Electrical field, e, is the negative of the gradient in electrical potential, i. The conductivity meter then uses the conductance and cell constant to display the conductivity. Congress in 1821, john quincy adams said, weights and measures may be. Use whenever possible 2 method of high gain feedback. A current meter is oceanographic device for flow measurement by mechanical, tilt, acoustical or electrical means.
Electrical energy meters principles and applications. The initial results showed an overall mean difference between the two methods that was very low. Water flow meter calibration with a master meter method. Comparison of discharge measurement by current meter and. There are a wide variety of sensors, and each sensor is suitable for a specific current range and environmental condition. Choose the right currentmeasurement technique for your. The device according to claim 1 wherein said output signal driver electrically connects to the cable linking the cmsp and the current meter, and includes means to relay a signal through said cable to permit an operator to count and monitor the revolutions of the current meter. Both the current and the potential are used to calculate the conductance iv. The threewattmeter method can also be used in the absence of a neutral conductor if an artificial neutral is available. The manual concentrates on the current meter streamflow measurement by wading. In the simplest method, a current meter turns with the flow of the river or stream. If this meter is to have full deflection at 5a, what is the value of the shunt resistance to be used.
The first step in that process is to decide whether to use indirect or direct. Use ofcurrent meters for continuous measurement offlows. Types of currentmeter measurements currentmeter discharge measurements are classified according to the type of equipment used and the nature of the station. Students should download above file and unzip in on hisher computer. The most common method used by the usgs for measuring velocity is with a current meter. Electrical measurements pdf notes em pdf notes smartzworld. Potential and current transformers, ratio and phase angle errors, phasor diagram, methods of minimizing errors. The task of the meter designer is to take a given meter movement and design the necessary external circuitry for fullscale indication at some specified amount of voltage or current. The establishment of measurement standards thus became the prerogative of the king or empe ror, and this right has since been assumed by all governments. Master meter method is an efficient way to calibrate flow meters with less time and costs. History is replete with examples that sh ow the importance of measurements and standa rds.
Vibrating reed type, electrical resonance type moduleii 10 hours instrument transformers. The meter measures only the voltage and current reaching the meter terminals. However, the guidelines of master meter method have not been established completely. Direct reading type eddy current instruments indicate conductivity in percent iacs %iacs and indirect type eddy current instruments are normally scaled in microamperes. A fairly new method called the acoustic scintillation flow measurement asfm has been used and compared to the cm method. The conductivity meter a typical conductivity meter applies an alternating current i at an optimal frequency1 to two active electrodes and measures the potential v.
A mid20thcentury realization is the ekman current meter which drops balls into a container to count the number of rotations. More often, the generated current is rectified and measured by a moving coil meter. Download and process s4 current meter data youtube. We have 3 thermo scientific orion star a215 manuals available for free pdf download.
This paper presents a rapid method for propeller current meter calibration, enabling calibration of current meters in. Current meters and open channel meters have been a speciality of valeports since the company was first formed in 1969. Realtime reporting of electricity measurement improves consumer awareness leading to waste reduction thus lower. Current sensing resistor description a current sensor is a device that detects and converts current to an easily measured output voltage, which is proportional to the current through the measured path.
The electrical measurements notes pdf em notes pdf book starts with the topics covering control and damping torques, design considerations type of p. A measuring system with three multipliers is required for 4wire threephase systems of unbalanced load with neutral conductor n. The cup wheel rotates due to relative velocity between water and the cup wheel. The constantvoltage method is used to measure the resistivity. Simplified processing method for meter data analysis. Types of current meter measurements current meter discharge measurements are classified according to the type of equipment used and the nature of the station. The roberts radio current meter is a device mounted on a moored buoy and transmits its findings via radio to a servicing vessel.
