Bullying in Early Education Essay Example | Topics and Well Written Essays - 1500 words

Bullying in Early Education - Essay Example ave equal strength or power to the bully† (Berthold & Hoover, 2000; Olweus, 1996; Solberg, Olweus & Enderson, 2007; Sourander, Holstela, Helenius & Piha, 2000). Aggression was clearly defined in Lee’s research on the relationship of aggression and bullying to social preference as a â€Å"behavior that is intended to harm someone either physically or psychologically (Berkowitz, 1993), manifests itself in a wide variety of acts† (Lee, 2009, 323). Despite differences in definitions, bullying still manifests an aggressively vicious behavior expressed either indirectly or directly by a repeated tormenting towards a victim with obviously less strength and power to defend oneself from his aggressor aimed to harm him or her physically or psychologically. III. The role of gender in bullying Diverse research literatures examined the role of gender in increased susceptibility in bullying. There are actually two sides to be examined: (1) does gender play a significant part in assuming the role of the aggressor? In this issue, one would like to assess and evaluate if indeed boys are the instigator of bullying. If so, what forms of bullying do they usually perform? On the other hand, does it necessarily follow that girls are always the victims of bullying? What other perspectives in bullying give credence to gender differences as relevant correlates of bullying? The study conducted by Carbone-Lopez, et.al. (2010) reveal that gender differences have significant impact on bullying and victimization. However, it was necessary to qualify the direct form of bullying versus the indirect form. The direct form involves behavior that aims to physically harm the victim through any of the following means: hitting, kicking, pushing (Carbone-Lopez, et.al, 2010, 333) and fighting, flicking,... Bullying in Early Education Parents of bullies were observed to resort to unjustifiable physical punishment instigated by mood swings and flares. Due to the fact that bullies have never learned the value of sharing or cooperation, getting along with others is not an ultimate priority. In this regard, the objective of the research is to determine if gender affects the way children respond to bullying in terms of the response or action taken against bullying and how young children, in general, deal with it. II. Differences in Definition of Bullying Bullying has been described by Marees & Petermann (2010) as â€Å"a specific for or aggressive behavior, namely the systematic humiliation, harassment and/or torment of certain children by their peers: (178). Taylor (2003), on the other hand, who studied primary school bullying and the issue of gender differences, defined bullying as â€Å"a subcategory of aggressive behavior; but a particularly vicious kind of aggressive behavior since it is directed, often repeated ly, towards a particular victim who is unable to defend himself or herself effectively†. The impact of gender on the response of children to bullying can still be further investigated to ensure that possible findings would shed light on the diversity of gender and the way they perceive bullying as either a threat to be directly addressed or ignored. There could be other reactions or responses that were not evidently investigated, or reported especially for the age group targeted for the project.

Barriers to Communication Essay Example | Topics and Well Written Essays - 250 words

Barriers to Communication - Essay Example Recent research has shown that many recruiters now rate communication skills as the most important characteristic sought for in job applicants during selection (Yate, 2009). In this paper, I will be illuminating on the most important barriers that must be understood in order for organizations improve on the communication skills of their people and ultimately efficiency. I will begin by defining what communication is before discussing the process through which occurs with the intention of helping all readers of the report to better utilize the communication function for better personal and organizational performance. Communication can be well defined as a method of exchanging information and common understating between individuals. Unless a mutual understanding is generated from exchange of information, communication will not take place smoothly. The most important necessities in every communication process are the sender and the recipient. The sender will usually start the communication. The recipient is that particular person for which a message is intended. Message refers to the outcome and it may take any form from verbal to nonverbal or written or Language. The flow of information between senders may be hindered by noise, which includes perceptions, barriers in form of language, emotional issues, physical interruptions and attitudes held by the different parties. Feedback occurs at the point when the receiver provides a response to the initial message by a sender. Feedback is crucial to the process of communication as it tells Communication as well as methods that can be used to better improves the daily communication. The common types of barriers that I will be addressing include language barrier- Language is a very important aspect of communication as it plays the role of mediation allowing humans to effectively understand

Enterprise Architecture Essay Example | Topics and Well Written Essays - 2500 words - 3

