Resistor Manufacture and Optimization - Book Report/Review Example

Resistor Manufacture and Optimization Part I: Current Resistor Types and Manufacturing Techniques Resistors are the most commonly used electric circuit component. The resistor is a passive component, which is burdened with regulating voltages and currents, depending on their connectivity in circuit. Although common, the resistor can be manufactured in numerous ways. Each technique provides the resistor with its own set of characteristics to fit certain applications. The operating principle behind a resistor is that the component is comprised of a conducting material that has a specific value of resistivity. The conducting material is connected to the circuit via electrodes and these components are insulated. The technique of construction affects the characteristics of the resistor when it is used in high frequency fields. The resistor develops inductor and capacitor like traits in high frequency fields, referred to as parasitic inductance and capacitance. Carbon composition resistors Carbon composition (carbon comp) resistors are one of the most common resistor manufacture technique. The composition essence in the resistor is as a result of the use of carbon as a mixing component. The conductive material in the resistor is comprised of carbon and stabilizing elements. Mixing is done by the use of ceramic clay as a stabilizing element and carbon or graphite ground in fine form. The amount of carbon in the mixture directly affects the resistance put up by the component, where this is determined by the ratio of graphite of carbon to ceramic clay. This type of resistor is cylindrical in shape, as the carbon is housed inside, and is coated (insulated) with resin or phenolic to reduce parasitic inductance. The resistors provide resistivity ranging from 0.25 to 2 watts and handles overloads better. Since the heat generated in resistivity is distributed throughout the resistor, the heat dissipated by the resistor is thus evenly distributed in the component, unlike other types of capacitors. This resistor is thus a great choice for pulsating and transient circuits where the current flow displays overshooting traits. Unfortunately, this type of resistor is affected by operational conditions of the surrounding such as the ambient temperature and humidity. As a result, this type of resistors is unreliable for use in precision and stable circuits. These traits thus affect the noise output of the resistor in the circuits. Noise and stability of the carbon comp resistors is increased with increase in the operating temperatures. This makes these resistors best for applications of low to medium power. In practice, the carbon comp resistors are denoted by a ‘CR’ prefix and come in three tolerance ranges E 6 (± 20%), E 12 (± 10%), and E 24 (± 5%). These are high tolerances that make them less sensitive to small precision currents. The resistors are cheap and are widely used in common circuit components. Film resistors Film resistors are the second type of resistors common in the market. In this case, the conductive material consists of metal, carbon and metal oxide films. The conductive material is laid down in the insulating substrate made up of glass or ceramic clay. The resistivity of this type of resistor is determined by the thickness of the conduction strip, which classifies the resistors into either thin or thick (thick film resistors and thin film resistors), the degree of thickness thus controls the degree of resistivity. The materials that are commonly used in the manufacture of these resistors include pure metal films of metals such as nickel and oxides such as tin-oxide. Due to the conductive material being quick to react, their resistivity is offered in extremely accurate values. In the production process, laser engraved spirals are characteristic to this type of resistor. The spirals cut over the conductive material increase the conductance of the resistor, a process referred to as trimming. The resistors being extremely accurate have tolerances of 1% (or less). In addition to the resistors having low tolerances, they also have extremely high resistivity values, such as 10 million Ohms. The resistors of this type are used in circuits that are more precise compared to the carbon comp resistors. However, these resistors cannot be used in high-powered and in fluctuating circuits, for a power overload shall change the resistor value completely. In addition, the instantaneous overloads create a hotspot since as opposed to the carbon resistors, heat distribution and dissipation is not even. The common use of this type of resistors falls within the surface mount components, and in the case of the thin film, the recommended operating power falls within the 0.1 to 0.25 watts. The resistors are hardly affected by the surrounding conditions of temperature and humidity and have a low noise production index. Wire wound resistors Just as the name suggests, the resistors are made by wounding a thin metal allot, commonly Nichrome, onto a former, ceramic and connected to electrodes at both ends. The thin alloy wire is wound just as the helix in the thin film resistors, but in this case, by a machine that sets the wire depending on the number of wounds required to attain a certain resistivity value. The result of the technique is high accuracy and precision resistors, occupying more volume than preceding types. These resistors have the capability of providing precision values of 0.01 Ω (Ohms) to 100 KΩ, based on the wire gauge, windings and its resistivity value. Their accuracy and precision values make this type of resistors preferable for the measuring circuits, but have an advantage of being able to handle higher currents compared to equivalent resistor types. The resistor is capable of handling power in the range of one watt to 300 watts. These resistors generate heat as they operate and are usually fitted with an aluminum case that has grooves to help in heat dissipation, since the design of the resistors normally considers air as a cooling agent, tough other technologies are being used for that purpose. When it comes to parasitic influence, the wounding on the ceramic formers bring about the fact that the resistor acts as a solenoid and produces inductance as it operates. The interference by the resistor thus means that the wound resistors cannot be used in fields where inductance and magnetism are contributors to the output, which include RF and audio circuits. This inductive influence can result into noise in the audio circuits. The environmental factors hardly affect the performance of these resistors, unless they are on the extremes. Ceramic and metal oxide resistors Ceramic and metal oxide resistors are a class of high-power and non-inductive resistors, where the components i.e. Cermet (ceramic-metal mix) or metal oxide resistors act as the conductive components. They are designed and constructed just as the carbon-comp resistors, but substitutes the cermet or metal oxide for the carbon-and clay composition material. Part II: Analyses of Resistor Manufacturing Output Mean of production: which is taken as the number of produced resistors, dived by the resitivity values of the resistors generated. Thus for a bunch of a single machine the mean is given by: 10,000/23= 434.78 (approximately 435 pieces) For both machines then the mean is (10,000)2/23= 869.565 (approximately 870 pieces) The mode of production for machine 1 is the resistor of 102 Ohms whereas the mean of machine 2 is the 100 Ohm resistor. For both machines the mode of production is the 101 Ohm resistor with 2192 units being produced by the two machines. Using the cummulative frequency, the 101 Ohm resistor is the median of production. From the data provided, machine 1 needs recalibration to impove its production efficiency. The yeild of machine 1 within the required resistor is lower than that of machine 2. In additrion, the machine has a higher rejection production capacity. The data tells me that the production process is bound to have some rejectiuon and less than adequate produce. The information emphasizes why a grading system is used and why the pricing differs within the grades. The pricing to the thousandth of the pound informs me of the treqyuired production capcity. The production process has to meet the critical mass for it to be sustainable and thus use of the thousands eleviates the problem of accountability per single unit produced. Torelance Description Unit sales value Resistor values Machine 1 Machine 2 Frequency 1% Premium 0.016 100, 101,99 2855 3334 6,189 2% High 0.012 102, 98 1735 1938 3,673 5% Standard 0.005 103,104,105,95,96,97 3681 3586 7,267 10% Low 0.001 106 – 110, 90-94 1656 1118 2,774 >10% Reject 0 Read More