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. With current metering the rotation of a current meters impeller figure 1 gives the local water velocity following application of a calibration equation called a rating equation. In centrifugal pump applications, electrical power is measured using electrical and mechanicalelectrical methods. 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.
Considering geh total area to be divided info n1 segments. Interpreting the 50 microampere scale illustration on next page the black arc that is labeled dc second from top is used for. It basically works on the principle of bernoullis theorem. The total discharge is calculated be the method of midsections as follows. If the flow velocity is vf, the meter will align itself in the direction of the resultant velocity vg making an angle. Not only does the model 928a measure basic data and power quantities, but it also measures power quality including harmonics, flicker, sags, surges and interruptions. The initial results showed an overall mean difference between the two methods that was very low. These may be due to bias errors in the equipment used for calibration and measurement, or to random scatter caused by, for example, a lack of sensitivity of the equipment used for the measurement.
This cannot be corrected, so the more accurate current metering method is recommended. The method is commonly used in initial investigations of potential mini and. Watts current technical bulletin measuring resistance. 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. Prodtest details from your electric supplier account number customer name service address.
To view pdf documents, you must have the adobe acrobat reader free from adobe systems installed on your computer. If you have adobe acrobat reader installed on your computer, you may view andor print the pdf version of this report. Area velocity method calculation of discharge figure 4. In addition the upper span on a number of these meters will range into kilohms, which covers the lower ranges of a wheatstone bridge please see the appendix for a. In addition to this method of damping, which comes from the movement itself, most meters use a second method of damping. Gratitude goes to each person involved in the preparatio n. If you do not have acrobat reader, you may download it here.
Many studies of currentmeter performance have been conducted by researchers thibodeaux, 1992. More often, the generated current is rectified and measured by a moving coil meter. The uncertainty in a current meter measurement sciencedirect. Operating instructions acoustic, digital current meter.
In an effort to keep these methods consistent with current technology, method to11 has been revised and update d as method to11a in this compendium to incorporate new or improved sampling and analytical technologies. Handheld metal detectors for use in concealed weapon and. Pdf a calibration method of current meters researchgate. The cup wheel rotates due to relative velocity between water and the cup wheel. Notice in illustration a that the ammeter actually becomes part of the circuit that.
Typical current meter method divide stream cross section into transects 815 total measure velocity in each with meter at 60% depth in shallow water sep 25, 2015 current measurement using multimeter. Compendium of methods for the determination of toxic. Pdf current meter calibration and threedimensional. In this method, a source current of constant and known amperage flows across the load under test. Sesdproc106r4, field measurement of dissolved oxygen, replaces sesdproc106r3. Pdf this paper presents a rapid method for propeller current meter calibration, enabling. The reference design uses different switchable shunt resistances, which are switched on in a sequence to measure the insulation resistance. A fairly new method called the acoustic scintillation flow measurement asfm has been used and compared to the cm method.
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. The conductivity meter then uses the conductance and cell constant to display the conductivity. The method is valid for both balanced and unbalanced circuits with either the load or the source unbalanced. 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. It is required to calculate the uncertainty in a current meter gauging from the following particulars. All measurements of physical quantities are subject to uncertainties. The multimeter simultaneously measures the voltage across the load and employs. Most of these studies were published before 1960, prior to the development of electromagnetic current meters for stream gaging. Pdf the paper presents experiences gathered during many years of utilizing the currentmeter and pressuretime methods for flow rate measurements in. Distortions introduced by measurement a ammeter the resistor r is shown by rectangle here to emphasize that the method can be. Current meter calibration and threedimensional displacement effects article pdf available in journal of hydraulic research 205. To apply 256bit aes encryption to documents created in acrobat 8 and 9, select acrobat x and later. Introduction to measurement methods discharge computations by. Current meters and open channel meters have been a speciality of valeports since the company was first formed in 1969.