Enterprise Architecture - Essay Example The article provides a brief overview of the TOGAF framework, in simple and comprehensive terms. The author offers an architecture development methodology, based on TOGAF and comprising four steps: tailoring TOGAF to suit enterprise needs; defining the scope of work; overseeing development; and managing post-implementation aspects. Banerjee claims that the TOGAF architecture is not the ultimate solution but merely a starting point in the development of effective enterprise solutions. The article can be extremely useful in the study of various enterprise architecture frameworks. In this article, the TOGAF framework is the central object of analysis. The researchers assert that the main rules and principles of rule-driven systems are too old to be effective. Nonetheless, they have the potential to provide better insight into the rational structure of enterprise architecture frameworks. Bommel et al (2006) use the rules of the TOGAF network to analyze two examples and conclude that, eve n if certain formulations lead to redundancy, they should not be discarded, not to distort the EA picture. Designing enterprise architecture models is not an easy task. Compatibility of various frameworks presents another issue. In this article, the authors discuss and evaluate the TOGAF architecture framework and its relation to architecture development method. The results show how TOGAF can complement EA management and provide the basis for resolving EA related concerns. Carraro and Chong provide a detailed description of the Software as a Service model of enterprise architecture. The benefits and considerations for embracing SaaS are discussed. The article sheds light on how SaaS affects information technologies and how to become a SaaS provider. The article is an excellent source of information about SaaS and become the starting point in the analysis of SaaS applications and frameworks.

Could Christianity have benefited without Constantine Research Paper

Could Christianity have benefited without Constantine - Research Paper Example In preliminary readings, there seem to be two extreme views of Emperor Constantine who ruled the Roman Empire between 306 and 337.One school of thought asserts that Constantine was the founder of Christendom and his laws and actions laid the foundation for the institution of Christianity in the Roman Empire and throughout Europe. Another set of thinkers present Constantine as an opportunist who used Christianity to further his personal political goal of unifying and ruling the Roman Empire. In either contexts, it can be argued that Constantine played a fundamental role in the promotion of Christianity. This paper examines whether Christianity could have persisted without Constantine or not. According to Professor Stark, in the year AD40, Christians were very few and some estimates put the entire membership of the religion at around 1,0001. It was like any other religious sect and any other group in the Roman empire. However, Christianity grew at a very outstanding rate of 3.42% per a nnum and 40% per decade around AD2502. This suggests that Christianity was already growing when Constantine took over the reign of the Roman Empire in AD 306. In light of this fact, this research will proceed on the premise that Christianity would have survived and grown even without the pro-Christian policies of Constantine. The research will test this hypothesis to ascertain its truthfulness or falsity. Persecutions Before Constantine Constantine was serving in the court of Diocletian who ruled Rome from 285 – 305 AD3. ... om the eyes of Diocletian and other Romans of his generation, Christianity was a foreign religion that had its roots in Ancient Israel, then known to the Romans as Palestine. Due to this, the Romans could not take the criticisms in good faith and make adjustments to their beliefs. Rather, Diocletian and his government felt compelled to take action against the Christian critics of the Roman pagan religious system. Diocletian and his government launched the Great Persecution which was the last and the most severe Roman persecution of the Early Christians5. In the national context, Christianity was illegal in the Roman Empire in Diocletian's era. This was the official position and most people in the Roman Empire saw it as a secret society and looked at the members with a high degree of skepticism and suspicion6. Christianity was neither Roman nor Barbarian; it was just some kind of foreign religion that posed a threat to the Roman culture7. More significantly, Christianity in the time o f Diocletian was expanding. This created an urgent need to control the expansion of Christianity. On February 23, 303, Diocletian destroyed the Church in Nicomeda and burnt scriptures and confiscated the Church's assets and treasures8. This sent a clear message that Diocletian was against the expansion and growth of the Christian Church. He was obviously not ready to tolerate the Christian Church as a competitor to traditional Roman customs and practices. On the same day, Diocletian issued an edict against Christians which prohibited Christian worship in the Roman Empire9. Three more edicts were issued by Diocletian and these were meant to ban the practice of Christianity and prevent Christians from carrying out their activities, which he thought were detrimental to the Empire and against

