monitoring and control of basicparameters of electroplating industry
DESCRIPTION
Monitoring and Control of BasicParameters of Electroplating IndustryTRANSCRIPT
i
Monitoring and Control of BasicParameters of electroplating industry
Table of Contents
Abstract..................................................................................................................................iii
CHAPTER 1...............................................................................................................................1
INTRODUCTION.......................................................................................................................1
1.1 INTRODUCTION........................................................................................................................................2
1.1.1 Electroplating Industry.................................................................................................................2
Figure 1.1-Electroplating Industry Setup...................................................................................2
Figure1.2-View of an Electroplating System.............................................................................3
1.1.2 System under our consideration..................................................................................................5
1.2OBJECTIVE...............................................................................................................................................5
1.3 SCOPE...................................................................................................................................................6
Our project has three main modules........................................................................................6
1.4 BLOCK DIAGRAM.................................................................................................................................7
Figure1.5-Overall Block Diagram..............................................................................................7
PROCESS MEASUREMENT...............................................................................................9
CHAPTER 2.............................................................................................................................10
Temperature Measurement...................................................................................................10
2.1 BASIC CONCEPTS...................................................................................................................................10
2.1.1 Techniques of temperature measurement.................................................................................10
ii
2.1.2 Selected Sensor (Thermocouple) [6] [8]..........................................................................................13
2.2 DESIGN PHASE......................................................................................................................................14
2.2.1 Noise Filtration and Signal conditioning [7] [10].............................................................................14
2.3 IMPLEMENTATION..................................................................................................................................15
2.4 RESULTS...............................................................................................................................................17
2.4.1 Constraints................................................................................................................................17
CHAPTER 3.............................................................................................................................18
Current Measurement...........................................................................................................18
3.1 BASIC CONCEPTS...................................................................................................................................18
Over current protection....................................................................................................18
Performance monitoring...................................................................................................18
Power consumption..........................................................................................................18
3.1.1 Techniques of current measurement.........................................................................................19
Invasive techniques...........................................................................................................19
Conclusion..........................................................................................................................21
Non-Invasive technique....................................................................................................21
3.1.2 Selected technique.....................................................................................................................22
Hall Effect Sensor................................................................................................................................22
3.1.3 Comparison................................................................................................................................25
3.2 DESIGN PHASE......................................................................................................................................25
3.2.1 Design Approach........................................................................................................................26
3.2.2 System Definition.......................................................................................................................27
3.2.3 Location of Current Meter.........................................................................................................28
3.2.4 Block Diagram for Current Display.............................................................................................29
3.2.5 Block Diagram for Current Data Communication......................................................................29
3.2.6 Alarm System.............................................................................................................................30
3.3 IMPLEMENTATION..................................................................................................................................31
3.3.1 Simulation..................................................................................................................................31
3.3.2 LT Spice Design..........................................................................................................................31
3.3.3 Testing Hall’s Sensor..................................................................................................................32
3.3.4 PCB Designing............................................................................................................................32
iii
3.3.5 Proteus Design...........................................................................................................................33
3.3.6 PCB Layout.................................................................................................................................33
3.3.7 PCB............................................................................................................................................33
3.4 TESTING & RESULTS...............................................................................................................................34
3.4.1 Results.......................................................................................................................................34
3.4.2Difficulties in Measurement........................................................................................................39
3.5 ALTERNATIVE APPROACH FOR DEMONSTRATION..........................................................................................39
3.5.1 Proteus Design...........................................................................................................................40
3.5.2 PCB Layout.................................................................................................................................40
3.5.3 PCB............................................................................................................................................40
3.6 CONSTRAINTS........................................................................................................................................40
Chapter 6...............................................................................................................................42
Future Plans...........................................................................................................................42
