1

STUDY ON WATER LEVEL SENSORS

Under the guidance of

Dr. Sai Bhaskar Reddy, Project Co- ordinator,climaAdapt Project,

WALAMTARI, Hyderabad.

SUBMITTED BY,

HAFISA HAMEED

JOMOL T JOSEPH

Water and Land Management Training and Research Institute,

Himayatsagar, Hyderabad - 500030.

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CERTIFICATE

Certified that this project report entitled “STUDY ON WATER LEVEL

SENSORS” is a record of project work done independently by Hafisa Hameed and Jomol T

Joseph under my guidance and supervision and has successfully completed their internship

under ClimaAdapt Project.

30/5/2014 Dr. Sai Bhasker Reddy

Project Coordinator,ClimaAdapt

WALAMTARI, Hyderabad.

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ACKNOWLEDGEMENT

We would like to express our deep sense of gratitude to Dr.Leven K.V Asst.

Professor, Department of Irrigation and Drainage Engineering, K.C.A.E.T., for providing

such an wonderful training opportunity at WALAMTARI. We express our sincere gratitude

to Dr. M. Sivaswami, Dean, K.C.A.E.T, Tavanur for his support during the course of

training.

We thank Dr. Sai Bhasker Reddy for his support, valuable guidance, profound

suggestions, constant backing, prolific encouragement and advice throughout this project

work at WALAMTARI. With deep respect, we sincerely acknowledge, Dr. Yella Reddy, for

providing the necessary information and related data and for the timely help rendered by him.

We express our heartfelt gratitude to Sravanthi, water manager,

WALAMTARI, Pranith, WALAMTARI for providing relevant data and necessary help and

support for field data collection. We offer our hearty thanks to Vanitha ,AE (Irrigation and

CAD Dept.), Ramesh, FTC for their sincere and timely help in getting the necessary

information for the study.

We express our heartfelt thanks to Krishna Reddy for his help extended

towards us in course of this work.

Above all we bow our head before the God Almighty whose blessings

empowered us to complete this work successfully.

HAFISA HAMEED

JOMOL T JOSEPH

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CONTENTS

CHAPTER NO: TITLE PAGE NO:

1 INTRODUCTION 5

2 LITERATURE REVIEW 8

3 SITE SELECTION 10

4 ULTRASONIC SENSORS 15

5 RADAR SENSORS 20

6 MOBILE CANAL CONTROL 25

7 LEVEL DISCHARGE CONVERSION 27

8 DISCUSSION WITH HYDROVISION 29

9 FIELD STUDY 33

10 RESULTS AND DISCUSSIONS 36

11 CONCLUSIONS 42

REFERENCES

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CHAPTER 1

INTRODUCTION

1.1 Level Measurements

Measurement is the estimation of the magnitude of some attribute of an object,such

as its length or weight, relative to a unit of measurement. Measurement usually involves

using a measuring instrument, such as a ruler or scale, which is calibrated to compare the

object to some standard, such as a meter or a kilogram. Measurements are crucial in purposes

such as in science and in engineering. Since accurate measurement is essential in many fields,

and since all measurements are necessarily approximations, a great deal of effort must be

taken to make measurements as accurate as possible.

1.2 Sensor

Sensor or transducers is defined as a device that receives energy from one system

and transmit it to another, like physical variable into signal variable. Broadly defined, the

sensor is a device which capable of being actuated by energising input from one or more

transmission media and in turn generating a related signals to one or more transmission

systems. It provides a usable output in response to specified input measured, which may be

physical or mechanical quantity, property, or conditions. The energy transmitted by these

systems may be electrical, mechanical or acoustical. The nature of electrical output from

the transducers depends on the basic principle involved in the design. The output may be

analog, digital or frequency modulated.

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1.3 Selecting a Sensor

The sensor has to be physically compatible with its intended applications. There

have eights specification that should be considered while selecting a sensor.

1) Operating range: Chosen to maintain range requirements and good resolution.

2) Sensitivity: Chosen to allow sufficient output.

3) Frequency response and resonant frequency: Flat over the entire desired range.

4) Environment compatibility: Temperature range, corrosive fluids, pressure, shocks,

interaction, size and mounting restrictions.

5) Minimum sensitivity: To expected stimulus, other than measured.

6) Accuracy: Repeatability and calibration errors as well as errors expected due to sensitivity

to other stimuli.