Federal Contracts Essay Example | Topics and Well Written Essays - 750 words

Federal Contracts - Essay Example This move is extremely essential for small entrepreneurs to expand their businesses. This paper analyzes the federal act support for small businesspersons with the aim of expanding their businesses. It further provides an organizational chart that supports working with the federal contracting system. Federal Contracts under a given Business Development Program Federal government only provides support to businesspersons or prime contractors that are performing at least one active EPA contract. In addition, they must also be eligible for the award of federal contracts. The other parties who are bound to receive assistance are companies whose corporate policy is to promote, develop and implement subcontracting opportunities for the sector of socioeconomic. In order to help such small businesses that are still starting, but have a viable idea; the SBA came up with the 8(a) Business Development Program. What is the 8(a) Business Development Program? Business Development Program is assista nce program for small-disadvantaged businesspersons with bigger ideas. This program also offers a broad scope of assistance to firms under people who are economically disadvantaged. ... Business Development Program Benefits The Business Development Program assists inspiring entrepreneurs greatly since participants being able to receive sole-source contracts of roughly $4 million for goods and services. Concerning manufacturing, the participants receive a total of $6.5 million, which is to assist in establishment and expansion of already existing business. Additionally, as much as this program helps, 8(a) still assists in building of competitive advantage. This program also helps in the improvement of institutional expertise by assisting participants to take part in competitive acquisitions (Ralph & John, 1995). Firms under 8(a) program are capable of forming joint ventures that assist them in teaming up to bid contracts. This process enhances the ability of most firms to perform larger prime contracts and overcome the effects of contract bundling. It is also possible for such companies to combine and form one large contract as highlighted in the Mentor Protege Progr am. There are usually the requirements and the objectives of the 8(a) Business Development Program, which involves graduation of firms to higher notch of competitive advantage. This process assures organizations of thriving in competitive business environment. The goal of this program is to help firms maintain balance between their commercial and government businesses. As stipulated in the NAICS code, it also provides the limit on the amount of dollar value of sole-source contracts that individual participant is likely to receive while taking part in the program, which is roughly $100 million. The requirements include the following: a) Systematic evaluations b) Yearly reviews c) Business planning

Healthy Lifestyle Essay Example for Free

Healthy Lifestyle Essay Regular exercise is essential for good health. It tones the muscles, strengthens the bones and makes the heart and lungs work better. Exercise also helps to relieve stress. The most beneficial type of exercise is aerobics. Aerobic exercises, in the form of jogging, cycling and lap swimming, strengthens the heart. It is important to choose a form of exercise that we enjoy. It could be dancing or just walking. As long as we do it regularly, we will be fit. People who are fit enjoy life more because they can join in any kind of activity. To maintain a healthy life, it is necessary to develop good diet habits. Balance your choices of food. It is not that we have to give up our favourite food. We just have to be smart about how often and how much of it we eat. Our body needs nutrients like proteins, carbohydrates, fats, vitamins and minerals. Balancing food choices will help us get all these nutrients. Avoid eating junk food or processed food which is high in sugar or salt content. Developing good health habits are important if we want to keep healthy. Don’t smoke, avoid excessive alcohol intake and keep moderate hours. Go to bed early and wake up early. Work hard and play hard too. Have a positive attitude towards people and work. Half-yearly dental check-ups are also necessary to maintain dental health. Being overweight can lead to a lot of health problems. We can suffer from heart disease, high blood pressure and so on. Weight control requires conscious effort and self control. Diet and exercise play the most important role in weight control. Make sure exercise is part of our daily programme. Watch the amount and type of food we eat. Health is pleasurable; ill health is miserable. There are other threats to health but if we remember the points mentioned above, we should enjoy good health.

