Recursive randomsampling strategy for a digital wattmeter. While using three wattmeter method following difficulty is met with. It is often necessary to convert analog signal to an accurate digital number, and vice versa. Dynamometer type wattmeter working your electrical guide. We have strongly improved our sampling wattmeter for the measurement of low frequency power in the range of 45 hz to 55 hz. Pdf new digital multimeter for accurate measurement of. The response of the system agrees with that of a standard electrodynamic wattmeter within 0. Digital sampling method in the measurements of electrical. The sampled signals are digitized and the result is computed by numerical integration. Measurement of threephase power with the 2wattmeter. Pdf the paper presents the results of application of digital sampling method and a study of the errors caused in the.
Errors may creep in when measuring active power under nonsinusoidal and offnominal frequency conditions by a conventional regularly spaced sampling digital wattmeter rssdw due to the existence of higher order voltage and current harmonics, and asynchrony between the signal fundamental frequency and the sampling rate. A manual for selecting sampling techniques in research. Part i discussed the digital storage oscil loscope dso. In general, mphase power can be measured by means of m 1 wattmeters. Power in an electric circuit is the product multiplication of voltage and current, so any meter designed to measure power must account for both of these variables electrodynamometer movement. For each sample, the voltage is multiplied by the current at the same instant. The matter presented here is prepared by the author for their respective teaching assignments by referring the text books and reference books. Purposeful sampling is a technique widely used in qualitative research for the identification and selection of informationrich cases for the most effective use of limited resources patton, 2002. In the paper, an instrument for simultaneous measurement of active, reactive and apparent power is presented. Nonprobability sampling or judgment sampling depends on subjective judgment.
An early application of precision synchronous wave form sampling was the development of a digital wattmeter that used 15 bit successive approxima. Pdf real, reactive and apparent power computing using. Surface water sampling methods and analysis finalversion. A wattmeter is used to measure the voltage in an electronic circuit. In simple random sampling each member of population is equally likely to be chosen as part of the sample. Two wattmeter method of power measurement two wattmeter method can be employed to measure the power in a 3 phase, three wire star or delta connected the balanced or unbalanced load.
The decisions surrounding the sample design and methodology should be discussed with all the parties involved to ensure their agreement to the process and avoid problems during clearance. Measurements up to 5 khz can be made with somewhat greater uncertainties. This device is available in a purely electronic form too which is known as digital wattmeter. Errors in digital measurement of voltage, active and reactive powersand anonline correction for frequency drift. As shown in the above figure, the wattmeter has two sets of coils.
From these data a computer subsequently calculates the power. The traditional form of wattmeter is called as dynamometer wattmeter. Measurement of three phase power wattmeter methods. All lti systems can be thought of as lters, so, at least for lti systems, to. Salant, p62 the nonprobability method of sampling is a process where probabilities cannot be assigned to the units objectively, and hence it becomes difficult to determine the reliability of the sample. Sampling wattmeter the core of this setup is formed by two sampling voltmeters that simultaneously sample the voltage and current signal. The signalconditioning circuitry of the earlier wattmeter, which converted input voltages into 12b digital signals, was built into plugin modules. Both approaches have their own advantages and drawbacks. Insights from an overview of the methods literature abstract the methods literature regarding sampling in qualitative research is characterized by important inconsistencies and ambiguities, which can be problematic for students and researchers seeking a clear and coherent understanding. Surface water sampling methods and analysis 2 department of water despite the care taken in the preparation of this publication, there may be acceptable alternatives to the methods given to sample for various water quality variables. An improvement for dual channel sampling wattmeter international.
Figure 1 opposite contains a sample size lookup table for samples selected using simple random sampling, the most frequently used method in the office. Electrodynamic wattmeters are a design that goes back to the early 20th century. Convenience sampling is a type of nonprobability sampling in which people are sampled simply because they are convenient sources of data for researchers. The wattmeter is an instrument for measuring the electric power or the supply rate of electrical energy in watts of any given circuit. In digital ac voltmeters based on analog methods of ac voltage conversion, the dc. As the input value changes, the moving system or pointer exhibits a smooth. A manual for selecting sampling techniques in research 4 preface the manual for sampling techniques used in social sciences is an effort to describe various types of sampling methodologies that are used in researches of social sciences in an easy and understandable way. The rf sampler provides a low power sample of the signal being transmitted through the wattmeters linesection. In the case of 3 phase, 3 wire star connected load, it is difficult to get a neutral point which is required for connection.
But in these instruments, the operating field is produced by the fixed coil instead of a permanent magnet. Different algorithms are developed and reported in the literature for using digital samples of the voltage and current in the design of digital wattmeters 1. Design and implementation of a high accuracy sampling. In probability sampling, each element in the population has a known nonzero chance of being selected through the use of a. The measurement methods can be analog or digital methods, deflection or null methods, active or passive methods, direct or indirect methods and absolute or secondary methods. Yokogawa europe sampling wattmeter for low frequencies.