7) Usage and ruggedness: Ruggedness, both of mechanical and electrical intensities versus

size and weight.

8) Electrical parameters: Length and type of cable required, signal to noise ratio when

combined with amplifiers, and frequency response limitations.

1.4 Types of Level Measurement Sensors.

Various systems in sensors developments have been introduced to assist in crucial

measurements of level. These sensors are most likely incorporates business obligation though

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there are certain sensors provided for non-business or profitable usage and for the usage in

education purposes. There are many physical and application variables that affect the

selection of the optimal level monitoring solution for industrial and / or commercial

processes. Selection is categorized to contact and non-contact sensor. The selection criteria

include the physical: state (liquid, solid or slurry),temperature, pressure or vacuum,

chemistry, dielectric constant of medium, density or specific gravity of medium, agitation,

acoustical or electrical noise, vibration, mechanical shock, tank or bin size and shape; and the

application constraints: price, accuracy, appearance, response rate, ease of calibration or

programming, physical size and mounting of the instrument, monitoring or control of

continuous or discrete (point) levels. The selection criteria selected in this project is non-

contact point level detection or continuous monitoring of solids and liquids. The sensor types

to assist in this particular criterion are as follows:

i. Capacitance level sensor (also called RF)

ii. Ultrasound

iii. Radar

iv. Mobile Canal Control

v. Electromagnetic sensor

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CHAPTER 2

LITERATURE REVIEW

Agricultural land management practices are compatible with the preservation of

water resources. Hydrological diagnoses are needed in order to choose the alternative land

uses, cultivation practices and/or their spatial arrangements (Pandey et.al;)

The monitoring water level in a river or in a reservoir is important in the

applications related to agriculture, flood prevention, and fishing industry, etc. The schemes

developed for measuring water level can be categorized as four types based on the measuring

features: pressure, supersonic waves, heat, and image( Jaehyoung Yu and Hernsoo Han).

Human supervision is limited for several hours and the accuracy is almost not

perfect. Sensors introduces a better solution in accurate level measurements and automatic

processing of water levels (Muhd Asran Bin Abdullah).

According to Dana Gardner,By the year 2000, 50% of all engineers will

design with sensors, up from 16% who routinely used them at the beginning of the decade.

”

Although pressure sensor is easy to use, it has a limitation that it should be

calibrated and replaced frequently due to possible breakdown by continuous water pressure.

Supersonic wave sensor is free from water pressure since it measures the time of travel of

supersonic wave pulse from emitter to receiver reflected by the water surface (. B. Y. Lee and

B. Y. Park).

Use of image sensor for measuring water level is the most recent approach.

Different from other types of sensors, it can provide the surrounding information around the

sensor as well as the water level so that the measured data can be confirmed. It also has

an advantage that it is unaffected by weather (Kon et.al;)

Commenting on his experience with the radar sensor the Environment

Agency's Rikk Smith says, 'We have been very pleased with this sensor because it was quick

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and easy to install and we have not had to touch it since it was installed over five months

ago.”

Ultrasound echo ranging transducers can be used in either wetted (contact) or

non wetted (non-contact) configurations for continuous measurements of liquid level. An

interesting application of wetted transducers is as depth finders and fish finders for ships and

boats. Non wetted transducers can also be used with bulk materials such as grains and

powders (Jerry C.Whitaker),

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CHAPTER 3

SITE SELECTION

This section contains information on site selection based on NEMS (National

Environmental Monitoring Standards). It primarily covers the site related variables to

consider when selecting a site. Ensure that the stationarity, accuracy and operating

requirements laid out in this standard are met. By selecting the best available site and/or

installing the best available control structure, data quality will be maximised and work

minimised over the period of the record. The following standards can be found at

www.landandwater.co.nz.

3.1 SOURCES OF INFORMATION

The following sources of information should be used to determine the most

appropriate stretch of river or shoreline (site) for deploying a station:

advice (where available) on access, stability and history

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3.2 PRACTICAL CONTROLS

Satisfactory natural controls are often difficult to find because topography,

geology, and the range and frequency of flows. For instance, gorges cut through bedrock

provide better control sites than riverbeds on alluvial plains. Purpose-built artificial controls

can often provide a stable rating for a small stream site. Where practicable, an existing natural

or artificial control can be altered to improve its sensitivity or stability. The means of doing

this will vary according to the site and other factors.

