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In automotive application, thermistor is used for measuring the
temperature. Temperature
sensors measure engine coolant temperature, intake air
temperature and exhaust gas recirculation
etc. The NTC type of sensor is used and resistance is higher at
lower temperature. The decrease
in the resistance causes decrease in the voltage.
The temperature sensor circuit is tested for
Open circuit method. Short circuit method
Open cicuit method
1
Open circuit
To find the fault in the system, the jumper wire connected
across the temperature
terminals. The temperature should go in the high there is a
problem in the circuit. Open circuit is
for low temperatures.
Short circuit method
Short circuit method
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In an open circuit testing, as temperature increases there are
no decrease in the resistance.
This means that the circuit becomes shot and the sensor is not
working properly. Short circuit is
for high temperatures.
Need for the fault detection circuits and its advantages
/disadvantages
The basic need of the fault detection circuits gives
reliability. Sensors used in the
automotive system should be reliable, accurate, sensitive etc
for maximum tome period. Sensors
are exposed to water, dust and other materials; it fails to
perform its operation. This failure is
identified by the fault detecting circuit. The fault detecting
circuit is very essential in the
automotive industry. Now a day in vehicles, large numbers of
sensors are used for various
applications. So it is difficult task to monitor the failure of
each sensor. To overcome this, need a
fault detecting circuit which helps in detection of the failure
of each sensor in the vehicle and
replace the fault sensors.
The advantages are
Protection of the system from the malfunctioning in the sensors.
It makes the system stable by monitoring of the sensor with the
accuracy, sensitivity and
other performance parameters.
Using the resistors, capacitors and amplifiers, are made up of
semiconductors. So smallcircuits are cost effective.The
disadvantages are
The circuit itself is a fault. It means that fault detection
circuit is faulty then it givesimproper error values to the ECU. So
the system fails to detect the faults in the sensor.
Each of the sensors has many performance characteristics. For
controlling of the eachperformance requires individual fault
detection circuits. For this sensor system becomes
more complex from these circuits.
Sensor requires power for its operation. And fault detection
circuit also requires power tooperate. So the power consumption in
the system is more.
For each characteristics of the sensor requires separate
circuits. So the size and weight ofthe system becomes large.
By using MEMS technology, all the circuits are made to integrate
on the chip. But thecost becomes more than sensor.
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Market growth and challenges in design and development of the
fault detection circuits
The market growth is defined as an increase in the demand of a
particular product over a
time. The number of the sensors and actuators are using in the
vehicles increasing day by day. In
2010, more than 12 billion dollar used for sensor development.
For good sensor, the sensor must
be reliable and operating in all conditions. By monitoring this
sensor circuit is required. The
money spent for sensor development also consists of development
of fault detecting circuits. The
challenges are
The circuit is as simple as possible. The single circuit that
can used for multi operation. The faults detect circuit that can be
integrated on the sensor only.
Conclusion
By observing of the survey on the fault detecting circuits are
very essential for the proper
functioning of the system. And also it helps to increase safety
and performance. But the circuit
only detects the problems not diagnosing. In future development,
self diagnosis can be achieved
with the help of fault detecting circuits.