Step by step design of a lock

Step by step design of a lock Introduction This paper outlines the step by step design of a lock in amplifier based micro-ohmmeter. This is very useful in measuring small resistances without applying large currents. And find its usefulness in tracing short circuits on printed boards containing sensitive components. The Audio Micro Ohm Meter uses synchronous detection to measure low value resistances. The circuit provides a variable frequency audio tone to indicate the resistance under test. Such a tone is invaluable when troubleshooting shorted tracks on multi-layer circuit boards because it is easier and quicker to observe 1. The source generates a 1KHz, 250mV peak square wave carrier signal that is injected into the unknown resistance, the resulting voltage across the resistor is amplified by the instrumentation amplifier. The phase reversing switch then rectifies the complementary square wave input, the rectified output is not all smooth so a low pass filter is needed. A Voltage controlled is then used to measure and indicate low value resistances such as track resistances on printed circuit boards. To provide a convenient indication, we want a ‘display that has high resolution (like a digital display) but is easy to read (like analogue meter) and that preferably doesnt even need to be looked at, so we can concentrate on the probes. To trace short circuits, the one thing we dont really need is high accuracy, since we are generally moving the probes 1. A muting detector then comes in to compare the control voltage with reference voltage. The Proteus ISIS software is used for the simulation of the circuit while a printed circuit board was used for the verification of the circuit. Resistor selection, analysis of waveforms , sensitivity and linearity of the device to supply voltage and possible improvements of the device were discussed. Excitation Oscillator One of the most useful ICs ever made is the 8-pin 555 timer and it is used in many projects. It can be used to build many circuits by just adding a few external components. NE555 is a popular version and it is suitable in most cases where a 555 timer is specified. Some low power types of the 555 are made, for instance the ICM7555, but can only be used when specified (to increase battery life) because their maximum output current of about 20mA (with a 9V supply) is too low for many standard 555 circuits. The ICM7555 has the same pin arrangement as a standard 555. The circuit symbol for a 555 is a box with the pins arranged to suit the circuit diagram: for example 555 pin 8 at the top for the +Vs supply, 555 pin 3 output on the right. Usually just the pin numbers are used and they are not labeled with their function. Standard 555 ICs create a significant glitch on the supply when their output changes state. This is not a problem in small circuits with no other ICs, but in a complex circuit a smoothing capacitor can be connected across the +Vs and 0V supply near the 555 . The 555 timer operates in different modes. The astable mode suits our design criteria. An astable circuit produces a square wave, this is a digital waveform with sharp transitions between low (0V) and high (+5Vs). It is possible that the durations of the low and high states may be different. The circuit is called an astable because it is not stable in any state: the output is continually changing between low and high. Our circuit needs a square waveform output of 4KHz, for this to be obtained an appropriate resistor value can be estimated by calculation to obtain the needed signal to drive the circuit Duty cycle The duty cycle of an astable circuit is the proportion of the complete cycle for which the output is high (the mark time). It is usually given as a percentage. The duty cycle of our circuit can be determined using Time period. The timeperiod (T) of the square wave is the time for one complete cycle, but it is usually better to consider frequency (f) which is the number of cycles per second 2. The time period can be split into two parts: T = Tm + Ts 5 Mark time (output high): Tm = 0.7 Ãâ€" (R1 + R2) Ãâ€" C1 Space time (output low): Ts = 0.7 Ãâ€" R2 Ãâ€" C1 we can determine our R2 using C3= 10nF, R1=1k and f= 4kHz we calculate our R2 as Tm = 0.7 X (1K + 33K) X 10 X 10^-9 = 238 ÃŽ ¼s While Space-time represents low output, Ts= 0.7 Ãâ€" R2 Ãâ€" C1 Ts = 0.7 X (1K) X 10 X 10^-9 = 0.7 ÃŽ ¼s T = Tm + Ts = 238 + 0.7 = 238.7 ÃŽ ¼s Duty cycle = = 99.7% The Quadrature Divider A quadrature divider, comprises a plurality of flip-flops, it includes at least two flip-flop, the flip-flops are interoperably coupled in series to produce a set dividing ratio 7. Each of the flip-flops includes two differential inputs I, two differential outputs O, and two differential clock inputs C, the outputs O, of one flip-flop is connected to the inputs I, of the next flip-flop, the outputs O, of the last flip-flop is connected inversely to the inputs I, of the first flip-flop, the flip-flops are clocked at their clock inputs C with differential clock signals in a consecutive manner which, for each flip-flop, are individually selected from quadrature clock input signals, 0, 90, 180, and 270, the quadrature divider is an even number divide-by-n circuit comprising a number of 2n flip-flops and providing a number of 4n output signals having 4n equidistant phases. 