3.2.1 Safety

Hazards (for observers, the public, livestock, and wildlife) related to the

location and the measurement activity shall be identified and mitigated.

3.2.2 Hazard Review

On selection of a final site, a hazard review shall be carried out in accordance

with relevant guidelines or best practise.

3.2.3 Stationarity of record

It is maintained when variability of the parameter being measured is only caused by

the natural processes associated with the parameter, and ceases when variability is caused or

affected by other processes, moving the station, or adjusting the recording zero height of the

station’s reduced level. Without stationarity, a data record cannot be analysed for changes

over time (such as climate change). While the accuracy of collection processes may change, it

is critical that the methods and instruments used to collect water level record remain without

bias over the lifetime of the record.

3.3 LEVEL STATIONS

The following aspects shall be considered when selecting a site on a reservoir or

lake.

3.3.1 Access and Legal Requirements

The following access issues of a site shall be considered:

Site safe access over the full anticipated range to be measured

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the ability to position machinery and materials during construction

. Safe access is required for reading staff gauges and to carry

out flow measurements

A long-term access agreement with any landowners whose land must be crossed to gain

access to the site

3.3.2 Installation

Aspects to be considered shall include, for example:

Public safety and site security

Constructability and durability. (In particular, consider protection from flood or wave

damage.)

needs to be solid.

Permanent benchmarks should be present.

An adequate power supply from solar, mains or other power sources

Adequate communication for telemetry

3.3.3 Stability for site

Where practicable, one or more of the following features that are relatively resistant

to erosion shall be present as a control:

constriction in the channel between non-erodible banks

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Where practicable, the following features shall be avoided:

Control that is likely to be affected by vegetal growth on the beds and banks

shall be avoided, or its effects mitigated by weed control measures. Also a control that is

likely to be affected by human interference shall be avoided.

3.4 DEPLOYMENT

Once a site has been selected, the design and construction of the installation type and

deployment of equipment follows. Planning a station requires consideration of a number of

factors that can affect the quality, availability and long-term usefulness of the data that is

collected.

These factors are:

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Safe and convenient access to recording stations is crucial for data

collection. Where permission shall be obtained for access over and installation of equipment

on land, whether private, local authority, corporate or government owned. It may be useful to

precede construction work with a site survey for the purposes of design. At the least, a station

history form should be filled out for the site as soon as records begin, updated following

changes, and checked during the annual site inspection

All materials used in installations shall be of adequate strength, thickness

and durability for the purpose. Generally:

Timber should be treated against rot to an appropriate specification (or better)

-dip galvanised or stainless steel

Security gates or systems shall be installed for the safety of anyone who

visits the vicinity, and to protect the station from vandalism. And also to protect installations

vulnerable to interference and damage, including deliration from flora and fauna.

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CHAPTER 4

DETAILED STUDY OF DIFFERENT SENSORS - ULTRASONIC

SENSORS

4.1 INTRODUCTION

Ultrasonic level sensors are used for non-contact level sensing of highly

viscous liquids, as well as bulk solids. They are also widely used in water treatment

applications for pump control and open channel flow measurement. The sensors emit high

frequency (20 kHz to 200 kHz) acoustic waves that are reflected back to and detected by the

emitting transducer.

Ultrasonic level sensors are also affected by the changing speed of sound

due to moisture, temperature, and pressures. Correction factors can be applied to the level

measurement to improve the accuracy of measurement. Turbulence, foam, steam, chemical

mists (vapours), and changes in the concentration of the process material also affect the

ultrasonic sensor’s response. Turbulence and foam prevent the sound wave from being

properly reflected to the sensor; steam and chemical mists and vapours distort or absorb the

sound wave; and variations in concentration cause changes in the amount of energy in the

sound wave that is reflected back to the sensor. Wave guides are used to prevent errors

caused by these factors.

Proper mounting of the transducer is required to ensure best response to

reflected sound. Since the ultrasonic transducer is used both for transmitting and receiving the

acoustic energy, it is subject to a period of mechanical vibration known as “ringing”. This

vibration must attenuate (stop) before the echoed signal can be processed. The net result is a

distance from the face of the transducer that is blind and cannot detect an object. It is known

as the “blanking zone”, typically 150mm – 1m, depending on the range of the transducer.

