1.
Vlinderklep
–
A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk, operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other designs as well as being lighter in weight. The disc is positioned in the center of the pipe, passing through the disc is a rod connected to an actuator on the outside of the valve, rotating the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is present within the flow, so a pressure drop is always induced in the flow. A butterfly valve is from a family of valves called quarter-turn valves, in operation, the valve is fully open or closed when the disc is rotated a quarter turn. The butterfly is a disc mounted on a rod. When the valve is closed, the disc is turned so that it completely blocks off the passageway, when the valve is fully open, the disc is rotated a quarter turn so that it allows an almost unrestricted passage of the fluid. The valve may also be opened incrementally to throttle flow, there are different kinds of butterfly valves, each adapted for different pressures and different usage. The zero-offset butterfly valve, which uses the flexibility of rubber, has the lowest pressure rating. The high-performance double offset butterfly valve, used in slightly higher-pressure systems, is offset from the line of the disc seat and body seal. This creates a cam action during operation to lift the seat out of the resulting in less friction than is created in the zero offset design. The valve best suited for high-pressure systems is the triple offset butterfly valve, in this valve the disc seat contact axis is offset, which acts to virtually eliminate sliding contact between disc and seat. In the case of triple offset valves the seat is made of metal so that it can be machined such as to achieve a bubble tight shut-off when in contact with the disc, concentric butterfly valves – this type of valve has a resilient rubber seat with a metal disc. Doubly-eccentric butterfly valves – different type of materials is used for seat, triply-eccentric butterfly valves – the seats are either laminated or solid metal seat design. The wafer style butterfly valve is designed to maintain a seal against bi-directional pressure differential to prevent any backflow in systems designed for unidirectional flow. It accomplishes this with a tightly fitting seal, i. e. gasket, o-ring, precision machined, lug-style valves have threaded inserts at both sides of the valve body. This allows them to be installed into a system using two sets of bolts and no nuts, the valve is installed between two flanges using a separate set of bolts for each flange
2.
Sensor
–
A sensor is always used with other electronics, whether as simple as a light or as complex as a computer. Moreover, analog sensors such as potentiometers and force-sensing resistors are still widely used, applications include manufacturing and machinery, airplanes and aerospace, cars, medicine, robotics and many other aspects of our day-to-day life. A sensors sensitivity indicates how much the output changes when the input quantity being measured changes. For instance, if the mercury in a thermometer moves 1 cm when the changes by 1 °C. Some sensors can also affect what they measure, for instance, Sensors are usually designed to have a small effect on what is measured, making the sensor smaller often improves this and may introduce other advantages. Technological progress allows more and more sensors to be manufactured on a scale as microsensors using MEMS technology. In most cases, a microsensor reaches a higher speed. Most sensors have a transfer function. The sensitivity is defined as the ratio between the output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is the slope of the transfer function. Converting the sensors electrical output to the measured units requires dividing the output by the slope. In addition, an offset is added or subtracted. For example -40 must be added to the output if 0 V output corresponds to -40 C input, for an analog sensor signal to be processed, or used in digital equipment, it needs to be converted to a digital signal, using an analog-to-digital converter. The full scale range defines the maximum and minimum values of the measured property, the sensitivity may in practice differ from the value specified. This is called a sensitivity error and this is an error in the slope of a linear transfer function. If the output differs from the correct value by a constant. This is an error in the y-intercept of a transfer function. Nonlinearity is deviation of a transfer function from a straight line transfer function
3.
