Differentiate Between Stress And Strain Engineering Essay
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Published: Mon, 5 Dec 2016
When stretching a material, the length changes and the strain become positive. More strain means that more stress to the object once compress. When the material is compressed, the length changes and strain becomes negative. This obeys to the law of the stresses where go together with these strains, tensile stresses being positive and compressive stresses negative.
Figure above shows the relationship between stress and stain as the stress is directly proportional to strain. There is a relationship where the force applied and the object changing in physical shape. It has revealed that the elastic behavior can be defined thru some relations with the form that the physical state changes is small in related to the original. This relationship can defined as Hooke’s Law ( F = -kx)
Pyrometer is used for measuring temperature. Discuss in details four principal techniques for the measurement of temperature. State the typical applications of different types of pyrometers
A pyrometer used to measures heat from an object which has visible in bright or radiant. Pyrometers consider as thermometers where scientists use it to define the heat and heat type given out from an object. The critical variation between a pyrometer and other types of thermometers is the radiant levels on or after the heated objects are typically far too hot for interaction. That is why pyrometers have visual scanners that measure the heat.
Four principal techniques for measurement of temperature.
IR Pyrometers for Surface Temperatures
The spectrum lies at wavelengths longer than light however shorter than microwaves or measuring system. IR pyrometers usually operate with wavelengths from two to twenty microns, reckoning on the material being measured. Planck’s law states that the emissive power of a black body contains a spectral distribution reliant on the body temperature. This can be a well-known matter, thus there are numerous strategies to avoid this matter with variable target emissivity.
IR Gas Temperature Pyrometers
IR pyrometer functional at a wavelength consistent to the combustion emitted products, such as CO2 gas radiation (at 4.26 or 4.5 microns) can measure average gas temperature. This method needs gas to be combusted, meanwhile air not having a sturdy IR emission peaks. All fossil fuels produce CO2 after when it burnt, so this method is appropriate to oil and propane fired furnaces, but not for electrically heated furnaces. The temperature of the gas stately is the radiation temperature of the CO2 gases in the field of view of the lens, so choice of lens and placement is significant. 2 IR pyrometers must be located on opposite sides of the furnace to portion this temperature inhomogeneity. Whatever that blocks the assessment of the lens (as soot or dust), air penetration (less CO2 to measure temperatures) or huge differences in gas temperature with time can create the average temperature signal too strident to use straight in a control system.
Acoustic pyrometers is a method where used to measure the temperature of gases created on the temperature reliance of the speed of sound. The speed of sound diverges through the square root of the total gas temperature. This method stretches an average temperature completed an identified path length if the gas composition is identified and continuous. Guileless acoustical pyrometry uses the time of flight statistics for the leading wave front to reach the receiver. This is suitable on behalf of an average gas temperature for one path. The wavelengths may exist to be enormous, for instance, presumptuous a sound velocity of 880 m/s at a frequency of 500 Hz stretches a wavelength of 1.8 m. Ruptures of air can remain the basis of sound, giving an informal to connect, low-maintenance instrument. Numerous paths can be selected, which can be examined to provide 2D isothermal maps of furnace temperature problematic to crop by other resources for gas temperatures of 1650°C. Advantages of acoustical pyrometry embrace modest and rough equipment for industrial environments, numerous paths subsequently a single transmitter for a least amount of holes in the furnace walls for 2D temperature mapping, low operating costs and proven technology.
Suction pyrometers are a method where suction is used to appeal the hot combustion gases past a thermocouple at a great velocity to decrease the fault in gas temperature measurements. Radiation shields reduce the thermal effects of radiation. Suction pyrometers are still the best industrial apparatuses for measuring combustion gas temperatures, for instance, they are used for impermanent gas temperature measurements at a specific position or for calibration of other temperature measurement apparatus. The micro suction pyrometer has been established to evade countless of the disadvantages of the suction pyrometer. Main disadvantages with micro suction pyrometers comprise their lesser accurateness and additional brittle construction comparative to conservative suction pyrometers.
Types of pyrometers
The broadband pyrometer is used to record the broadband wavelengths of radiation, typically about 0.3 microns. However furthermost repeatedly used, they can have big mistakes in readings. Subsequently they are merely registering a minor quantity of an object heat. Everything from water vapor to dust can produce a reading error.
An optical pyrometer let a scientist to observe heat though all pyrometers are optical in the sense they can recite an object’s heat from a distance. An optical pyrometer is used to measures the heat infrared wavelengths and straight displays the manipulator the object heat distribution. Additional pyrometers typically have a screen to shows the results of an optical scan. An optical pyrometer can act lie a telescope where the scientists can look over a lens and see the infrared wavelengths of an object. Optical pyrometers are one of the oldest pyrometer types and are able to see the wavelength levels up to 0.65 microns.
