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A network facing coverage problems has bad RxLev. RxQual can be bad at the same time. Sometimes the RxLev can look OK on the street (i.e. from drivetest) but coverage inside the buildings can be po...
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ICPC11 Sensors and Transducers Assignment- II 1. Four strain strain gauges gauges are bonded bonded onto onto a cantilever cantilever as shown shown in fig fig (a). Given that that the gauges gauges are placed halfway along the cantilever and the cantilever is subjected to a downward force of 0.5 N use the data given below to calculate the resistance of each strain gauge. Cantilever Data !ength l " #5c$ %idth w " & c$ *hic+ness t " ,$$ -oungs $odulus / " 01023a
Strain gauge data Gauge factor G " #.1 'nstrained resistance 0 " 1#0
Fig (a) #. Four strain strain gauges gauges with specifica specification tion given given below below are available available to $easure $easure the tor4ue tor4ue on a cylindrical shaft c$ in dia$eter connecting co nnecting a $otor and load. (a) 6raw clearly clearly labeled labeled diagra$ diagra$ss showing7 showing7 (i) *he *he ar arrang range$ e$en entt of of the the gaug gauges es on the the sha shafft (ii) (ii) *he *he arran arrange$ ge$en entt of the the gauge gaugess in the the bridg bridgee circui circuit t for for opti$ opti$u$ u$ accu accura racy cy and sensitivity. (b) 8alcul 8alculate ate the $a9i$u $a9i$u$ $ achieva achievable ble bridge bridge out:of out:of:ba :balan lance ce voltag voltagee for an applie applied d tor4ue * of 10, N$ given the following7 *ensile and co$pressive strains " ; * < =>a , where > " 1.11011 N$:# is the shear $odulus of the shaft $aterial and a is the radius of the shaft in $eters. >train gauge data7 esistance " 1#0 Gauge factor " #.1 ?a9i$u$ current " 50$@. ,. @ load load cell consis consists ts of a do$ed do$ed vertical vertical steel steel cylinder cylinder #0 c$ high high and 15 c$ in dia$eter dia$eter..
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Four flat surfaces at right angles to each other are cut on the vertical surface so as to for$ 10 c$ s4uares. esistance strain gauges are attached to these flat surfaces so that two gauges (on opposite faces) suffer longitudinal co$pression and two gauges (on the other pair of opposite faces) suffer transverse tension. *he strain gauges have the following specification7 esistance " 100 Gauge factor " #.1 ?a9i$u$ gauge current " ,0$@ *he gauges are connected in a te$perature co$pensated bridge and the out:of:balance signal is input to a differential a$plifier. 8alculate the $ini$u$ a$plifier gain if the a$plifier output voltage is to be 1 A for a co$pressive force of 105 N. -oungs $odulus for steel " #.11011 N$:# 3oissons ratio for steel " 0.#2
. @ variable dielectric capacitive displace$ent sensor consists of two s4uare $etal plates side 5 c$ separated by a gap of 1 $$. @ sheet of dielectric $aterial 1 $$ thic+ and the sa$e area as the plates can be slid between the$ as shown in fig (b). Given that the dielectric constant of air is 1 and that of the dielectric $aterial calculate the capacitance of the sensor when the input displace$ent 9 " 0.0 #.5 5.0 c$.
5.
@ variable reluctance sensor consists of a core variable air gap and an ar$ature. *he core is a steel rod of dia$eter 1 c$ relative per$eability 100 bent to for$ a se$i:circle of dia$eter c$. @ coil of 500 c$ turns is wound onto the core. *he ar$ature is a steel plate of thic+ness 0.5 c$ and relative per$eability 100. @ssu$ing the relative per$eability of air " 1.0 and the per$eability of free space " =10:B$:1 calculate the inductance of the sensor for air gaps of 1 $$ and , $$. &. Cy ta+ing a central flu9 path esti$ate the inductance of the sensor shown in fig.(e) (a) For Dero air gap (b) For a #$$ air gap. @ssu$e the relative per$eability of core and ar$ature is 10 and that of air is unity.