9 In our case the quadrature divider receives the square waveform signal from excitation oscillator as its clock signal . Figure 4 and 5 of the appendix show the pictorial representation of the quadrature divider as obtained from the circuit simulation and the oscilloscope graphic display. There are four output signals from the quadrature divider and they each have amplitude of about 5V but frequency of 1 KHz. This shows that the quadrature divider effectively divides the clock frequency into four amongst the equidistant phases. Attenuator An attenuator is a circuit that allows a known source of power to be reduced by a known factor usually expressed in decibels. The main advantage of an attenuator is that it is made from non-inductive resistors and therefore able to change a source or load, which might be reactive, into a resistive one that is know. The power reduction is achieved by the attenuator without introducing distortion. The attenuator used in our circuit is a pi type It is used to attenuate the 0 and 180 degrees antiphase 5V signal form the quadrature divider to 250mV at 1KHz. In order to get this value we need to select R5 in this attenuator circuit. Using Thevenins theorem. RTH = R5// (R3 + R4) where RTH = 100 ohms, R3 = 1K1ohms and R4 = 1K1 ohms. R5 = = 104.76 ohms. The best resistor to this to this value is a110 ohms resistor. So R5 = 110 ohms. figure 6 of the Appendix shows the graphical output of the attenuator with amplitude of about 250mV and frequency of 1 KHz. The attenuators gain in decibels is obtained by finding the ratio of the voltage corresponding to a known factor. Using the formula: , where R1 = 1100 ohms and the Z = 100, K = = 1.2 The value of attenuation, A in dB is obtained using K = 10 (A / 20) 1.2 = 10 (A / 20) A = 20 log 1.2 = 1.584 dB Instrumentation Amplifier An instrumentation amplifier is a variation of differential amplifier with input buffers that eliminates the need for input impedance matching making the amplifier suitable for use in measurement 5. It is a differential op-amp circuit providing high input impedances with the pleasure of gain adjustment through the adjustment of a single resistor. Instrumentation amplifier has very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection ratio, and very high input impedances. The instrumentation amplifier used in this circuit affected its accuracy and stability. The attenuated signal is applied across a resistor with very small resistance. The voltage drop across the resistor is small and needs to be amplified. The instrumentation amplifier does this, it composes of three op-amps arranged so that there is one op-amp to buffer each input signal and one to produce the desired output with adequate impedance matching for the function.3 The gain of the instrumentation amplifier circuit used for this micro-ohmmeter design is known to be 60 dB. Using the formula below then, Av =where AV = 60 dB, R = 10 k, 60 =, R9 = = 338.98 ÃŽ © The best resistor to this value is 340 ÃŽ © and it controls the gain of the instrumentation amplifier. The negative feedback of U3:A makes the voltage at pin 2 of U3:A to be equal to Voltage across R8. while, the voltage at pin 6 of U3:B is held to a value equal to Voltage across R14. This establishes a voltage drop across R9 equivalent to the voltage difference between V1 and V2 and subsequently a current through R9 and since no current is drawn by the feedback loops of the two input op-amps , the same amount of current through R9 must be going through R10 and R12 resistors above and below it. This produces a voltage drop between points A and B equal to V The ordinary differential amplifier part of the circuit then amplifies this voltage drop by a gain of 1. The post- differential amplifier circuit, with gain = R19 / R15 and differential input resistance = 2*R15. The two amplifiers on the left are the buffers. With R9 = Rgain removed (open circuited), they are simple unity gain buffers; the circuit will work in that state, with gain simply equal to R19 / R15 and high input impedance because of the buffers. The buffer gain is increased by putting resistors between the buffer inverting inputs and ground to shunt away some of the negative feedback; however, the single resistor Rgain between the two inverting inputs is a much more elegant method: it increases the differential-mode gain of the buffer pair while leaving the common-mode gain equal to 1. This increases the common-mode rejection ratio (CMRR) of the circuit and enables the buffers to handle much larger common-mode signals without clipping than would be the case if they were sep arate and had the same gain. Another benefit of the method is that it boosts the gain using a single resistor rather than a pair, thus avoiding a resistor-matching