Sensor Data Chapt1

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SENSORS AND DATA

ACQUISITION

Mai Anh Tuan

Chapter 1

Data Acquisition

Mai Anh Tuan



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1.1 Sensors, Signals, and Systems

• Sensor: a “device that receives and responds

to a signal or stimulus.”


• Natural and human-made objects.

– Natural sensors: usually respond with signals,

having an electrochemical character, that is, their

physical nature is based on ion transport, like in

the nerve fibers (such as an optic nerve in the

fluid tank operator).

– Artificial: information transmitted and processed

in electrical form through the transport of e



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• Natural and human-made objects.

– Natural sensors: usually respond with signals,

having an electrochemical character, that is, their

physical nature is based on ion transport, like in

the nerve fibers (such as an optic nerve in the

fluid tank operator).

– Artificial: information transmitted and processed

in electrical form through the transport of e

YOUR TURN

• Q 1. list the natural sensors you may know

• Q2. list the man-made sensors you may know



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• A man-made sensor should be capable of

responding with signals where info carried by

displacement of e.

• Connect a sensor to an electronic system via

el. wires rather than an electrochemical

solution or a nerve fiber.


• Sensor responds to nonelectrical value(stimulus) and to convert it into an electricalsignal that is compatible with electroniccircuits.

• Electrical signal: can be channeled, amplified,and modified by electronic devices ~ outputsignal ~ V, I or charge in terms of amplitude,

polarity, frequency, phase, or digital code ~output signal format.



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• Sensor is an energy converter: that can be

reversible way (positive or negative).

• A special case: when net energy flow =0 which

also carries info. about existence of that

particular case.

– Thermopile infrared radiation sensor




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• Sensor vs. transducer

Ultrasonic Sensor Speaker as a X’ducer

1.1 Sensors, Signals, and SystemsSensor Transducer

Converts any type of energy into

electrical energy

Converter of any one type of energy

into another

Can be an actuator

May be parts of complex sensors as

depicted.



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• Two types: direct and complex

– Direct one converts a stimulus into an electrical

signal or modifies an electrical signal by using an

appropriate physical effect

– Complex sensor in addition needs one or more

X’ducers of energy before a direct one can be

employed to generate an electrical output.

YOUR TURN• Does a sensor function itself?

• No. It is always a part of a larger system that mayincorporate many other detectors, signalconditioners, signal processors, memorydevices, data recorders, and actuators.

• A sensor is always a part of some kind of a data

• acquisition system



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Fig. 1.3 Positions of sensors in a data acquisition system. Sensor 1 is noncontact,sensors 2 and 3 are passive, sensor 4 is active, and sensor 5 is internal to a dataacquisition system




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1.2 Sensor Classification

1. Two kinds: passive and active.

– A passive one does not need any additional

energy source and directly generates an electric

signal in response to an external stimulus. That

is, the input stimulus energy is converted by the

sensor into the output signal. Most of passive

sensors are direct sensors as we defined them

earlier.

1.2 Sensor Classification1. Passive and Active.

– A passive one does not need any additional

energy source and directly generates an electric

signal in response to an external stimulus. That

is, the input stimulus energy is converted by the

sensor into the output signal. Most of passive

sensors are direct sensors as we defined them

earlier.



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1. Passive

a) Photodiode

b) Thermopile (couple)

c) Piezoelectric sensor

(a) (b)

(c)

1.2 Sensor Classification1. Passive and Active.

– An active need an excitation signal (power) for

operation. That signal is modified by the sensor

to produce the output signal.

– Called parametric ‘cause their own properties

change in response to an external effect and

subsequently converted into el signals.

– A sensor’s parameter modulates the excitation

signal and that modulation carries info., of the

measured value.



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1. Passive and Active.

R (eristance) is function of V(oltage), I(current)


2. Absolute and Relative.

– An absolute sensor detects a stimulus in

reference to an absolute physical scale that is

independent of the measurement conditions,

whereas a relative sensor produces a signal that

relates to some special case.

– Eg. (1): Thermistor, a temperature-sensitive

resistor. R =f (TKelvin).

– Thermocouple is a relative sensor. V=f (dT). It

needs a reference.



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2. Absolute and Relative.

– Eg. (2). Pressure sensor.

Relative Absolute


3. Properties that may be of a specific interest.

Table 1.1 Sensor specifications



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Table 1.2 Sensor materials



Table 1.3 Detection means uded in sensor



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Table 1.4. Conversion phenomena



Table 1.5 Fields of application



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Table 1.5 stimulus

1.2 Sensor Classification3. Properties that may be of a specific interest.

Table 1.5 stimulus (cont.)



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1.2 Sensor Classification3. Properties that may be of a specific interest.




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1.3 Units of Measurements

• The 14th General Conference on Weights and

Measures (1971).

• SI ~ (Le Système International d’Unite´s)

• All other physical quantities are derivatives of

these base units

• British or US can be used




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Sensor Data Chapt1