The requirement for electronic signal processing circuitry can be used to

make the ultrasonic sensor an intelligent device. Ultrasonic sensors can be designed to

provide point level control, continuous monitoring or both. Due to the presence of a

microprocessor and relatively low power consumption, there is also capability for serial

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communication from to other computing devices making this a good technique for adjusting

calibration and filtering of the sensor signal, remote wireless monitoring or plant network

communications. The ultrasonic sensor enjoys wide popularity due to the powerful mix of

low price and high functionality.

4.2 PRINCIPLE OF MEASUREMENT

An ultrasonic level transmitter is fixed at the top of a tank half filled with liquid. The

reference level for all measurements is the bottom of the tank. Level to be detected is marked

as “C”, and “B” is the distance of the ultrasonic sensor from the liquid level. Ultrasonic pulse

signals are transmitted from the transmitter, and it is reflected back to the sensor. Travel time

of the ultrasonic pulse from sensor to target and back is calculated. Level “C” can be found

by multiplying half of this time with the speed of sound in air. The measuring unit final result

can be centimetres, feet, inches etc.

Level = Speed of sound in air x Time delay / 2

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Ultrasonic Sensor is the heart of the ultrasonic level Transmitter instrument. This

sensor will translate electrical energy into ultrasound waves. Piezoelectric crystals are used

for this conversion process. Piezoelectric crystals will oscillate at high frequencies when

electric energy is applied to it. The reverse is also true. These piezoelectric crystals will

generate electrical signals on receipt of ultrasound. These sensors are capable of sending

ultrasound to an object and receive the echo developed by the object. The echo is converted

into electrical energy for onward processing by the control circuit.

4.3 PRACTICAL LIMITATIONS

a. Velocity of sound changes due to the variation of air temperature. An integrated

temperature sensor is used to compensate for changes in velocity of sound due to temperature

variations.

b. There are some interference echoes developed by the edges, welded joints etc. This is

taken care by the software of the transmitter and called interference echo suppression.

c. Calibration of the transmitter is crucial. Accuracy of measurement depends on the

accuracy of calibration.

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4.4 FUNCTIONAL BLOCK DIAGRAM OF A TYPICAL ULTRASONIC

LEVEL TRANSMITTER

A micro-controller based Control Circuit monitors all the activities of the

ultrasonic level transmitter. There are two Pulse Transmission Circuits, one for transmitter

pulse and the other one for receiver pulse. The pulse generated by the transmitter pulse is

converted to Ultrasound pulses by the Ultrasonic Sensor (Transmitter) and targeted toward

the object. This ultrasound pulse is reflected back as an echo pulse to the Ultrasonic Sensor

(Receiver). The receiver converts this Ultrasonic pulse to an electrical signal pulse through

the pulse generator. The time elapsed, or the reflection time is measured by the counter. This

elapsed time has relation to the level to be measured. This elapsed time is converted to level

by the Control Circuit. There is a Timing Generator Circuit which is used to synchronize all

functions in the ultrasonic level measurement system.

The level is finally converted to 4-20mA signal. 4mA is 0% level, and 20mA is

the 100% level. This 4-20mA output signal carrying the level data can be transmitted to long

distance to Process Control Instruments.( 4-20mA output signal depends on model. It may

vary according to manufacturers.)

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4.5 ADVANTAGES OF ULTRASONIC SENSORS

Ultrasonic level transmitter has no moving parts, and it can measure level

without making physical contact with the object. This typical characteristic of the transmitter

is useful for measuring levels in tanks with corrosive, boiling and hazardous chemicals. The

accuracy of the reading remains unaffected even after changes in the chemical composition or

the dielectric constant of the materials in the process fluids.

4.6 LIMITATIONS

Ultrasonic level transmitters are the best level measuring devices where the

received echo of the ultrasound is of acceptable quality. It is not so convenient if the tank

depth is high or the echo is absorbed or dispersed. The object should not be sound absorbing

type. It is also unsuitable for tanks with too much smoke or high density moisture.

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CHAPTER 5

DETAILED STUDY OF DIFFERENT SENSORS - RADAR

SENSORS

5.1 INTRODUCTION

Radar technology is mainly put into use for detection of level in continuous level

measurement applications. Radar level transmitters provide non contact type of level

measurement. They make use of EM i.e. electromagnetic waves usually in the microwave X-

band range which is near about 10 GHz. Hence, they can be also known as microwave level

measurement devices

A radar level detector basically includes:

A transmitter with an inbuilt solid-state oscillator

A radar antenna

A receiver along with a signal processor and an operator interface.