REFERENCES...........................................................................................................................43
REFERENCES RELATED TO BOOKS:...................................................................................................................43
REFERENCES RELATED TO INTERNET SOURCES:..................................................................................................43
iv
Tables of Figures
Figure 1.1-Electroplating Industry Setup.......................................................................2
Figure1.2-View of an Electroplating System...................................................................3
Figure 1.3-Inside view of Electrolytic Tank..................................................................................................5
Figure 1.4-Heating system of the tank...........................................................................................................5
Figure1.5-Overall Block Diagram..................................................................................7
Figure 2.1-Physical appearance.....................................................................................................................10
Figure 2.2-Structure of Thermocouple........................................................................................................11
Figure 2.3-RTD physical appearance...........................................................................................................11
Figure 2.4- Bridge Configurations for Use of RTD.................................................................................11
Figure 2.5-Thermistor appearance................................................................................................................12
Figure 2.6-LM 35 IC package............................................................................................................................13
Figure 2.7-Flow Diagram of Temperature....................................................................14
Figure 2.8- Internal Structure of AD 595......................................................................14
Figure 2.9- Input Signal Filtering................................................................................15
Figure 2.10-Temperature measurement Circuit Schematic............................................16
v
Figure 2.11-Pcb Layout for Temperature measurement................................................16
Figure3.1: Resistive Shunt.........................................................................................20
Figure3.2: Current Transformer..................................................................................21
Figure3.3: Columbia tong test ammeter.....................................................................................................22
Figure3.4: Fiber-Optic Current Sensor........................................................................................................24
Figure3.5: Hall Sensor........................................................................................................................................25
Figure3.6: Hall's Effect Principle................................................................................25
Figure3.7: Ratiometric Hall Effect Sensor....................................................................26
Figure3.8: Closed loop current sensor construction....................................................27
Figure3.9: Design Procedure.....................................................................................29
Figure3.10: Location of Current Meter........................................................................31
Figure3.11: Magnified view of location where current assembly has to be installed.............31
Figure 3.12: Block Diagram for Current Display...........................................................32
Figure 3.13: Block Diagram of Current Data Communication........................................32
Figure 3.14: Alarm system.........................................................................................33
Figure3.15: Schematic Design for current measurement..............................................34
Figure3.16: After signal conditioning..........................................................................................................35
Figure3.17: Hall's output voltage...................................................................................................................35
Figure3.18: Output voltage of hall sensor.................................................................................................35
Figure3.19: Input voltage to hall sensor.....................................................................................................35
Figure3.20: Pin configuration of hall sensor............................................................................................35
Figure3.21: PCB design for current measurement.......................................................36
Figure3.22: PCB for current measurement..................................................................36
vi
Figure3.23: Schematic for variable power supply........................................................43
Figure3.24: PCB layout of variable power supply.........................................................43
Figure3.25: Final look of variable power supply PCB...................................................44
Tables of Tables
Table 1: Results of Temperature measurement.........................................................................................17
Table 2: Comparison of techniques.................................................................................................................28
Table3: Readings with small intervals of current......................................................................................37
Table4: Readings with magnetic field in reverse direction....................................................................37
Table 5: Readings of apparatus #1..................................................................................................................38
Table 6: Readings of apparatus #2..................................................................................................................38
Table 7: Readings of apparatus #5..................................................................................................................38
Table8: Scaled reading of apparatus #2........................................................................................................39
Table9: Average taken of above three tables...............................................................................................39
Table10: Readings with calculated magnetic field
Table11: Magnetic field values for full range of current
vii
Abstract
In electroplating industry, there are huge tanks containing highly corrosive liquids.
Materials to be electroplated are submerged in tubs. For good electroplating the supplied
voltage has to be provided continuously for the specified time. This process requires very
high DC current up to 2000 Amperes. Gas burners are used for heating the liquid.
Burners are placed inside the tubs and it is required to maintain the temperature within a
specified range (55°C – 65°C). The objective is to display the current and temperature
values on Liquid Crystal Display (LCD) continually for each tank. Data storage device is
to be used for storing measured values after specified intervals. Current and temperature
display is required to ensure the better monitoring of the system. An alarm circuitry has
to be developed to ensure safety limits for currents. In addition to display and alarm
circuitry, a temperature control circuitry has to be integrated to maintain the temperature
within the limit. Another important module is the long distance communication of stored
data through GSM.
1
CHAPTER 1
INTRODUCTION
2
1.1 Introduction
Electrochemical industry demands high rating and complex operating parameters. Measurement
of DC current and temperature is required for the better industrial performance. In electroplating
process the highly corrosive chemicals are used for the electrolysis process, thus making the
environment acerbic and corrosive. Better insulation is required for the apparatus in such
circumstances. The apparatus is insulated with the internal rubber lining in most industries. [1]
Among the several techniques of metal finishing, electroplating is one of the most widely used in
industries. Let’s have a look on the some working parameters of the electroplating industry. [1]
1.1.1 Electroplating Industry
Electroplating is a technique of deposition of' a fine layer of one metal on another by a process of
electrolysis. It imparts various properties and attributes to the finished product, such as corrosion
protection, enhanced surface hardness, luster, color and aesthetics.
