3. 1. The measurement of electric current strength is
not always easy, especially when the measured signal
requires further electronic conditioning.
2. Simply connecting an ammeter to an electrical
circuit and reading out the value is no longer enough.
3. The current signal must be fed into a computer in
which sensors convert current into a proportional
voltage with minimal influence on the measured
circuit.
4. 1.The oldest technique is to measure the voltage
drop across a resistor placed in the current path.
2. To minimize energy losses the resistor is kept very
small, so the measured voltage must be highly
amplified.
3.Another widespread principle is the transformer. Its
construction is much simpler, but it doesn’t allow the
measurement of DC signals.
6. 1.Hall sensors measure the magnetic field
surrounding the conductor but, unlike current
transformers, they also sense DC currents.
2. A circular core of soft magnetic material is placed
around the conductor to concentrate the field.
3. The Hall element, which is placed in a small air
gap, delivers a voltage that is proportional to the
measured current.
8. 1.In open loop, the amplified output signal of the Hall element
is directly used as the measurement value.
2. The linearity depends on that of the magnetic core. The
price of these sensors is low, but so is their sensitivity.
3.Closed-loop Hall sensors are much more precise.
4.The Hall voltage is first highly amplified, and the amplifier’s
output current then flows through a compensation coil on the
magnetic core (Figure 1)
5. Closed-loop current sensors work up to frequencies of ~150
kHz.
10. 1.Magnetic field sensors based on the magneto resistive effect
are easily fabricated by means of thin film technologies.
2.They have been in production for years in many different
executions.
3.To reduce the temperature dependence, they are usually
configured as a half or a full bridge.
4 In one arm of the bridge, the barber poles are placed in
opposite directions above the two magneto resistors, so that in
the presence of a magnetic field the value of the first resistor
increases and the value of the second decreases (Figure 2).
12. 1.A very clever and cost-effective solution for the
measurement of high currents, especially in series
applications, was presented at PCIM’99 in Nuremberg,
Germany.
2.In this execution, the current is directly measured in the
primary conductor and the sensor module is then simply
clipped into a slot made in the conductor.
3.The sensor is mounted on an appropriate substrate and
encapsulated in a plastic package (Figure 3). With this
sensor, a broad range of currents can be measured simply
by adapting the geometry of the conductor.
HOW IT WORKS
14. 1. Significantly smaller volume and weight compared to
conventional current sensors, permitting greater flexibility
in application-specific design
2. No remanence in the event of overload
3. Measurement of DC and AC currents without additional
loss
4. Wide frequency range due to low inductive design
5. No auxiliary supply necessary on the level of current to be
measured
6. Low system costs
15. > CURRENT SENSORS IN TOMORROW’S CARS
1.Fuel efficiency first—this is the present motto of automotive
development worldwide.
2. Many components that are at present powered by the car’s
engine will in the near future operate on electricity—air
conditioning compressors, water pumps, oil pumps, and the
like.
3. Due to continuously changing engine speed, these
components have rather poor efficiency ratings. Electric
motors have the capability of optimizing their operation,
independent of engine speed.
16. A new generation of current sensors
Based on the magneto resistive effect
Is extremely compact and offers tight
Measurement tolerances and a high
Band-width at a low price.
17. 1.We can conclude that the universal current sensor
provide greater flexibility in application-specific design.
2. The universal current sensor is immune to
perturbations in the lead fibers.
3.There is no remanence in event of overload.
4.Measurement OF AC & DC current is possible without
additional loss.
18. References
1. H. Lemme. 1998. “Magnetfeld-Sen soren-
vielseitige Helfer,” Elektronik, H.3, S.40.
2. A. Petersen. 1985. “Magnetoresistive Sen soren
im Kfz,” Elektronik, H.10, S.99–102.
3. G. Reiniger. 1986. “Drehwinkel mes sung mit
Magnetfeldsensoren,” Elektronik, H.23, S.129.
4. projectsreport.org/tag/file-type-semina-report-
on-universal-current-sensor
5.https://www.maximintegrated.com/en/glossary/
definitions.mvp/.../Current-Sensor/.../6...