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5.2 PRINCPLE OF OPERATION

Working principle of radar sensor is similar to ultrasonic sensors. The operation of all

radar level detectors involves sending microwave beams emitted by a sensor to the surface of

liquid in a tank. The electromagnetic waves after hitting the fluids surface returns back to the

sensor which is mounted at the top of the tank or vessel. The time taken by the signal to

return back i.e. time of flight (TOF) is then determined to measure the level of fluid in the

tank.

5.3 TYPES OF RADAR SENSORS

5.3.1 GUIDED WAVE RADAR

In this method, a cable or rod is employed which act as a wave guide and

directs the microwave from the sensor to the surface of material in the tank and then straight

to its bottom. “The basis for GWR is time-domain reflectometry (TDR), which has been used

for years to locate breaks in long lengths of cable that are underground or in building walls. A

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TDR generator develops more than 200,000 pulses of electromagnetic energy that travel

down the waveguide and back.

The dielectric constant of the process material will cause variation in impedance and reflects

the wave back to the radar. Time taken by the pulses to go down and reflect back is

determined to measure level of the fluid.

In this method, the degradation of the signal in use is very less since

the waveguide offers extremely efficient course for signal travel. Hence, level measurement

in case of materials having very low dielectric constant can be done effectively. Also in this

invasive measurement method, pulses are directed via a guide; hence factors like surface

turbulence, foams, vapors or tank obstructions do not influence the measurement. GWR

method is capable of working with different specific gravities and material coatings.

However, there is always a danger that the probe or rod used as a waveguide may get

impaired by the agitator blade or corrosiveness of the fluid under measurement. A typical

guided wave radar system is shown in the figure below.

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5.3.2 THROUGH AIR RADAR SYSTEM

They usually employ a horn antenna or a rod antenna for sending

microwave beams onto the surface of the liquid being measured. These antennas mounted at

the top of the tank then receive the reflected microwave signal back from the fluid surface. A

timing circuit is incorporated in the systems which measures the time of flight and hence the

distance between the antenna and the fluid level is determined. These systems can pose

measurement problems if the dielectric constant of the fluid being measured is very low.

“The reason is that the amount of reflected energy at microwave (radar) frequencies is

dependent on the dielectric constant.

5.4 ADVANTAGES

Major advantages of radar level detectors include:

Radar level measurement technique offer extremely accurate and reliable detection of

level in storage tanks and process vessels.

The performance of radar level transmitters remains unaffected by heavy vapors and

mostly all other physical properties of the fluid under level measurement (except

dielectric constant of the liquid).

5.5 DISADVANTAGES

Radar level measurement systems incorporate following drawbacks:

Major disadvantage associated with radar level detectors is their high cost.

Besides, these systems are not capable of detecting level between interfaces.

Also their pressure ratings are very restricted.

In case of pulse radar, one usually faces problem in getting accurate measurement results

if the fluid being measured is very near to the radar antenna. Since, in that case the time

taken by the signal to travel between sensor and process material will be very fast i.e. not

adequate for accurate determination of level.

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These devices work well with light layer of dirt and dust only. In situations where the

layer of dust or foam gets substantial, they cease to detect the fluid level. Therefore, in

dirty applications the radar level detectors gets replaced by ultrasonic level detectors.

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CHAPTER 6

DETAILED STUDY OF DIFFERENT SENSORS- MOBILE

CANAL CONTROL

6.1 INTRODUCTION

A recent innovation called The MobileTracker can be seen as the

next generation of semi-automatic measurement devices. the MobileTracker is made for the

smart-phone and uses the telephone’s camera and special pattern-recognition software. This

technology makes manual data entry of water variables unnecessary With MCC it is possible

to perform accurate measurements and control of irrigation canals by using smartphones.

The procedure for taking measurements is as simple as taking a photo with a smart-phone. It

can thus also be used by less experienced personnel. In exceptional circumstances it could

even be used by farmers in remote areas or students passing a stream on their way to school.

The only requirement is a smart-phone.