Figure 1.1-Electroplating Industry Setup
Plating process is mainly for the manufacture of simple and cheap parts. The basic electroplating
system consists of
A plating bath which is either acid bath or alkaline bath.
An anode (positive electrode) and a cathode (negative electrode).
3
An Electrolytic solution which is usually water containing metallic salts. A small
amount of acid/ alkali is added to improve its conductivity and reactivity.[1]
Figure1.2-View of an Electroplating System
Usually, the bath is a metallic container, lined with acid/alkali resistant membrane.
The electrochemical process requires a fixed voltage source as a driving force. The electrodes are
dipped in the electrolytic solution and voltage is applied across them. The metal salts
subsequently dissociate into anions and cat-ions, which then deposit onto the items to be plated.
There is the flow of direct electric current across the bath solution causing the migration of
Positively charged particles (anions) towards the negative electrode (cathode)
Negatively charged particles (cat-ions) towards the positive electrodes (anode)
It’s an exothermic process thus leading the elevated bath temperature as compared to the ambient
temperature. The process efficiency depends to some degree on the
Concentration of acid and alkali in the solution
Temperature
Voltage applied across the electrodes
4
An electroplating apparatus consists of a complex set of equipment, including motors, tanks,
water rinses, filters, heaters, electrical power supplies, process monitoring devices, process
control devices, and they have to be maintained and check on regular basis to get the desired
results. There are several parameters that have to be processed during the electrochemical
process. These parameters are as follows:
Solution temperature
Current at each electrochemical step
Cell voltages
Solution level
Solution chemistry
(Metal concentration, pH, Specific gravity, Additive concentration)
Impurity levels
Among all the above mentioned parameters, we are focusing on the measurement of the three
basic parameters .i.e. current, voltage and temperature. [1] [4]
Solution temperature is the most effective parameter of the electrolysis cell. There is a constant
stirring with help of a stirrer within the tank to keep the temperature equally distributed.
Next parameter under consideration is the high DC current which is flowing outside the cell
through cables or bars which is directly related to the deposition rate. At start high current flows
due the rapid movement of the charges, with the passage of time the charges start accumulating
on the plates thus the potential difference decreases, decreasing the flow rate of charges. So it is
important to display and store its value so that when there is an electrical short or open between
the anode and cathode, contamination or polarization of the anode, or any change in the solution
it could be noticed.
1.1.2 System under our consideration
In our case electrolysis is being carried out in an internally rubber-lined tank. The electrolyte is
highly corrosive. It is operating by a 24 volts supply. A DC current of 600-2000A is flowing
through the external circuit. The temperature range that has been appropriate for the process is
5
within 55oC to 65oC. Some images will help us get a better understanding of our system
operation
1.2Objective
Our objective is to make a generalized kit capable of measuring temperature, voltage and current.
It is required to display the measured data 24 hours a day along with it develop an alarm circuitry
to initiate a buzzer in case of open and short circuit. Yet another objective is to develop an
automatic control for burner in order to maintain the temperature limit within 55oC to 65oC. To
add flavor to our project data storage and communication module has been made an objective of
our project.
1.3 Scope
Our project has three main modules
Measurement
Control
Communication
Figure 1.3-Inside view of Electrolytic Tank Figure 1.4-Heating system of the tank
6
The hitherto bench mark of our project is that it has many features yet an easy and cheap solution
for an electrochemical industry. Our project has wide ranging scope as every electro- winning
industry has same control parameters and has a requirement of measuring current, temperature
and voltage to reduce maintenance cost and to ensure safety and better performance. Our
designed kit is optimized, simple, easy, economical, integrated and advanced solution; thus
fulfilling the demands of automation and electro-winning industries. It can also find its
application in laser and welding workshops.
1.4 BLOCK DIAGRAM
Figure1.5-Overall Block Diagram
Current, voltage and temperatureis sensed bya sensing circuitry. Output signals from the
respective sensors are then conditioned separately. The signals after amplification and noise
7
rejection are sent to controller. Controller outputs the message to alarm circuitry to initiate a
buzzer whenever safety limits are exceeded. Controller must be intelligent enough to process the
values, display them on LCD and then to store them in computer using serial port interfacing and
then communicate them to the respective channel through GSM communication. Controller also
controls the solution temperature. Temperature control is in the closed loop with the controller
and the electrochemical plant. When the solution temperature exceeds the safety range; a
feedback is send to controller which in turn sends the message to the mechanical control of
burner to turn-off or turn-on the burner accordingly.