In general, mphase power can be measured by means of m 1 wattmeters. Many studies of current meter performance have been conducted by researchers thibodeaux, 1992. A current meter is oceanographic device for flow measurement by mechanical, tilt, acoustical or electrical means. Both the current and the potential are used to calculate the conductance iv. Measurement of threephase power with the 2wattmeter. This induced current will act to damp oscillations.
Reading the pdf propertiesmetadata in python stack overflow. Vc mto rms f 73 for a constant angular frequency to, the current is proportional to the applied voltage v. This fact is utilized in calibration of the currentmeter. The speed of rotation of the cup wheel is a function of the velocity of flow. 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. The advent of the acoustic doppler current profiler adcp made possible the development of a dischargemeasurement system capable of more accurately measuring unsteady or tidally affected flow. If the flow velocity is vf, the meter will align itself in the direction of the resultant. Low resistance ohmmeters are designed specifically for these applications.
A limited number of current meters often 2 are available for gauging at a particular station, usually a. Total circuit current must then flow through the meter. Current meter is rated in a long tank say 150 m long with sectional area 4 m x 2. The second method of damping used in most meter movements is an airtight chamber. Let the resistance of the element x be r the actual circuit current is i v br after insertion of the ammeter, the total circuit resistance changes and so does the current.
Electric meter read for 03212018 04072018 17 days read type meter number current meter read previous meter read read difference multiplier usage total kwh 0. The leakage current is measured by applying a fixed voltage and measuring the voltage across the shunt that is a result of the leakage current. This paper presents a rapid method for propeller current meter calibration, enabling calibration of current meters in their actual working conditions using simpler equipment than what is currently. Interpreting the 50 microampere scale illustration on next page the black arc that is labeled dc second from top is used for taking all dc current measurements. The resistor is a direct method of current measurement that ha s the benefit of simplicity and linearity. Measurement of threephase power with the 2wattmeter method.
Electrical power measurement is a method of measuring the power in a circuit, which is expressed in watts. Comparison of discharge measurement by current meter and. This is known as the twowattmeter method of measuring threephase power. In addition, any references to former division organizational structure was updated to reflect current structure. Pdf the comparative analysis of the currentmeter method and the.
Time taken ok except for changing flows calculation takes time meters subject. This method is well suited for short intake applications where the current meter cm method is the only alternative method. This method is the result of the efforts of many individuals. 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. Yarnell and naglers 1931 study on mechanical current meters is one often referenced. A venturi meter may also be used to increase the velocity of any type fluid in a pipe at any particular point. The manual concentrates on the current meter streamflow measurement by wading. Exposure time of current meter at each of 2 points. Both ac and dc currents can be measured with a multimeter by connecting the meter in series with the circuit, in which current being measured provided the current in that circuit is limited or controlled by a load or appropriate values of resistance. Use ofcurrent meters for continuous measurement offlows in. A record ice jam in the sl clair river occurred in april 1984 and provide4 an excellent opportunity for testing the current meter program.
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. Current meter gauging an art and a science science, ok. Higher values may be obtained with dilution of the sample. Corrected any typographical, grammatical, andor editorial errors. In most cases, an adcp dischargemeasurement system is dramatically faster than conventional dischargemeasurement systems and has comparable or better. In all other cases, the method returns files that exactly match the specified extension. Current files with extensions that begin with the specified extension. The ott acoustic digital current meter adc is a mobile acoustic current meter. Measurement of velocity by currentmeter with diagram. Every day, throughout the world, numerous current meter measurements are made in open channels to measure flow without any report. Users with visual disabilities can visit this site for conversion tools and information to help make pdf files accessible. Compendium of methods for the determination of toxic organic. This fact is utilized in calibration of the current meter.
In physics, one distinguishes different reference frames depending on where the observer is located, this is the basics for. The subject of river discharge measurements is vast and complex and this manual do not pretend to comprehensively explore it. The velocity averaged over the vertical at each section is known. The method is commonly used in initial investigations of potential mini and small hydropower sites.
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. Model 928a power system multimeter power measurement series. Merge convert multiple pdf files into one pdf stack overflow. Adc ott acoustic digital current meter insruction manual.