A radiation pyrometer is used to determine pure radiation wavelengths. The device contains an optical scanner that can perceive 0.7 to 20 microns on the range of wavelength, the overall range for radioactive heat. The optical scanner lightens the burden of scientists in measuring the radiation levels without putting the pyrometer up to the object, where it can endanger the person in charge to expose to radiation.
Draw the functional block diagram of Electrocardiography (ECG) machines and explain each in details. From the functional block diagram, answer the following:
1. What (electrically) is being measured?
2. How is the electrical signal capture? What is the sensor? How does it work?
Draw a complete circuit to represent the functional block diagram
What is ECG?
An electrocardiogram or ECG is used to measure and analyzed electrical recording of the heart and even used to investigate heart disease. British physiologist Augustus D. Waller is the creator of electrocardiography and published the first human electrocardiogram in the year 1887. Dutch physiologist Willem Einthoven, who transformed this inquisitive physiologic phenomenon into a crucial clinical recording device, was awarded a Nobel prize in medicine.
Block diagram of ECG
When the heart depolarizes, it’s suitable (and quite precise) to denote the electrical activity as a dipole which a vector between two point charges. A vector has both a size (magnitude), and a direction. The potential diverges around the volume conductor. This applies to all intra-cardiac events, so the vector (or axis) for P waves, the QRS complex, T waves, and so on.
The electrocardiogram, or ECG is a surface measurement of the electrical potential produced by electrical action in cardiac tissue. Current flow in ion form and signals shrinkage of cardiac muscle fibers foremost to the heart’s pumping activity. The human heart can also be considered as a large muscle where the beating is just contraction of muscles. Consequently contractions of the heart create a potential. The measurement of the potential created by cardiac muscle is called as electrocardiology.
Types of electric is being measured
a) Bipolar leads: The position point located on one limb, the `sensing’ electrode can be on another limb. The leads are mark as I, II, and III.
b) Unipolar leads: The position point located in some leads that joined together, and the sensing lead is located on one limb. These leads are predictably increased, in that the position lead on the limb sensed is disconnected from the other two.
c) The V leads : The position where lengthen across the precordium, V1 in the fourth right interspace, V2 4th left, V4 at the apex (5th interspace, midclavicular line), V3 halfway in between V2 and V4, and V5 & V6 in the 5th interspace at the anterior and mid axillary lines correspondingly.
These electrode leads are usually connected to potential differences devices between selected electrodes to create the specific ECG tracings. Majority of the ECG leads are bipolar leads (e.g., standard limb leads) that apply a single positive and a single negative electrode amongst which electrical potentials are measured. Unipolar leads (augmented leads and chest leads) consist os single positive recording electrode and apply a blend of the other electrodes to assist as a merged negative electrode. Typically, once an ECG is recorded, all leads are recorded instantaneously, normally called as 12-lead ECG.
How is the electrical signal capture? What is the sensor? How does it work?
Cardiac electrical potential wave forms (voltages created through the heart as its chambers contract) are measured by the PASCO CI-6539A EKG (Electrocardiogram) Sensor. The sensor contains of the electronics box by a cable for connecting to the PASCO computer interface through a five pin DIN analog connector. 3 electrode leads pass in the electronics box on the side opposite the cable that assigns to the interface. The sensor signal is conveyed from side to side an opto-isloation circuit. An isolation transformer is used to transfer the sensor’s power.
Explain in detail idea of industrial voltage to frequency converters and frequency to voltage converters using an operational amplifier.
Voltage to frequency converter
The voltage-to-frequency converter is a converter which delivers an output frequency precisely relative to its input voltage. The digital open-collector frequency output is well-matched through all mutual logic families. Its adding input features give the VFC32 outstanding noise resistance and small nonlinearity. Complete output frequency is determined by an exterior capacitor and resistor.
Open-collector logic output is gain from the frequency output terminal. A pull-up resistor is typically connected to a 5V logic supply to generate normal logic-level pulses. Though, it connected to some power supply (+VCC). Production pulses obligate a continuous period and positive-going throughout the oneshot period. Current flowing in the open-collector output transistor proceeds by the common terminal. The terminal must be linked to logic ground.