8
PROCESS MEASUREMENT
9
CHAPTER 2
Temperature Measurement
2.1 Basic Concepts
Temperature is one of the parameters that need to be measured and observed in almost every
industry. You can measure temperature in many different ways that vary in equipment cost and
accuracy. The most common types of sensors are thermocouples, RTDs, and thermistors. For
simple calibration of these devices we can also use make use of these normal mercury
thermometers.
There are several things to consider when choosing a sensor to monitor temperature or any other
parameter. The important items are accuracy, reliability, sensor life, cost, signal conditioning,
and maintenance.It is also important to keep in mind that the electrolyte to be used is highly
corrosive. And we are required to place the sensor in the solution for the accurate temperature
measurement. It is recommended that not to place sensors on the tub as it will include an error of
an ambient environment temperature.
2.1.1 Techniques of temperature measurement
Let’s have a bird’s view at various available options for temperature measurement. At the end we
will make the best choice according to our requirements and available resources.
Thermocouple[6][9]
The basic working principle of this temperature sensor is
based on “See beck effect” which says that when two
wires of dissimilar metals are joined together at both ends
Figure 2.1-Physical appearance
10
make a loop that produce a potential difference proportional to the potential difference between
the junction.
Since Thermocouple is a differential device so the temperature of one of these junctions should
be known for single temperature measurement. The known end is known as the Reference or
cold junction and the measuring end is known as measurement or hot junction.
It is low in cost and is widely used in
industrial application. Moreover, it doesn’t
require any external excitation signal for its
operation. It gives an analog output in the
form of a voltage signal in millivolts scale
that needs to be amplified and converted to a
digital output for further use. So we will require
some signal conditioning as well.
The thermocouples are further classified into different types based on the metals joined together
in its construction, their temperature ranges and theirs sensitivity to the change in temperature.
These types include J type, K type, E type, T type and few more. K-type thermocouples are
easily available in the market, composed of chromel and alumel (Nickel-chromium and Nickel-
aluminum) whose range extends between -200 C and 1200C. It has a sensitivity of about
41µv/C with an accuracy of about 1-2C.
Resistance Temperature Detector (RTD)
Platinum RTD is a device made of coils or films of metal
(usually platinum). It works on the fact that when heated,
the resistance of the metal increases; when cooled, the
resistance decreases. Passing current through an RTD
generates a voltage across the RTD. By measuring this
voltage, you can determine its resistance and, thus, its temperature. The relationship between
Figure 2.2-Structure of Thermocouple
Figure 2.3-RTD physical appearance
11
resistance and temperature is relatively linear. Typically, RTDs have a resistance of 100 Ω at 0
°C and can measure temperatures up to 850 °C.
Figure 2.4-Bridge Configurations for Use of RTD
Thermistor
Thermistor is basically a resistance whose resistance
varies significantly with the temperature. They are
very much similar to RTD’s but differ in the material
used as thermistors use ceramic or polymers but RTD
always use metals. However, unlike RTDs,
thermistors have a higher resistance (2,000 to 10,000 Ω)
and a much higher sensitivity (~200 Ω/°C), allowing
them to achieve higher sensitivity within a limited
temperature range (up to 300 °C).
It is also used in bridge configuration. Its response is highly non-linear. They are not really
suitable to be used in rough or harsh environments as they are physically sensitive too and can
get damaged if proper care is not done in installing them. It is also highly susceptible to self-
heating errors.
Figure 2.5-Thermistor appearance
12
LM 35
Lm 35 is a precision integrated circuit temperature sensor having a highly
linear behavior operating in the range of 50C-150C. It works as a surface
mounted IC device which means that it has to be in direct contact to the
thing whose temperature is to be measured. It requires a signal of 5V for its
operation yielding an output of 10mV/C. The self-heating errors are very
likely to appear if not given proper attention.
Corrosion Resistance
As we are dealing with an electroplating system which means that our environment is highly
corrosive. So we need to protect our sensor from getting corrode otherwise we will have to
replace it after regular intervals to ensure proper monitoring and control which could be very
irritating as well as cost ineffective.
There are various materials or metals that are corrosion resistant like glass, plastic (PVC),
Teflon, platinum etc. The choice of material depends upon the cost and utilization.
