Que1.1. Define detector and transducer with a common illustration.
Answer Detector 1. It’s defined as an element which produces signal relating to the volume being measured. 2. It can also be defined as “ A device which provides a usable affair in response to a specified measurand. ” Transducer 1. It’s defined as an element when subordinated to some physical change gests a affiliated change or an element which converts a specified measurand into a usable affair by using a transduction principle. 2. It can also be defined as a device that converts a signal from one form of energy to another form. 1. A line of constantan amalgamation( bobby
– nickel 55- 45 amalgamation) can be called as a detector because variation in mechanical relegation( pressure or contraction) can be tasted as change in electric resistance. 2. This line becomes a transducer with applicable electrodes and input- affair medium attached to it. therefore we can say that ‘ detectors are transducers ’.
Que1.2. Explain the characteristics of detectors.
Answer stationary characteristics delicacy specified by trip or generally error It’s given by, b. Precision It describes how far a measured volume is reproducible as also how close it’s to the true value. Resolution
1. It’s defined as the lowest incremental change in the input that would produce a sensible change in the affair. This is frequently expressed as chance of the measured range( MR).
2. The measured range is defined as the difference of the maximum input and the minimal input, that is, MR = xmax – xmin.
3. For a sensible affair y, if the minimal change in x is( x) min, also the maximum resolution is minimal sensible signal( MDS)
1. Noise in a detector occurs because of numerous reasons — internal sources or oscillations due to externally generated mechanical and electromagnetic influences.
2. Noise is considered in detail, on individual graces and frequently an original noise source is considered for test purposes.
3. still, the minimal signal position that If the input doesn’t contain anynoise.produces a sensible affair from the detector is determined by its noise performance or noise characteristics.
4. For this, the original noise source is connected to the input side of the ideal quiet detector to yield an affair which is the factual affair position of the detector.
5. The MDS is also taken as the RMS original input noise. When signal exceeds this value, it’s called a sensible signal. Threshold At the zero value condition of the measurand, the lowest input change that produces a sensible affair is called the threshold. perceptivity
1. It’s the rate of the incremental affair to incremental input, i.e., g. Selectivity and particularity
1. The affair of a detector may change when tormented by environmental parameters or other variables and this may appear as an unwanted signal. The detector is also said to benon-selective. 2. It’s customary to define selectivity or particularity by considering a system of n detectors each with affair yk( k = 1, 2,., n). 3. The partial perceptivity Sjk is defined as the measure of perceptivity of the kth detector to these other snooping amounts or variables xj as 4. A selectivity matrix would therefore be attained with Sjk as the jkth entry. An immaculately picky system will have only slant entries Sjj in the selectivity matrix. 5. An immaculately specific system is characterized by having a matrix with a single entry in the slant. Following relationship describes selectivity, h. Nonlinearity Nonlinearity can, be specified in two different ways, . divagation from stylish fit straight line attained by retrogression analysis.
2. divagation from a straight line joining the end points of the scale. Hysteresis It’s the difference in the affair y of the detector for a given input x, when x reaches this value in upmarket and downscale directions. The causes are different for different types of detectors. In glamorous types, for illustration, it’s the pause in alignment of the dipoles, in semiconductor types; it’s the injection type slow traps producing the effect, and so on. Affair impedance It’s a characteristic to be considered on individual merit. It causes great restriction in interfacing, specifically in the choice of the succeeding stage. insulation and grounding
1. insulation is necessary to exclude or at least reduce undesirable electrical, glamorous , electromagnetic, and mechanical coupling among colorful corridor of the system and between the system and the terrain.
2. also, grounding is necessary to establish a common knot among different corridor of the system with respect to which eventuality of any point in the system remains constant. Dynamic characteristics
1. These involve determination of transfer function, frequence response, impulse response and step response and also evaluation of the timedependent labors. 2. The two important parameters in this connection are Fidelity determined by dynamic error. Speed of response determined by pause.
3. For determining the dynamic characteristics, different specified inputs are given to the detector and the response characteristics are studied.
4. With step input, the specifications in terms of the time constant of the detector are made.
5. Generally, the detector is a single time constant device and if this time constant is t, also one has the specifications as given
. Response time of the detectors Response time Value in terms of 6. This gives t0.9/ t0.5 = 3.32 which is taken as a quick check relation. Impulse response as well as its fourier transfigure are also considered for time sphere as well as frequence sphere studies.
Que1.3. Give the bracket of detectors.
Answer Detectors can be classified grounded on the volume being measured 1. relegation, position and propinquity detectors i. Potentiometer ii. Strain- gauged element iii. Capacitive element iv. Differential transformers Eddy current propinquity detectors vi. Inductive propinquity switch vii. optic encoders viii. Curvaceous detectors ix. propinquity switches( glamorous ) Hall effect detectors. 2. haste and stir Incremental encoder ii. Tachogenerator iii. Pyroelectric detectors. Detectors and Transducers I 1 – 6 E( EN- Sem- 5) 3. Force Strain hand cargo cell. 4. Fluid pressure Diaphragm pressure hand ii. Capsules, bellows, pressure tubes iii. Piezoelectric detectors iv. Tactile detector. 5. Liquid inflow perforation plate ii. Turbine cadence. 6. Liquid position Floats ii. Differential pressure. 7. Temperature Bimetallic strips ii. Resistance temperature sensors iii. Thermistors iv. Thermo- diodes and transistors Thermocouples vi. Light detectors vii. print diodes viii. print resistors ix. Photo transistor.
Que1.4. Classify transducers.
Answer Bracket grounded on the principle of transduction i. The transducer is classified by the transduction medium. ii. The transduction medium may be resistive, inductive or capacitive depends on the conversion process that how input transducer converts the input signal into resistance, inductance and capacitance independently. Primary and secondary transducer Primary transducer i. The transducer consists of mechanical as well as the electrical bias. ii. The mechanical bias of the transducer change the physical input amounts into a mechanical signal. This mechanical device is known as the primary transducers. Secondary transducer
i. The secondary transducer converts the mechanical signal into an electrical signal.
ii. The magnitude of the affair signal depends on the input mechanical signal. Passive and active transducer Passive transducer
i. The transducer which requires the power from an external force source is known as the unresistant transducer. ii. They’re also known as the external power transducer.
iii. The capacitive, resistive and inductive transducers are the illustration of the unresistant transducer. Active transducer
i. The transducer which doesn’t bear the external power source is known as the active transducer.
ii. similar type of transducer develops theirs owns voltage or current, hence known as a tone- generating transducer.
iii. The affair signal is attained from the physical input volume. Analog and digital transducer Analog transducer
i. The analog transducer changes the input volume into a nonstop function.
ii. The strain hand, LVDT, thermocouple and thermistor are the exemplifications of the analog transducer. Digital transducer These transducers convert an input volume into a digital signal or in the form of the palpitation. The digital signals work on high or low power. Transducer and inverse transducer Transducer The device which converts thenon-electrical volume into an electric volume is known as the transducer. Inverse transducer The transducer which converts the electric volume into a physical volume, similar type of transducers is known as the inverse transducer. The transducer has high electrical input and lownon-electrical affair.