Microprocessor
–
A microprocessor is a computer processor which incorporates the functions of a computers central processing unit on a single integrated circuit, or at most a few integrated circuits. Microprocessors contain both combinational logic and sequential digital logic, Microprocessors operate on numbers and symbols represented in the binary numeral system. The integration of a whole CPU onto a chip or on a few chips greatly reduced the cost of processing power. Integrated circuit processors are produced in numbers by highly automated processes resulting in a low per unit cost. Single-chip processors increase reliability as there are many electrical connections to fail. As microprocessor designs get better, the cost of manufacturing a chip generally stays the same, before microprocessors, small computers had been built using racks of circuit boards with many medium- and small-scale integrated circuits. Microprocessors combined this into one or a few large-scale ICs, the internal arrangement of a microprocessor varies depending on the age of the design and the intended purposes of the microprocessor. Advancing technology makes more complex and powerful chips feasible to manufacture, a minimal hypothetical microprocessor might only include an arithmetic logic unit and a control logic section. The ALU performs operations such as addition, subtraction, and operations such as AND or OR, each operation of the ALU sets one or more flags in a status register, which indicate the results of the last operation. The control logic retrieves instruction codes from memory and initiates the sequence of operations required for the ALU to carry out the instruction, a single operation code might affect many individual data paths, registers, and other elements of the processor. As integrated circuit technology advanced, it was feasible to manufacture more and more complex processors on a single chip, the size of data objects became larger, allowing more transistors on a chip allowed word sizes to increase from 4- and 8-bit words up to todays 64-bit words. Additional features were added to the architecture, more on-chip registers sped up programs. Floating-point arithmetic, for example, was not available on 8-bit microprocessors. Integration of the point unit first as a separate integrated circuit and then as part of the same microprocessor chip. Occasionally, physical limitations of integrated circuits made such practices as a bit slice approach necessary, instead of processing all of a long word on one integrated circuit, multiple circuits in parallel processed subsets of each data word. With the ability to put large numbers of transistors on one chip and this CPU cache has the advantage of faster access than off-chip memory, and increases the processing speed of the system for many applications. Processor clock frequency has increased more rapidly than external memory speed, except in the recent past, a microprocessor is a general purpose system. Several specialized processing devices have followed from the technology, A digital signal processor is specialized for signal processing, graphics processing units are processors designed primarily for realtime rendering of 3D images
4.
Digitale signaalprocessor
–
A digital signal processor is a specialized microprocessor, with its architecture optimized for the operational needs of digital signal processing. The goal of DSPs is usually to measure, filter or compress continuous real-world analog signals, DSPs often use special memory architectures that are able to fetch multiple data or instructions at the same time. Digital signal processing algorithms typically require a number of mathematical operations to be performed quickly and repeatedly on a series of data samples. Signals are constantly converted from analog to digital, manipulated digitally, many DSP applications have constraints on latency, that is, for the system to work, the DSP operation must be completed within some fixed time, and deferred processing is not viable. A specialized digital signal processor, however, will tend to provide a lower-cost solution, with performance, lower latency. For example, the SES-12 and SES-14 satellites from operator SES, the architecture of a digital signal processor is optimized specifically for digital signal processing. Most also support some of the features as a processor or microcontroller. Some useful features for optimizing DSP algorithms are outlined below, sometimes various sticky bits operation modes are available. DSPs can sometimes rely on supporting code to know about cache hierarchies and this is a tradeoff that allows for better performance. In addition, extensive use of DMA is employed, DSPs frequently use multi-tasking operating systems, but have no support for virtual memory or memory protection. Operating systems that use virtual memory require more time for context switching among processes, the AMD2901 bit-slice chip with its family of components was a very popular choice. There were reference designs from AMD, but very often the specifics of a design were application specific. These bit slice architectures would sometimes include a peripheral multiplier chip, examples of these multipliers were a series from TRW including the TDC1008 and TDC1010, some of which included an accumulator, providing the requisite multiply–accumulate function. In 1976, Richard Wiggins proposed the Speak & Spell concept to Paul Breedlove, Larry Brantingham, two years later in 1978 they produced the first Speak & Spell, with the technological centerpiece being the TMS5100, the industrys first digital signal processor. It also set other milestones, being the first chip to use Linear predictive coding to perform speech synthesis, in 1978, Intel released the 2920 as an analog signal processor. It had an on-chip ADC/DAC with a signal processor. In 1979, AMI released the S2811 and it was designed as a microprocessor peripheral, and it had to be initialized by the host. The S2811 was likewise not successful in the market, in 1980 the first stand-alone, complete DSPs – the NEC µPD7720 and AT&T DSP1 – were presented at the International Solid-State Circuits Conference 80
5.