problem. The ideal common-mode gain of an instrumentation amplifier is zero. The common-mode gain of the instrumentation amplifier used in this design is near zero because of the equally numbered resistors and by the matched common-mode gains of the two buffer op-amps of the instrumentation amplifier. To obtain a closely matched resistors is difficult, as is optimizing the common mode performance of the input op-amps. All resistors are of equal value for this instrumentation amplifier except for R9. This method has the advantage of possessing extremely high input impedances on the input voltage across R=39 because they connect straight into the non-inverting inputs of their respective op-amps and adjustable gain that can be set by a single resistor. The lowest gain possible is obtained from the above circuit with R9 completely open (infinite resistance), and that gain value is 1. The output of the instrumentation amplifier is an anti-phase square wave signal from the that connects to the phase shift detector for further modification. Lock-In Amplifier A lock-inamplifier otherwise known as a phase-sensitive detector is a type of amplifier that can extract a signal with a known carrier wave from extremely noisy environment. It is a homodyne with a very low pass filter making it very narrow band. Lock-in amplifiers utilizes mixing, via a frequency mixer, to convert the signals amplitude and phase to a DC—in fact a time-varying low-frequency—voltage signal. It is often used to measure phase shift, even when the signals are of a high value and of high signal-to-noise ratio, and do not need any other improvement.To obtain signal at low signal-to-noise ratios, it is necessary that a strong, undiluted reference signal is made available at the same frequency as the signal to be measured. Phase Difference Two oscillators that have the same frequency and different phases that is, a phase difference, the oscillators are said to be out of phase with each other. The amount by which such oscillators are out of step with each other can be expressed in radians from 0 to 2Ï€ or in degrees from 0 ° to 360 °, If the phase difference is 180 degrees (Ï€ radians), then the two oscillators are said to be in antiphase. If two interacting waves meet at a point where they are in antiphase, then destructive interference will occur. It is common for waves of electromagnetic (light, RF), acoustic (sound) or other energy to become superposed in their transmission medium. When that happens, the phase difference determines whether they reinforce or weaken each other. Complete cancellation is possible for waves with equal amplitudes. Phase compensation This is the correction of phase error (i.e., the difference between the actually needed phase and the obtained phase). To obtain stability in an operational amplifier a phase compensation is required. To keep a phase margin in the phase compensation a capacitor/RC network is usually used . A phase compensator works by subtracting out an amount of phase shift from a signal which is equal to the amount of phase shift added by switching some additional amplifier stages into the amplification signal path. Low-Pass Filter A low-pass filter is a filter that passes low-frequency signals but attenuates (reduces the amplitude of) signals with frequencies higher than the cutoff frequency. An ideal low-pass filter completely eliminates all frequencies above the cutoff frequency while passing those below unchanged: its frequency response is a rectangular function, and is a brick-wall filter 8. If we need to get rid of an interfering signal in order to get a lot of attenuation, several RC filters can be cascaded. Unfortunately, the impedance of one RC section affects the next. What this means is that the transition between the pass and stop bands will not be sharp. A sharp transition helps reduce the interfering signal without causing degradation to the desired signals. In this case, the Sallen-Key active filter can do the job well. This circuit uses a 2-pole filter. Cascading a number of stages can give a steep attenuation transition with a very sharp knee. This cut-off frequency aids in selecting the R20 an d R22 resistor values to be used in the low pass filter design to average noise in the DC signal 6. The required Q for the butterworth filter = 1.414. The op-amp stage is a unity gain follower when R20 = R22. if C9 and C10 are equal, then the Q = 1.5858 for Butterworth response. Using convenient near values gain of 1.56 in the formula, R20 = R22 = Q / (4 ·Ãâ‚¬Ã‚ ·fo ·C9) where, fo = cut-off frequency = 4Hz, C9 = C10 = 0.1ÃŽ ¼F R20 = R20 = 310.31kÃŽ © The nearest standard resistor value to this calcualted resistor value is 330k Voltage Controlled Oscillator A voltage-controlled oscillator is an oscillator whose frequency is determined by a control voltage. As the control voltage causes the frequency to rise slowly until it hits a maximum and then falls back to the starting frequency. The first op-amp is an integrator(U7:A). A voltage divider puts the + input at half the control voltage. The