2.1.2 Selected Sensor (Thermocouple) [6] [8]
From our above discussion and literature review, K-type Thermocouple appears to be our best
choice. Following reasons can be attributed to this opinion:
No external excitation required
Good linearity over short temperature range
Appropriate temperature range and sensitivity value
2.2 Design Phase
We will explore our selected option in a bit more detail. The block diagram will represent our
working process in a better way:
Figure 2.6-LM 35 IC package
13
Figure 2.7-Flow Diagram of Temperature
2.2.1 Noise Filtration and Signal conditioning [7] [10]
We are using a K-type thermocouple which gives the output in the form of few mV. AD 595 is
used for the signal conditioning of our signal. AD 595 provides gain of almost 247.3 to the input
signal of about less than 5mV (for our desired range) to convert it into a change of 10mV/ C
which can be analyzed far more easily. It also provides us with thermal junction compensation.
The internal architecture of this IC is shown below:
Figure 2.8-Internal Structure of AD 595
This signal can be distorted by noise so we use an RC filter to eliminate the noise before sending
the signal to AD 595. The values of resistor and capacitor are chosen to be 1kΩ and 1µF
respectively to obtain a low pass filter of 160Hz (approx.). We hope to eliminate the distortion
14
form the signal and we are not sending the output signal over large distances, so we decided that
it will serve our purpose well enough.
Figure 2.9-Input Signal Filtering
So we the help of these simple circuits we will be able to achieve a signal which will form the
input of our controller. The built-in ADC of our controller allows us to give the analog input
directly to it which will carry out the further processing.
2.3 Implementation
We implemented the designed circuit to measure the temperature of boiling water.
Thermocouple was inserted into the water filled container (care was taken that it does not come
into contact with the walls of the container as it may affect the calibration). The IC (AD595) was
powered by 5V supply. Pins 4, 7 and 13 were grounded along with the pin no. 14. A low pass RC
filter is applied to the input before processing it through AD595. The schematic is drawn
using“Altium” software. The Schematic is:
15
Figure 2.10-Temperature measurement Circuit Schematic
This schematic was first tested on the breadboard and the readings were recorded in the table.
The initially tested circuitry was then implemented on the PCB and incorporated in the whole
system. The PCB layout is shown below:
Figure 2.11-Pcb Layout for Temperature measurement
16
2.4 Results
Temperatur
e
Output voltage
1st reading 2nd reading 3rd reading 4th reading
50 0.49 0.50 0.50 0.49
51 0.50 0.52 0.51 0.50
52 0.51 0.53 0.52 0.51
53 0.52 0.54 0.54 0.52
54 0.53 0.55 0.55 0.53
55 0.54 0.57 0.56 0.54
56 0.55 0.58 0.57 0.55
57 0.56 0.59 0.58 0.57
58 0.57 0.60 0.59 0.58
59 0.59 0.61 0.60 0.59
60 0.60 0.62 0.61 0.60
61 0.61 0.63 0.63 0.61
62 0.62 0.64 0.64 0.63
63 0.63 0.66 0.64 0.64
64 0.64 0.67 0.65 0.66
65 0.65 0.68 0.66 0.67
Table 1: Results of Temperature measurement
2.4.1 Constraints
All the experiments are carried out in the laboratory or clean environment
The effect of the corrosive solution or hazardous environment is not as much as present
in the actual industrial environment.
17
The current system is very small as compared to the industrial setup, so only a single
thermocouple is used at present.
18
CHAPTER 3
Current Measurement
3.1 Basic Concepts
Every electro – winning, industry is characterized by the high dc current rating. Electric current
is an important physical quantity and its measurement is required in many applications such as in
industrial, automotive or household fields.High Current measurement in the industry is very
important as it provides following
Over current protection
Prevents equipment failure
Helps ensure safety
Performance monitoring
Improves output handling
Reduce waste
Power consumption
Monitoring of current draw can help in improving efficiency of overall system
Can be useful in trend analysis of the system.
Electric current sensing is done by using various techniques. Different technical solutions to
measure currents can be found in literature. Below is an overview of important measurement
techniques and their respective advantages and disadvantages have been shown.