6.2 WORKING

The Mobile Tracker works as follows: When a field operator arrives at a

location, they take the smart-phone and start an application that makes contact with the

central database. The application uses the GPS coordinates and angles of the smart phone to

identify the location and store all the relevant data. For water level measurements these

would usually be the reference level, subsidence of the staff gauge and known impairments

of the staff gauge. For flow measurements these are, for example, width of the gate and

calibration coefficient. For ground water measurements it is the level of the top of the

groundwater pipe. With one click on the app, a photo is taken and from the photo water

variables such as water level, flow and groundwater level can be measured. These values are

then sent to a database and saved including information pertaining to location with a time

check, the field operator on duty, GPS coordinates and camera angles. The photo is also sent

and saved with the other information. The advantage of this procedure is that is faster than

manual data and no data errors can be made. Because the photo is saved, it can be referred to

afterwards using the correct photo at the right place and at the right time to verify concerns

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about inaccurate readings or disputes about a presumed situation. The central system can be

managed from FEWS. The Mobile Tracker is also connected to WISKI and Aquarius.

Methods are available for measuring water levels, gate positions/flows and ground water

levels.

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CHAPTER 7

LEVEL TO DISCHARGE CONVERSION

To transform a water level to water discharge, there are four practical ways:

(i) to measure the flow velocity at the same time as water level

(ii) to use some particular hydraulically controlled section

(iii)to use pre-calibrating rating-curves and

(iv) to use the mean empirical Gauckler-Manning-Strickler law ( simply denoted hereinafter

as Manning’s equation.)

The three first ways need additional heavy sensors or equipments and,

long-term studies under flow conditions. In a given cross-section of a channel, the water level

can be converted to water discharge using the widely used Manning equation. The Manning

equation was developed empirically in laboratory channels with optimal draining conditions

and uniform flow and no downstream influences must be assumed to apply the equation.

However due to lack of a better solution, it is assumed that the equation is also valid for non-

uniform reaches that are invariably encountered in natural channels if the energy gradient is

modified to reflect only the losses due to boundary friction .

The instantaneous flow velocity v [m.s−1

] and discharge Q [m3.s

−1] in a

channel are estimated as follows:

v= 1/n R 2/3

S 1/2

Q= v . A

where S [dimensionless] denotes the slope of the water surface, which can be approximated

by the slope of the channel.

As slope and cross-section shape being temporally stable, it can be both

estimated from topographic ground survey. The hydraulic radius depends on water level

which is measured by the stage recorder. The term n can be estimated by choosing, in the

abundant literature, the most suitable coefficient, according to cross-section characteristics

(dimensions and shape), bed substrate and cover types (vegetation, concrete, plastic, etc.).

Assuming that Manning’s equation is relevant, the uncertainty in discharge estimation comes

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mainly from the uncertainty around n, i.e., possible values for this parameter. Indeed,

vegetation is a primary factor in the increase of the roughness and resistance in channels.

Hence, a maximum value should be used during periods of low flows and high vegetation

density, and minimum values during high flows and low vegetation density. Therefore,

discharge estimation is associated to an envelope curve which corresponds to an upper and a

lower acceptable limits on discharge estimation. Hence, when the water level sensor is

installed at a catchment outlet, discharge could be estimated with a given uncertainty and

several indicators could be derived to characterize catchment hydrological behaviour.

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CHAPTER 8

“CHALLENGES IN OPEN CHANNEL DISCHARGE

MEASUREMENT AND VARIOUS SOLUTIONS USING AREA

VELOCITY METHOD”

(Discussion with representatives of HYDROVISION)

8.1 TYPICAL VELOCITY DISTRIBUTIONS FOR SEVERAL

CHANNEL PROFILES

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8.2 TYPES OF ULTRASONIC MEASUREMENT TECHNOLOGY

8.2.1 CONTINUOUS WAVE DOPPLER

Continuous wave (CW) Doppler is the older and electronically more simple

of the two kinds. As the name implies, CW Doppler involves continuous generation of

ultrasound waves coupled with continuous ultrasound reception. A two crystal transducer

accomplishes this dual function.

The main disadvantage of CW Doppler is its lack of selectivity or depth

discrimination. CW Doppler measurements are a spot velocity measurement. The sensor is

not able to determine at which level the velocity has been detected. Due to this reason the

flow profile cannot be represented.

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8.2.2 DIGITAL PULSED DOPPLER

Pulsed wave (PW) Doppler systems use a transducer that alternates

transmission and reception of ultrasound. One main advantage of pulsed Doppler is its

ability to provide Doppler shift data selectively from a small segment along the ultrasound

beam, referred to as the “sample volume”. The location of the sample volume is operator

controlled.