Thermistor
–
A thermistor is a type of resistor whose resistance is dependent on temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor, thermistors are widely used as inrush current limiter, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements. Thermistors are of two fundamental types, With NTC, resistance decreases as temperature rises to protect against inrush overvoltage conditions. Commonly installed in parallel as a current sink, with PTC, resistance increases as temperature rises to protect against overcurrent conditions. Commonly installed in series as a resettable fuse, thermistors differ from resistance temperature detectors in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. If k is positive, the resistance increases with increasing temperature, if k is negative, the resistance decreases with increasing temperature, and the device is called a negative temperature coefficient thermistor. Resistors that are not thermistors are designed to have a k as close to 0 as possible, instead of the temperature coefficient k, sometimes the temperature coefficient of resistance α T is used. It is defined as α T =1 R d R d T and this α T coefficient should not be confused with the a parameter below. In practice, the linear approximation works only over a temperature range. For accurate temperature measurements, the curve of the device must be described in more detail. The Steinhart–Hart equation is a widely used third-order approximation,1 T = a + b ln + c 3 where a, b and c are called the Steinhart–Hart parameters, T is the absolute temperature and R is the resistance. As an example, typical values for a thermistor with a resistance of 3 kΩ at room temperature are, a =1.40 ×10 −3 b =2.37 ×10 −4 c =9. Solving for R yields, R = R0 e − B or, alternatively and this can be solved for the temperature, T = B ln The B-parameter equation can also be written as ln R = B / T + ln r ∞. This can be used to convert the function of resistance vs. temperature of a thermistor into a function of ln R vs.1 / T. The average slope of this function will yield an estimate of the value of the B parameter. Many NTC thermistors are made from a disc, rod, plate. They work because raising the temperature of a semiconductor increases the number of charge carriers - it promotes them into the conduction band. The more charge carriers that are available, the current a material can conduct
6.
Brug van Wheatstone
–
A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of a bridge is its ability to provide extremely accurate measurements. Its operation is similar to the original potentiometer, the Wheatstone bridge was invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. One of the Wheatstone bridges initial uses was for the purpose of soils analysis, in the figure, R x is the unknown resistance to be measured, R1, R2, and R3 are resistors of known resistance and the resistance of R2 is adjustable. If the bridge is unbalanced, the direction of the current indicates whether R2 is too high or too low, R2 is varied until there is no current through the galvanometer, which then reads zero. Detecting zero current with a galvanometer can be done to extremely high accuracy, therefore, if R1, R2, and R3 are known to high precision, then R x can be measured to high precision. Very small changes in R x disrupt the balance and are readily detected and this setup is frequently used in strain gauge and resistance thermometer measurements, as it is usually faster to read a voltage level off a meter than to adjust a resistance to zero the voltage. The equation for this is, V G = V s where VG is the voltage of node D relative to node B, the Wheatstone bridge illustrates the concept of a difference measurement, which can be extremely accurate. Variations on the Wheatstone bridge can be used to measure capacitance, inductance, impedance and other quantities, such as the amount of gases in a sample. The Kelvin bridge was adapted from the Wheatstone bridge for measuring very low resistances. The concept was extended to alternating current measurements by James Clerk Maxwell in 1865, the Wheatstone bridge is the fundamental bridge, but there are other modifications that can be made to measure various kinds of resistances when the fundamental Wheatstone bridge is not suitable. Some of the modifications are, Carey Foster bridge, for measuring small resistances Kelvin bridge, for measuring small four-terminal resistances Maxwell bridge, Wheatstone Bridge – Interactive Tutorial National High Magnetic Field Laboratory Test Set I-49
7.