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(e) . Fig. (f) >hows a variable reluctance force sensor which is incorporated into the bridge circuit of Fig. (g) %hen the applied force is Dero the ar$ature is positioned along the center line @C. (a) /9plain why the sensor would be suitable for $easuring force signals containing fre4uencies between 0 and 10 BD. (b) >+etch the fre4uency spectru$ of the bridge output voltage. (c) 'se the data given to calculate the for$ of the bridge output voltage when F " E1.0N and F " :1.0N (d) 'sing the results of (c) e9plain how to de$odulate the bridge output voltage. Data: verall spring stiffness " 10, N$:1 /ffective $ass of spring and ar$ature " #510:,+g. 6a$ping ratio " 0. nductance of each coil " #0< (1E#d ) $B (d = air gap in $$) @$plitude of bridge supply " 1 A Fre4uency of bridge supply " 1000 BD.
Fig(f)
Fig(g)
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H. @ pieDoelectric crystal acting as a force sensor is connected by a short cable of negligible capacitance and resistance to a voltage detector of infinite bandwidth and purely resistive i$pedance of 10 ?. (a) 'se the crystal data below to calculate the syste$ transfer function and to s+etch the appro9i$ate fre4uency response characteristics of the syste$. (b) *he ti$e variation in the thrust of an engine is a s4uare wave of period 10 $s. /9plain carefully but without perfor$ing detailed calculations. %hy the above syste$ is unsuitable for the application. (c) @ charge a$plifier with feedbac+ capacitance 8f " 1000 pF and feedbac+ resistance f " 100? is incorporated into the syste$. Cy s+etching the fre4uency response characteristics of the $odified syste$ e9plain why it is suitable for the application of part (b). Crystal data: 8harging sensitivity of force " # p8N:1. 8apacitance " 100pF Natural fre4uency " , +BD 6a$ping atio " 0.01 2. (a) *he casing of a co$pressor is e9ecuting sinusoidal vibrations with a displace$ent a$plitude of 10:$ and fre4uency 500 BD. 8alculate the a$plitude of the acceleration of the casing in units of gIg " 2.H1 $s:#J (b) @ pieDoelectric crystal accelero$eter has a steady:state sensitivity of #.0 p8
R0
∆ R R
for the conditions listed below.
S g
ε ( µ m < m )
(i) 1#0 #.0# 1&00 (ii) ,50 ,. &50 (iii ) ,50 #.0 &50 (iv) 1000 #.0& #00 (b) For the conditions described above deter$ine the output voltage A0 for an initially balanced bridge if the input voltage Ai is
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(i) #A (ii) A (iii) A (iv) 10A (c) %hat happens if Ai is increased to 50A to i$prove the output A0 . (d) For the gauges specified in (a) $onitored in a single ar$ %heatstone bridge with Ai " 5A deter$ine the strain ε if the output voltage A0 is (i) 1.5 $A (ii) ,., $A (iii) .H $A and (iv) 5. $A
11. @ linear resistance potentio$eter is 50$$ long and is unifor$ly wound with a wire having a resistance of 10000L. 'nder nor$al conditions the slider is at the centre of the potentio$eter. Find the linear displace$ent when the resistance of the pot as $easured by a %heatstone bridge for two cases is 1) ,H50 L #) 5&0 L. @re the two displace$ents in the sa$e directionK f it is possible to $easure a $ini$u$ value of 10 L resistance with the above arrange$ent. Find the resolution of the potentio$eter. 1#. @ variable potentio$eter has a resistance of ML and it is e9cited with a voltage source of 10A 68 supply. *he output is connected to a load resistance of 10+L. 6eter$ine the loading errors for the wiper positions corresponding to +"i<t"00.#50.50.5 O1. plot the graph of error As i < t.
1,. @ !A6* has the following specifications. /9citation voltage is 10A at 00BD. *he $a9i$u$ output voltage is #.5A. ange of core $ove$ent is ;1.5 c$. a) 8alculate the output voltage when the core is E1 c$ away fro$ the null. >+etch the input O output wavefor$. C) >+etch the output wavefor$ when the core is $oved with a 1BD sinusoidal $otion fro$ the null. 1. @ !A6* has an output of &A r$s when the displace$ent is 0.910:,$$. 6eter$ine the sensitivity of this instru$ent in A<$$. @ 10A volt$eter with 100 scale divisions is used to read the output. *wo: tenth of a division can be esti$ated with ease. 6eter$ine the resolution of the volt$eter. *he above arrange$ent is used in pressure transducer for $easuring the deflection of a diaphrag$. *he d iaphrag$ is deflected through 0.5910: ,$$ by a pressure of 1000N<$#. 6eter$ine the sensitivity and resolution of this instru$ent.