Frequency to voltage conversion
The capacitive-coupled response network C3, R6 and R7 let typical 5V logic levels to activate the comparator input. The comparator causes the one-shot on the dropping control of the frequency input pulses. Beginning voltage of the comparator is about -0.7V. 5V logic levels having less waveform for frequency input, the comparator is activated by regulating the voltage divider of R6/R7 to a lower voltage. C2 smoothens the output voltage waveform. Greater values of C2 decrease the wrinkle in the output voltage. Lesser values of C2 let the output voltage to resolve quicker in response to a modification in input frequency. Resistor R1 can be pared to attain the preferred output voltage at the complete input frequency. The signal response current is equivalent to VIN/R1. This current is combined by response op amp and C2, creating a descending ramping integrator output voltage. Once the integrator output slopes to the verge of the comparator, the one-shot is activated. The 1mA reference current is swapped to the integrator input throughout the one-shot length, producing the integrator production ramp rising. Subsequently the one-shot period, the integrator again ramps descending. The fluctuation procedure forces a long-term stability of charge (or average current) between the input signal current and the reference current.
Describe the purpose and basic operation principle of differential pressure flow meters. Differentiate between orifice plate, venturi, nozzle and pitot tube.
Differential pressure flow meters
It is the control of fluid flow rate by interpretation the pressure loss thru a pipe restriction is possibly the greatest where usually used flow measurement method in industrialized uses (Figure 2-1). The descent of pressure created by a extensive variability of geometrical restrictions have been well considered over the years. These primary or “head” flow elements originate in a extensive diversity of configurations, all with exact application assets and flaws. Differences on the refrain of differential pressure (d/p) flow measurement
In clean liquid, gas, and steam service, orifice plates are generally used. It is obtainable for entirely pipe sizes, very economical for gauging flows in bigger pipes (over 6″ diameter). Numerous standards organizations permitted the orifice plates as is used for the supervision the transfer of liquids and gases. The orifice flow calculations used today still fluctuate from each other, though the numerous standards organizations are operational to accept a solitary, generally accepted orifice flow calculation. User can select the flow equation thru orifice sizing program. Even though it is a modest device, the orifice plate can be considered as a precision instrument. Orifice plates are fairly sensitive to a change of error-inducing situations. Precision in the drag controls, the excellence of the connection, and the state of the plate itself regulate the routine. Installation influences embrace tap position and state, form of the process pipe, capability of straight pipe innings, gasket intrusion, misalignment of pipe and orifice drags, and lead line design. Other adverse conditions comprise the corrosion or erosion of the pipes, dirt, and grease or secondary phase deposits on either orifice surface.
The venturi tubes is quite expensive, so they are mainly used for greater flows or on further tough or difficult flow applications. Venturis are not sensitive to velocity outline properties and consequently need fewer straight pipe run than an orifice. The character of scrubbing act of the flow through the tube creates the device resistant to corrosion, erosion, and interior scale build up. Due to high initial cost, the owner still is promising as the savings in fitting and functioning and maintenance costs. Flow element is long which considered by a narrowing inlet and a deviating outlet. The entrance is used to determine the inlet pressure, while the throat section is to measure the static pressure. The pressure taps nourish into a joint annular chamber, as long as an average pressure analysis over the whole perimeter of the element. The venturi is partial in its use to clean, non-corrosive liquids and gases. The great instability and the absence of holes in which material can gather create flow tubes well suitable for slurry and mud services. But, maintenance costs can be high if air removal can’t stop persisting of the pressure taps and lead lines. Plunger-like devices (vent cleaners) can be connected to occasionally eliminate accumulation from interior openings, even though the meter is online.
The flow nozzle can be said it is more stable than the orifice plate, mainly in greater or higher temperature and higher velocity services as compared to orifice plates. It used to determine high flow rates of superheated vapor. The flow nozzle also having a better flow capacity than the orifice plate and needs a lesser first investment than a venturi tube, but also delivers lesser pressure recovery. A main disadvantage of the nozzle is that it is harder to change than the orifice except it can be detached as part of a spool unit. Flow nozzles preserve their accuracy for long periods, even in tough service. Flow nozzles can be very accurate way to determine gas flows. As soon as the gas velocity influences the speed of sound in the throat, the velocity can’t surge any more and a overcome flow condition is extended.
Pitot tube is one of the simple in design flow sensors where it is used to measure varied range of flow measurement applications. Normally, it is used in air speed in racing cars and air force fighter jets. Pitot tubes also used to analyze air flow in pipes, ducts, and stacks, and liquid flow in pipes, weirs, and open channels in industrial applications. The accuracy and range capability are moderately low, while pitot tubes are modest, dependable, low-cost, and suitable for a diversity of environmental situations, plus tremendously high temperatures and a wide range of pressures.
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