3.1.1 Techniques of current measurement
1. Invasive
19
2. Non-Invasive
Invasive techniques
A technique in which the circuit path is broken down to measure the current is known as invasive
technique
Resistive Shunt
Current transformer
Resistive Shunt
A shunt resistor is used to measure electric current either alternating or direct. In this technique,
current is measured by measuring the voltage drop across the resistor. A shunt is an element that
is used in a circuit to redirect current. The current is divided over the shunt and the ammeter,
such that only a small (known) percentage flows through the ammeter. [14]
Figure3.3: Resistive Shunt
PROS
Cheap, Simple and Easy
Size
Can be accurate
CONS
Insertion loss.
High-Side current measurement is difficult.
20
Shunt resistor requires careful design
It exhibits temperature non-linearity
Requires additional amplifiers and high impedance buffers.
Current Transformer
A current transformer is a device that is designed to produce an alternating current in its
secondary winding which is proportional to the current being measured in its primary
side.It reduces high voltage currents to a much lower value and provides a way of monitoring the
actual electrical current flowing in an AC transmission line using a standard ammeter.Due to this
type of arrangement, the current transformer is often referred to as a “series transformer”. [15]
Figure3.4: Current Transformer
PROS
No offset voltage
No external power required
CONS
Large Size
Expensive
Only measure AC.
Conclusion
21
Invasive techniques are not an effective way of measuring current. The major reason is that it is
not possible in the industrial environment, to remove the insulation and break the current path
just for the sake of current measurement and then tie up everything after the lengthy procedure.
It also has practical constraints of industrial and automation industry as the readings obtain by
this process is not stable.
Non-Invasive technique
Columbia tong test ammeter
Fiber-optic current sensor (FOCS)
Hall Effect Sensor
Columbia tong test ammeter
The Columbia tong test ammeter can measure both AC and DC
currents and provides a true RMS current measurement of non-
sinusoidal or distorted AC waveforms.
The iron jaws of the meter direct the magnetic field surrounding
the conductor to an iron vane that is attached to the needle of the
meter.
The iron vane moves in proportion to the strength of the magnetic
field, and thus produces a meter indication proportional to the
current. [16]
PROS
Portable
Cost effective
CONS
The scale shows unstable readings
Show non-linear trend and is unsuitable for measuring low currents.
Figure5.3: Columbia tong test ammeter
22
Fiber-Optic Current Sensor
It is an advanced technology, which is a quite better option
for the electrical industrial environment. It has wide
applications in electro-winning, industry because there are
heavy, large current buses, and thus it’s difficult and complex
to measure the current rating. These types of current sensors
are made up of single - ended optical fibers. These fibers
surround the current carrying conductor and utilize the
Faraday Effect (magneto- optic effect) to measure the current.
PROS
Simple and Easy interfacing
Cost effective
CONS
Insertion loss (loss in signal power due to reflected and dielectric losses)
Its manufacturing and handling requires a specialized workforce and advance techniques.
3.1.2 Selected technique
Hall Effect based current transducers [5]
Hall Effect Sensor
Figure3.7: Hall Sensor
Figure3.6: Fiber-Optic Current Sensor
23
Principle
When a current carrying conductor is placed inside the magnetic field, the conductor experiences
some force known as Lorentz force. Due to this force, the charge distribution get disturbed thus
giving rise to the hall voltage. This hall voltage is proportional to the current flowing through the
conductor. [3]
Figure3.8: Hall's Effect Principle
Description
The hall element is placed inside the magnetic field, as the current flows through the wire the
voltage is generated proportional to it. The Hall element voltage signals are then fed to high gain
amplifiers. The signal conditioning is done before sending the signal to the Arduino board. The
most widely current sensing technique used in the electro-winning, industry is sensing current on
the Hall Effect based transducers. It is widely used in current clampers.
Figure3.9: Ratiometric Hall Effect Sensor
PROS
No insertion loss
Total electrical insulation of the measuring device
24
Ability to measure a wide current range
CONS
Large size
Expensive
Applications
Industrial equipment
Industrial controls
Electrical systems
Commercial/industrial HVAC
Types
Hall Effect Switch Sensor
Hall Effect Latch Sensor
Ratiometric, Linear Hall-Effect Sensor
Ratio metric, Linear Hall-Effect Sensor
Ratiometric linear sensors are small, versatile sensors. The Ratiometric output voltage is set by
the supply voltage and varies in proportion to the strength of the magnetic field. It is due to the
Hall effect-integrated circuit chip that provides increased temperature stability and sensitivity.