op-amp attempts to keep its input at the same voltage, which requires a current flow across the 100k to ensure that its voltage drop is half the control voltage. When the MOSFET at the bottom is on, the current from the 200k goes through the MOSFET. Since the 100k resistor has the same voltage drop as the 100k but half the resistance, it must have twice as much current flowing through it. The additional current comes from the capacitor, charging it, so the first op-amp must provide a steadily rising output voltage to source this current. When the MOSFET at the bottom is off, the current from the 200k goes through the capacitor, discharging it, so a steadily falling output voltage is needed from the first op-amp. The result of the operation of this integrator circuit is a triangular waveform confirmed by figure 13 of the appendix. The capacitance of the capacitor in our circuit is determined thus: The second op-amp is a Schmitt trigger. It takes the triangle wave as input. When the input voltage rises above the threshold of 3.33 V, it outputs 5 V and the threshold voltage falls to 1.67 V. When the input voltage falls below that, the output goes to 0 V and the threshold moves back up. The output is a square wave. Its connected to the MOSFET, causing the integrator to raise or lower its output voltage as needed 4. Figure 14 shows the graphical representation of this circuit . The variation of the supply voltage from 3V to 9V while observing the output signal frequency obtains the sensitivity of the overall voltage- controlled oscillator circuit to supply voltage. From the test observation, the VCO produced no output signal at 3Vand beyond 6.2V. The below table shows the values obtained for the during the sensitivity test of the voltage-controlled oscillator. Using the power supply sensitivity formula Sensitivity Percentage change in frequency = Percentage change in power supply voltage = Between 5V to 6V, the percentage change in power supply voltage = = 20% While the percentage change in frequency is = 3.575% VCO sensitivity to this supply voltage variation = = 17.875 % Between 4V to 5V, the percentage change in power supply voltage = = 25% While the percentage change in frequency is = 12.21% VCO sensitivity to this supply voltage variation = = 48.84% The inference from the above calculation shows that the sensitivity of this lock-in amplifier based micro-ohmmeter to power supply voltage increases with reducing supply voltage. The tuning range of the VCO refers to the range of oscillation frequencies Two important parameters in VCO design are linearity and sweep range. Linearity correlates the change in frequency or the VCO output to the change in the control voltage. The sweep range is the range of possible frequencies produced by VCO control voltage. The linearity Muting Detector Circuit The filtered output from the phase sensitive detector is a control voltage which, with Zero input ( short circuited probes) is about Vg volts . It goes more positive with increasing signal level. With maximum input(open circuited probes) the voltage will saturate near the positive supply rail. This would result in a loud high pitched tone from the oscillator, which is not what we want. We want the it to be mute when the probes are disconnected and to do this another operational amplifier is brought in to compare the control voltage with a reference voltage. Whenever the control voltage goes higher than the reference, the output will go negative. This allows a small current to be drawn through D1 and R25, which will keep the oscillator transistor switched off, stopping oscillation. The output voltage of an AM synchronous detector is compared with a reference potential level by a voltage comparator. A muting device connected with the output of the detector is controlled by a control circuit connected with the comparator. Through this control circuit, the detector output is immediately muted when the detector output level falls below the reference potential level, and the muting of the detector output is removed after a predetermined retardation when the detector output level exceeds the reference potential level. References 1 Bateson, S. January 2010, Electronic Signal Conditioning Labs, Teesside University, Middlesbrough 2 Hewes, J, (17.02.2010), 555 Timer, http://www.kpsec.freeuk.com/555timer.htm#astable 3 Instrumentation amplifier, (14.02.2010) http://en.wikipedia.org/wiki/Instrumentation_amplifier 4 Java, (19.01.2001), Voltage controlled oscillator, http://www.falstad.com/circuit/e-vco.html 13022010 5 Kuphaldt, T, (12.02.2010), Differentiator and Integrator Circuits, http://www.allaboutcircuits.com/vol_3/chpt_8/10.html 6 Low pass filter, (14.02.2010) http://en.wikipedia.org/wiki/Low-pass_filter 7 Quadrature Divider, (17.02.2010), http://www.patentstorm.us/patents/7425850/claims.html 8 Sallen-key low-pass filter (13.02.2010), http://www.ecircuitcentezr.com/Circuits/opsalkey1/opsalkey1.htm 9 Widerin, P, (13.02.2010), Quadrature Divider, http://www.freshpatents.com/Quadrature-divider-dt20070111ptan20070009077.php