Simultaneously, watt readings using a standard commercially available analogue wattmeter were also taken. Pdf recursive random sampling strategy for a digital. Pdf implementation of a digital wattmeter on fpga researchgate. It is strongly recommended that this publication be. In special cases, when this method is necessary to use, an artificial star can be formed. The presence of nonsinusoidal regimes makes the use of the shannon theorem more difficult. Its functionality is based on a pwm intermediary conversion multichannel analog to digital converter adc. Average electric power can be measured by a system that samples voltages and currents at. Nonprobability samples are most often used in qualitative research, although quantitative studies may sometimes need to use a. Digital method for power frequency measurement using.
The precision measurement of alternating ac sig nals by digital sampling can be best accomplished with the use of a pll and proper method was suggested in. Fir digital filter design by using frequency sampling method 46 university bulletin issue no. Design and hardware implementation of a digital wattmeter. A special meter movement designed especially for power measurement is called the dynamometer movement, and is similar to a darsonval or weston movement in that a lightweight coil of wire is.
The three main types are electrodynamic, electronic and digital. A wattmeter does a complex job, measuring the power flowing through an electrical circuit. The dynamometer wattmeter works on the motor principle. Pdf digital sampling method in the measurements of electrical. Digital wattmeter using a sampling method ieee journals. This is known as the twowattmeter method of measuring threephase power.
In this strategy each sampling instant is obtained by adding a prefixed constant lag plus. Digital wattmeter using a sampling method abstract. Pdf digital sampling method in the measurements of. A modern digital wattmeter samples the voltage and current thousands of times a second. By using a more stable generator and by correcting for the dc offset in. The instrument is implemented on an alteras flex10k70 field programmable gate array fpga device for single phase. In two wattmeter method the current coils of the wattmeter are connected with any two lines, say r and y and the potential coil of each wattmeter is joined on the same line, the third line i.
Digital multirate algorithms for measurement of voltage, current,power and. Hi friends, in this article, i am discussing the dynamometer type wattmeter working principle and related information, if you are interested in it then you at the right place these are basically moving coil instruments. Simple random sampling also referred to as random sampling is the purest and the most straightforward probability sampling strategy. Turgel, digital wattmeter using a sampling method, ieee. The dswm is a digital multi functional sampling watt meter with a basic. A modern digital sampling wattmeter, such as any of the tektronix power analyzers, multiplies instantaneous samples of voltage and current together to calculate instantaneous watts and then takes an average of the instantaneous watts over one cycle to display the true power. Sampling techniques in this lecture, our focus only on sampling to really understand and mastery various. A calibration via a direct reading method using a 9100 wavetek calibrator at nis is compared to the calibration through an indirect method by comparing it to an 8 12 hp3458a digital multimeter. Originally only a tool of professionals there are now many different types of the device available that are both cheap and easy to use and available for home use. Since the earlier instrument was modular, the development of the new wattmeter was simplified by utilizing elements from the previous wattmeter in the design. A recursive random sampling strategy is proposed for the implementation of a digital broadband wattmeter.
This paper presents design and implementation of a modified. A practical guide to sampling national audit office. Sampling techniques for electric power measurement govinfo. An overview of the setup is schematically depicted in figure 1. Similar design is also available for ade7751 and, further details. It is also the most popular method for choosing a sample among population for a wide range of purposes. Measure the temperature of the sample and adjust the temperature controller of the ph meter to that of the sample temperature. Pdf improved sampling wattmeter for low frequencies 45. In special cases, when this method is necessary to use. This involves identifying and selecting individuals or groups of individuals that are especially knowledgeable about or experienced with a phenomenon of interest. Construction of digital toanalogue converters using different techniques, namely the scaled resistors into summing junction, and the r2r ladder. Now we nally have the analytical tools to begin to design discretetime systems. Another example is in the hewlett packard 3458a, in which multimeter three methods of conversion are used.
We have used several lamps having watt ratings of 40, 60 and 100watt as loads and measured real power dissipated at those loads using our designed digital wattmeter. It fits roughly 60% of logic cells without any resource. In fact, the bandwidth of a strategy using asynchronous equally spaced samples is certainly smaller than the sampling fre quency l, 2. Wattmeter design dc metering circuits electronics textbook.
Average electric power can be measured by a system that samples voltages and currents at predetermined intervals. The real power divided by the apparent voltamperes va is the power factor. It simultaneously measures the voltage and current values and multiplies them to give power in watts. Bird model 43 wattmeter bird 4431 thruline wattmeter the bird 4431 rf sampling wattmeter is the same as the bird 43 thruline wattmeter except for an rf signal sampler probe. Standards for waveform metrology based on digital techniques. Purposeful sampling for qualitative data collection and. The models of digital sampling operations and matlab applications show which the sampling frequency for a minimum of errors is. The method is valid for both balanced and unbalanced circuits with either the load or the source unbalanced. Several types of digital wattmeter based on sampling method have been presented in different literature.
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