Typical current meter method divide stream cross section into transects 815 total measure velocity in each with meter at 60% depth in shallow water for a constant angular frequency to, the current is proportional to the applied voltage v. It is an instrument for measuring the velocity of flow of a fluid as water in a stream. The resistor is a direct method of current measurement that has the benefit of simplicity and linearity. The following typical percentage component uncertainty values are taken from iso 748. The primary current in the current coil is obtained from the current output phase l1 of the c300 with expanded uncertainty 0. Components and methods for current measurement vishay. The speed of rotation of the cup wheel is a function of the velocity of flow. The uncertainty in a current meter measurement sciencedirect. The fullscale deflection current of an ammeter is 1 ma and its internal. Instrument transformer theory and testing steve hudson, pe. The current sense resi stor is placed in line with the current being measured and the resultant current flow causes a small amount of power to be converted. For this document, the phrase data processing is the method used to adjust, clean up, or fix suspect building. Us6618680b2 signal processor apparatus for rotating. Meters, double element and three element dynamometer.
Here you can download the free lecture notes of electrical measurements pdf notes em pdf notes materials with multiple file links. The master meter method has simpler flow configuration than the gravimetric flow measurement method requires. Us6618680b2 signal processor apparatus for rotating water. They come in many shapes and sizes for different applications. The fullscale deflection current of an ammeter is 1 ma and its internal resistance is 100ohm. Mar 07, 2017 in this method, a special propeller type current meter which is free to move about a vertical axis is towed in a boat at a velocity vb at right angle to the stream flow. Many studies of current meter performance have been conducted by researchers thibodeaux, 1992.
Vc mto rms f 73 for a constant angular frequency to, the current is proportional to the applied voltage v. Many studies of currentmeter performance have been conducted by researchers thibodeaux, 1992. Currentmeter is rated in a long tank say 150 m long with sectional area 4 m x 2. The zip file contains labview vis and other files which will be used in some of the experiments during the course.
The ott mf pro saves time in the field by automatically calculating discharge and its electromagnetic sensor head is maintenancefree, ideal for use in lowflow environments, and unaffected by large amounts of organic matter. That is, the meter will automatically select the most appropriate range for making the measurement. Meter, sensor, or communication errors because of broken equipment meter, sensor, or communication software malfunctions meter, sensor, or communication system replacement or resetrestart. Current meter a current meter is oceanographic device for flow measurement by mechanical, tilt, acoustical or electrical means. Exposure time of current meter at each of 2 points. The method is valid for both balanced and unbalanced circuits with either the load or the source unbalanced. Electrical measurements lab manual pdf em lab manual pdf. The present invention comprises a hand held, battery operated water current velocity measuring device designed for use with contact closure water current meters. Yarnell and naglers 1931 study on mechanical current meters is one often referenced. Download fulltext pdf proving by master meter method article pdf available in measurement and control london institute of measurement and control 355. The matter presented here is prepared by the author for their respective teaching assignments by referring the text books and reference books. Low level measurements handbook 7th edition tektronix. Introduction to measurement methods discharge computations by.
However, a variety of advanced equipment can also be used to sense stage and measure streamflow. Require an external source of power excitation voltage that provides the majority of the output power of the signal 2 passive sensors. Design and field manual of hydrometry published under hydrology project phase i. The resistor is a direct method of current measurement that ha s the benefit of simplicity and linearity. Pdf a calibration method of current meters researchgate. The velocity of flow at any point in the open channel can be most accurately and conveniently determined by means of a mechanical device named current meter. The ott mf pro is a userfriendly, low maintenance electromagnetic current meter for costefficient instream discharge measurement. To calibrate either of these types of eddy current instruments, certified non. However, large deviations were evident in the discharges measured in the.