Analoog-digitaalomzetter
–
In electronics, an analog-to-digital converter is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. Typically the digital output is a twos complement binary number that is proportional to the input, due to the complexity and the need for precisely matched components, all but the most specialized ADCs are implemented as integrated circuits. A digital-to-analog converter performs the function, it converts a digital signal into an analog signal. The conversion involves quantization of the input, so it necessarily introduces a small amount of error, furthermore, instead of continuously performing the conversion, an ADC does the conversion periodically, sampling the input. The result is a sequence of values that have been converted from a continuous-time and continuous-amplitude analog signal to a discrete-time. An ADC is defined by its bandwidth and its signal-to-noise ratio, the bandwidth of an ADC is characterized primarily by its sampling rate. The dynamic range of an ADC is influenced by many factors, including the resolution, linearity and accuracy, aliasing and jitter. The dynamic range of an ADC is often summarized in terms of its number of bits. An ideal ADC has an ENOB equal to its resolution, ADCs are chosen to match the bandwidth and required signal-to-noise ratio of the signal to be quantized. If an ADC operates at a rate greater than twice the bandwidth of the signal, then perfect reconstruction is possible given an ideal ADC. The presence of quantization error limits the range of even an ideal ADC. However, if the range of the ADC exceeds that of the input signal. The resolution of the converter indicates the number of values it can produce over the range of analog values. The resolution determines the magnitude of the error and therefore determines the maximum possible average signal to noise ratio for an ideal ADC without the use of oversampling. The values are stored electronically in binary form, so the resolution is usually expressed in bits. In consequence, the number of discrete values available, or levels, is assumed to be a power of two, for example, an ADC with a resolution of 8 bits can encode an analog input to one in 256 different levels, since 28 =256. The values can represent the ranges from 0 to 255 or from −128 to 127, resolution can also be defined electrically, and expressed in volts. The minimum change in required to guarantee a change in the output code level is called the least significant bit voltage
8.
4-20 mA
–
In electrical signalling an analog current loop is used where a device must be monitored or controlled remotely over a pair of conductors. Only one current level can be present at any time and they are also used to transmit controller outputs to the modulating field devices such as control valves. These loops have the advantages of simplicity and noise immunity, and have an international user. Various Automation Protocols may replace analog current loops, but 4-20 mA is still an industrial standard. In industrial process control, analog 4–20 mA current loops are used for electronic signalling. These loops are used both for carrying information from field instrumentation, and carrying control signals to the process modulating devices. The key advantages of the current loop are, The loop can often power the device, with power supplied by the controller. Many instrumentation manufacturers produce 4-20 mA sensors which are loop powered, the live or elevated zero of 4 mA allows powering of the device even with no process signal output from the field transmitter. The accuracy of the signal is not affected by voltage drop in the interconnecting wiring and it has high noise immunity as it is low impedance circuit usually through twisted pair conductors. It is self-monitoring, currents less than 3.8 mA or more than 20.5 mA are taken to indicate a fault and it can be carried over long cables up to the limit of the resistance for the voltage used. In line displays can be inserted and powered by the loop, easy conversion to voltage using a resistor. Loop powered I to P converters can convert the 4-20 mA signal to a 3-15 psi pneumatic output for control valves, field instrumentation measurements are such as pressure, temperature, level, flow, pH or other process variables. A current loop can also be used to control a valve positioner or other output actuator, since input terminals of instruments may have one side of the current loop input tied to the chassis ground, analog isolators may be required when connecting several instruments in series. The relationship between current value and process variable measurement is set by calibration, which assigns different ranges of engineering units to the span between 4 and 20 mA. The mapping between engineering units and current can be inverted, so that 4 mA represents the maximum and 20 mA the minimum, depending on the source of current for the loop, devices may be classified as active or passive. For example, a chart recorder may provide power to a pressure transmitter. The pressure transmitter modulates the current on the loop to send the signal to the strip chart recorder, another loop may contain two passive chart recorders, a passive pressure transmitter, and a 24 V battery. Note that a 4-wire instrument has a power supply separate from the current loop
9.