CLASSIFICATION OF DIGITAL DOPPLER

8.3 WATER LEVEL MEASUREMENT

>Bubbler

>Hydrostatic

>Shaft Encoders

>Ultrasonic

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>Radar

>Optical /Video processing

Nowadays Bubbler and Shaft encoders are not in use. New technologies

using radar and ultrasonic waves are now prominent in market. Both ultra-sonic and radar

sensors have non-contact type models.

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CHAPTER 9

FIELD STUDY

9.1 LOCATION

Mirialaguda DC 4 circle irrigation canal systems were studied.

9.2 OBSERVATIONS

>Major canals can be automated using high precision sensors; installed along various site

identified.

> Some portion of the canals were unlined. Lining activity is carried out in certain places

of Wazeerabad (L5 major).

> Canals were not maintained properly; wastes and rocks were dumped.

> Cross section of the canals were not constant, especially the minor canals.

> Farmers are unaware of sensors and water level automation system.

>Permanent structures over canals were identified. (Annexure 1).

Plate 1: L5 major Wazeerabad

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Plate 2: DROP 1 at L5 major (Q = 0.87 C/s)

Plate 3: PIPE NO.1 (0.27 Km from L5 Major)

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Plate 4: L6 Minor of Wazeerabad Major

Plate 5: Unlined canal with varying cross section

36

CHAPTER 10

RESULTS AND DISCUSSION

10.1 SENSOR EVALUATION

SENSORS

WATER

LEVEL

ACCURACY

POWER

INPUT

COST/UNIT

(Rs)

SERVICE OF

AGENCY

1) CAMPBELL

SCIENTIFIC

1 year warranty

>RADAR RANGING SENSOR 4275-72585

a)CS475-L 50mm-

20m

± 5mm 9.6-16

Vdc

b)CS476-L 50mm-

30m

±3mm 9.6-16

Vdc

c)CS477-L 400mm-

70m

±15mm 9.6- 16

Vdc

>SONIC RANGING SENSOR 2565-55285

SR50A-L 0.5-10m ±1cm 9-18 Vdc

2) VIRTUAL

ELECTRONICS

>DIGITAL WATER LEVEL RECORDER-RADAR

TYPE

30210-60125

DWLR-R 15m-70m ±2mm 12 v

3)

HYDROVISION

>ULTRASONIC LEVEL

SENSOR

2575-50254

SEP3702 25m ±2% 24 Vdc

SHANGHAI

CX-RLM RADAR

WATER LEVEL

SENSOR WITH

ALARM

30 m <0.1% 4216-60230 1Year warranty

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10.2 SENSOR SELECTION

Based on the study on different sensors, radar sensors was found to be

more accurate when compared to ultrasonic because

In flow measurement of open channels, the flow measurement error of

ultrasonic sensors, due to temperature error, can amount to more than 20 %.

Local authorities and individual companies will calculate their costs based

on this measurement data, so substantial differences can arise in their

accounting.

Since radar is independent of external weather conditions such as rain, solar

radiation, wind or fog, radar measurement is actually the more suitable

alternative.

Another consideration is that adjustment and operation of radar instruments

has become very easy.

4) CHEMINS

WATER LEVEL

SENSOR LKZLD-A

30 m <0.1% 24 Vdc

RADAR WATER

LEVEL SENSPOR

HD

30 m 6000-12000

5) SHANGHAI

CX-RLM-081

PULSE RADAR

INFRARED

WATER LEVEL

SENSOR

20m <0.1% 7000-60230

RRF-15 70m ±5mm 60230-18690

VRPWRD51-56 20m ±10mm 48184-12460

VRPWRD35 20m ±3mm 24 Vdc 48184-12460

SHAANXI CHINA-RADAR WATER LEVEL

SENSOR

YK=RLT01 35m ±2mm 6023-72276

38

The benefits for users include high accuracy, high reliability, ease of use

and low costs. Previously, the price difference between radar and ultrasonic

instrumentation was very high; today, the price of radar is comparable to

that of ultrasonic.

When considering about large scale installation of sensors there will be a

great variation in cost among radar and ultrasonic. Ultrasonic sensors can be used

successfully in places were temperature variation is less. Temperature sensitivity of sensor

depends on the modl and the manufacturers. Usually they operate between -2 to 45 0 C.