The company started making instruments for measuring the speed of the water in londons river thames, since then our product range has grown, but our expertise in current flow measurement remains. By proper consideration of correlations, either type a or type b method of evaluation of uncertainty can be used for evaluation of either random or systematic uncertainty components. This application method is not typically used as it requires both extended plant downtime for system installation and a significant investment in. It does not have a tailfin assembly and is used only for measuring shallow streams with the wading rod. Current meter of common use may be classified in two categories according to the type of revolving. Measurement of threephase power with the 2wattmeter method. Length meter m feet, yard or mile mass kilogram kg lbm, slug or ton time second s electric current ampere a temperature kelvin k rankine, fahreinheit, or celcius amount of substance mole mol luminous intensity candela cd violle. Read this article to learn about the measurement of velocity by current meter. This is known as the twowattmeter method of measuring threephase power. Advantages the most versatile method well established and researched current meters can be accurately calibrated depth and width measurement relatively easy relatively quick and simple disadvantages. The output power is almost entirely provided by the measured signal without an excitation voltage. Download and process s4 current meter data otago marine science. Traceable technique to calibrate current coils for. The current meter method depends on defined channel geometry for the calculation of flow velocities briggs et al.
Mechanical current meters are mostly based on counting the rotations of a propeller and are thus rotor current meters. Classes of current meters several classes of current meters are used in water. Electricity metering systems measure energy consumption, monitor its quality and communicate this information from meter to concentrator or cloud, so that utilities can better manage the use of energy by means of load management. Nov 22, 2015 download and process s4 current meter data otago marine science. This fact is utilized in calibration of the currentmeter. The method is commonly used in initial investigations of potential mini and.
However, the guidelines of master meter method have not been. Current meter is rated in a long tank say 150 m long with sectional area 4 m x 2. A record ice jam in the sl clair river occurred in april 1984 and provide4 an excellent opportunity for testing the current meter program. Measurement of velocity by currentmeter with diagram. Procedure to calculate the uncertainty in a current meter flow measurement. Method of velocity field widespread method for discharge measurement both in open channels and in pipes, standard method for discharge determination in the course of guarantee tests of water machines measurements. Digital multimeters typically have a lcd or led display and in many cases are autoranging. Current electricity multiple choice questions and answers pdf,interview questions,mcqs,lab viva,seminar topics,online quiz important free download. In general, mphase power can be measured by means of m 1 wattmeters. Classification, absolute and secondary instruments, indicating instruments.
The pygmy meter is scaled twofifths as large as the standard type aa current meter. The ekman current meter is a mechanical flowmeter invented by vagn walfrid ekman, a swedish oceanographer, in 1903. This method is well suited for short intake applications where the current meter cm method is the only alternative method. Maintenance efforts of the master meter method are easier than the gravimetric method. If the flow velocity is vf, the meter will align itself in the direction of the resultant velocity vg making an angle. Picking the correct method to monitor current for a given application is critical in optimizing system performance. The current meter is used to measure water velocity at predetermined points subsections along a marked line, suspended cableway, or bridge across a river or stream. Measurement of threephase power with the 2wattmeter. Current status of river discharge observation using non. Time taken ok except for changing flows calculation takes time meters subject. Discharge measurements using a current meter duration.
This fact is utilized in calibration of the current meter. A singlephase meter is used in alternating current systems. It comprises a propeller with a mechanism to record the number of revolutions, a compass and a recorder with which to record the direction, and a vane that orients the instrument so the propeller faces the current. Art its more than just taking readings have to make judgements on how best to make the readings represent what you see streams are dynamic, have everchanging flow patterns we represent complex parameters with straight lines we have to cope with less than ideal conditions. Most meter movements electrostatic movements excepted are quite sensitive, giving fullscale indication at only a small fraction of a volt or an amp. In physics, one distinguishes different reference frames depending on where the observer is located, this is the basics for. A limited number of current meters often 2 are available for gauging at a particular station, usually a. Current in one direction through the wire will produce a clockwise torque on the needle mechanism, while current the other direction will produce a counterclockwise torque. Typical current meter method divide stream cross section into transects 815 total measure velocity in each with meter at 60% depth in shallow water current method. The apparatus differentiates and amplifies incoming dc signals generated by the current meter into both ac and dc signals, which are then sent to a microprocessor. Current meter gauging an art and a science science, ok. Download fulltext pdf proving by master meter method article pdf available in measurement and control london institute of measurement and control. Most of these studies were published before 1960, prior to the development of electromagnetic current meters for stream gaging.
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