Volt (eenheid)
–
The volt is the derived unit for electric potential, electric potential difference, and electromotive force. One volt is defined as the difference in potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. It is also equal to the difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can also be expressed as amperes times ohms, watts per ampere, or joules per coulomb, for the Josephson constant, KJ = 2e/h, the conventional value KJ-90 is used, K J-90 =0.4835979 GHz μ V. This standard is typically realized using an array of several thousand or tens of thousands of junctions. Empirically, several experiments have shown that the method is independent of device design, material, measurement setup, etc. in the water-flow analogy sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage is likened to difference in water pressure. Current is proportional to the diameter of the pipe or the amount of water flowing at that pressure. A resistor would be a reduced diameter somewhere in the piping, the relationship between voltage and current is defined by Ohms Law. Ohms Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems, the voltage produced by each electrochemical cell in a battery is determined by the chemistry of that cell. Cells can be combined in series for multiples of that voltage, mechanical generators can usually be constructed to any voltage in a range of feasibility. High-voltage electric power lines,110 kV and up Lightning, Varies greatly. Volta had determined that the most effective pair of metals to produce electricity was zinc. In 1861, Latimer Clark and Sir Charles Bright coined the name volt for the unit of resistance, by 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad. In 1881, the International Electrical Congress, now the International Electrotechnical Commission and they made the volt equal to 108 cgs units of voltage, the cgs system at the time being the customary system of units in science. At that time, the volt was defined as the difference across a conductor when a current of one ampere dissipates one watt of power. The international volt was defined in 1893 as 1/1.434 of the emf of a Clark cell and this definition was abandoned in 1908 in favor of a definition based on the international ohm and international ampere until the entire set of reproducible units was abandoned in 1948. Prior to the development of the Josephson junction voltage standard, the volt was maintained in laboratories using specially constructed batteries called standard cells
10.
Proportionele regelaar
–
A proportional control system is a type of linear feedback control system. Two classic mechanical examples are the toilet bowl float proportioning valve, on-off control will work where the overall system has a relatively long response time, but can result in instability if the system being controlled has a rapid response time. Proportional control overcomes this by modulating the output to the controlling device, an analogy to on-off control is driving a car by applying either full power or no power and varying the duty cycle, to control speed. The power would be on until the speed is reached. When the speed falls below the target, with a certain hysteresis and it can be seen that this looks like pulse-width modulation, but would obviously result in poor control and large variations in speed. The more powerful the engine, the greater the instability, the heavier the car, stability may be expressed as correlating to the power-to-weight ratio of the vehicle. Proportional control is how most drivers control the speed of a car, further refinements like PID control would help compensate for additional variables like hills, where the amount of power needed for a given speed change would vary. This would be accounted for by the function of the PID control. In the proportional control algorithm, the output is proportional to the error signal. In other words, the output of a controller is the multiplication product of the error signal. This can be expressed as, P o u t = K p e + p 0 where p 0. P o u t, Output of the proportional controller K p, Proportional gain e, E = S P − P V SP, Set point PV, Process variable Constraints, P o u t cannot be greater than 1 or 100%. P o u t can be less than 0 when the controller is in cooling mode rather than heating mode, in any case P o u t cannot be less than -1 or -100%. On a real plant valves cannot open more than 100% however mathematical models may summon from nowhere, qualifications, It is preferable to express K p as a pure number. To do this e should be written as a ratio with the span of the instrument and this span is in the same units as error so the ratio is pure number. Proportional Control Action leaves out an error called Offset Error and this error is called an Offset Error. Proportional Band is the band of Controller Output over which the Final Control Element will move from one extreme to another. This is the case with ON-OFF Controllers, where K p is very high and hence, for even a small error, PI controller - special case of PID controller Proportional control compared to ON-OFF or bang-bang control d vvg
