR FORMS ELECTRICAL OUTPUT SIGNAL
PRIMARY CONDUCTORIS U SHAPED
FEATURES
1. NO MAGNETIC SHIELDING NEEDED
2. LINEARITY ERROR<.1%
OFFSET VOLTAGE<10MV
3.POWERED BY STANDARD BIPOLAR VOLTAGE OF +OR- 15
4. POWER CONSUMPTION IS 320MWTO 640MW
5.NO REMANENENCE
OUTPUT CAN BE SCALED FOR A/D CONVERTERS
COMPARATOR TO MEASURE SHORTCIRCUIT CURRENT
NO REMANENCE DUE TO ABSENSE OF CORE
COMPESATION PRODUCE HIGH LINEARITY
ADVANTAGES
SMALLER VOLUME AND WEIGHT COMPARED TO CONVENTIONAL CURRENT SENSOR
NO REMANENCE IN THE EVENT OF OVERLOAD
MEASUREMENT OF DC AND AC CURRENT WITH OUT ADDITIONAL LOSSES
WIDE FREQUANCY RANGE
LOW SYSTEM COST
APPLICATION
INVERTERS AND SERVO REGULATORS
ENERGY DISTRIBUTION
POWER ELECTRONICS SYSTEM
BATTERY MANAGEMENT
UNINTERRUPTABLE POWER SUPPLIES
ROBOTICS AUTOMOTIVE
RECENT DEVELOPMENTS
SENSOR MODULE IS REALISED AS DIL CHIP
MOUNTED ON POWER PCB BOARD
BUS BAR IS ALIGNED AS BUS BAR PLATE
LATEST MR SENSORS
PRIMARY CONDUCTOR IS USUALLY FLAT
SENSOR MODULE IS CLIPPED INTO A SLOT MADE IN IT
SENSORS ARE MOUNTED ON SUBSTRATE AND ENCAPSULATED IN PLASTIC
THEY ARE SMALL COMPACT LIGHT CHEAP AND EASY TO MOUNT
PRIMARY CONDUCTOR IS PART OF APPLICATION
CURRENT SENSORS IN TOMMORROWS CARS
¢ MANY COMPONENTS OPERATED BY CARS ENGINE WILL IN FUTURE OPERATE ON ELECTRICITY
¢ ACCORDING TO NEW PROTOTYPE PRESENT AT MANNESMANN-SACHS AG AT 1999 IAA CAR EXHIBITION IN GERMANY A STARTER GENERATOR I S USED
¢ IT REQUIRE THREE PHASE MOSFET ALTERNATOR
¢ 2 PHASES REQUIRE MAGNETO RESISTANCE CURRENT SENSORS
CONCLUSION
MAGNETO RESISTIVE SENSORS ARE A GROUP OF SENSORS WHICH HAVE BOUGHT FAST AND REVOLUTIONARY CHANGES IN CURRENT MEASUREMENT AND ITS CONDITIONING .
ATTEMPTS ARE GOING ON TO MAKE IT MORE USER FRIENDLY
IN THE NEXT FEW DECADES MAGNETO RESISTORS AND ITS SENSORS ARE PREDICTED TO REPLACE THE CONVENTIONAL RESISTORS IN ALL APPLICATION