Canals Sensors Type Description Average cost

for complete

installation(Rs)

Installation

Major RADAR Non-

contact

Highly accurate but

coastlier

30000- 60500 Stand alone

poles or by

providing

extension

hangings

39

Major ULTRASONIC Non-

contact

Accurate but

depends on

temperature

variation

15670- 35000 Stand alone

poles or by

providing

extension

hangings

Major Digital doppler Contact Measures velocity

also

6000 – 30000 Mounted to

canal sides

Minor Digital doppler Contact Measures velocity

also

6000 – 30000 Mounted to

canal sides

Minor Pressure sensor Contact Based on weight of

water

5000-25000 Submerged in

canals

Minor Staff guages Contact Human recording 1000 Mounted

along canal

sided

10.3 SITE SELECTION

Permanent structures were sensors can be mounted in field were

evaluated (bridges and drops).

STRUCTURES

DISTANCE FROM

WAZERABAD MAJOR

CHILLAPUR BRIDGE 0.910 km

DILVARPUR BRIDGE 4.68 km

DILWAPUR S.L BRIDGE 10.22 km

S.L BRIDGE 13.20km

S.L BRIDGE 14.80 km

DROP CUM S.L BRIDGE 11 16.977 km

DROP CUM S.L BRIDGE 14 18.41 km

40

Sensors can be installed economically either beneath the bridges or on drops. Cost can be

reduced by providing small poles clamped to the upstream side of drops with an extension

across the canal. The data of drop structures of Wazerabad major includes

DROP NO: 1 0.914 Km

DROP NO: 3 8.045 Km

DROP NO: 5 11.529 Km

DROP CUM REGULATOR 8 15.690 Km

DROP NO: 12 17.160 Km

DROP NO: 16 20.589 Km

DROP CUM REGULATOR 23 22.433 Km

DROP NO: 25 23.622 Km

Sensors can be mounted approximately in these positions considering the environmental

conditions and human interferences.

10.4 FIELD CHALLENGES

Farmers are unaware of sensors and its applications. They should be made

aware about sensors and its uses.

Non- continuous flow through canal causes periodic removal and

installation of sensors.

Chance of theft is higher

Providing human security will increase the cost of level measurement

project.

Provision of security gates and periodic inspection of sensors are

recommended.

41

10.5 SENSOR SUPPLIERS IN MARKET

There are many sensor suppliers in market. We contacted them and

broachers were collected.

HYDROVISION ram.warriar@hydrovision.de

VIRTUAL ELECTRONICS athul@virtualweb.co.in

CAMBELLSCIENTIFIC Krishna.Kishora@elcometech.com

JAYCEETECH jayceetech@vsnl.net

PROTOCOL INSTRUMENTS Sales@baseelectronics.in

A number of other industries were contacted through online Shoppe (CHEMIN,

SHANGHAI etc. ).

42

CHAPTER 11

CONCLUSIONS

Agricultural land management practices should compatible with the

preservation of water resources. Hydrological diagnoses are needed in order to choose the

alternative land uses, cultivation practices etc. The proposed hydrological strategy for open

channel monitoring is based on the study on different sensors and its limitations. Low cost

and energy consumption optimization of the proposed sensor allows one to multiply it in

space and to transmit data to any places required. Moreover, its design and properties (handy,

easy to install and uninstall, low-cost, etc.) make the proposed sensor mobile and soft, which

allow one to simultaneously monitor level with high resolution.

Among the various non-contact sensors studied, radar sensors are found to give high

resolution data. Based on economic considerations, ultrasonic sensors stand ahead of

the radar sensors. Budjet of the project place a major role in selection among radar

and ultrasonic sensors in major canal. Since minor canal requires less accuracy than

major canal, contact Doppler can be used.

Permanent structures like bridges are found to be best suited for sensor installation. It

reduces the cost of long poles and foundations.

Sensors can also be installed successfully on drops; an extension to be provided

across the channel.

The present field situation does not allow to left back the sensors in field. Periodic

monitoring and security system should be provided to prevent theft and to ensure

proper working of the monitoring system.

Based on evaluation of different sensor suppliers, HYDROVISION and CAMPELL

SCIENTIFIC were found to provide wide varieties and compact model of sensors.

They also provide good service facilities.

Further studies should be conducted to study about sensors and the data processing

systems.

43

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