The Ratiometric linear sensors respond to either positive or negative magnetic field (Gauss). It
provides a robust design over a wide temperature range. [13]
Figure3.10: closed loop current sensor construction
25
3.1.3 Comparison
Current sensing method
Shunt resistor Hall Effect Current sensing transformer
Accuracy Good Good MediumAccuracy vs. Temperature
Good
Poor
Good
Cost Low High MediumIsolation No Yes Yes
High Current - Measuring Capability
Poor
Good
Good
DC Offset Problem Yes No No
Saturation | Hysteresis Problem
No
Yes
Yes
Power Consumption High Low Low
Instructive Measurement
Yes
No
No
AC|DC Measurements
Both
Both
Only AC
Table 2: Comparison of techniques
3.2 Design Phase
Design phase significantly includes the system definition and design approach. The design
approach is a chart representing the approach used for selecting input and output interfaces. The
system definition determines the sensor specifications. Sensor specifications are analyzed to
determine the required sensing device package, as well as the functional characteristics and
specifications for the input and output interfaces. Electrical characteristics must be considered in
the design phase.
Sensing modifications
600A –DC current
Develop input interface
Develop output interface
Breadboard sensor
Measure Gauss vs. distance
Analyze data
26
3.2.1 Design Approach
Figure3.11: Design Procedure
To Measure DC Current of the range 1000 A
Sensing Device Input Requirements
UGN3120Hall
Input voltage range: 4.5 – 6 VInput voltage Change: ±1VTemperature Range: 125oCMagnetic flux:Safety Factors: No Current pass through Hall Sensor.System Tolerances: Series Circuit so, same current follow through entire circuit.Environmental Condition: Suitable for Corrosive Enviorment.
Sensing Device Output Requirements
Output: Voltage proportional to the Current.Amplifier: To increase voltage from mill volts to volts.Scaling: Scaling the voltage between 0-5 V.DC Null: DC Null removal by variable resistor and op-amp.Offset: Introduce offset to keep the system to one battery.
System Characteristics & Constraints
Complete Sensing Device Specifications
Location of Meter:At the top right corner of the tank.Available Power Supplies: 9V battery.Repeatability: 50 trillion times Response Time: 3µ sec
27
3.2.2 System Definition
28
3.2.3 Location of Current Meter
Figure3.12: Location of Current Meter
This current measuring device has to be designed for the industrial environment, so
before designing any assembly, the environmental conditions and space where assembly
has to be fixed should be considered. The above snap (Fig 11 & Fig 12) has been taken in
the industry, showing the space has been shown where current measuring device has to
Current meter
Figure3.13: magnified view of location where current assembly has to be installed
Current carrying bar
Fixed end
29
be installed. There are the bars from which current flows. A rectangular shaped magnet
will surround the bar. The measuring device will be installed at the fixed end.
3.2.4 Block Diagram for Current Display
The block diagram below shows the process by which signal is obtained and processed.
This signal conditioned signal is then given to the Arduino board so that it can display on
the LCD. Input pins in Arduino board takethe analog signal of maximum 5V, thus the
hall’s voltage should be scaled between 0-5V. This analog signal is then digitized by
using ADC (Analog to Digital Converter). [8]
Figure 3.12: Block Diagram for Current Display
3.2.5 Block Diagram for Current Data Communication
For current data beingsent as a text message; services of GSM have been used. Analog
data after digitizing is stored and is then communicated by using GSM. Through GSM,
data has to be sent to the cellular network.
Current Sensing Circuit Voltage (mV) Amplifier
Ardiuno Board (Analog input
pin)
Inbuilt ADC (Analog to Digital
Converter)
Output on the LCD Display
30
Figure 3.13: Block Diagram of Current Data Communication
3.2.6 Alarm System
Figure 3.14: Alarm system
3.3 Implementation
Implementation includes
Current Sensing Circuit Voltage (mV) Amplifier
Ardiuno Board (Analog input pin)
Inbuilt ADC (Analog to Digital
Converter)
RX & TD pins of GSM (SIM 900-RS232 MODEM)
Through cellular network to Base
Station
31
1) Simulation 2) PCB Designing
3.3.1 Simulation
Simulations have been done in the LT Spice. Hall sensor is not available in the LT Spice,
so Hall’s voltage is approximated by a voltage source. The Hall’s output changes 2.3 m V
per 1 Tesla change in magnetic flux (Hall’s book). The voltage is then signal
conditioned.
Signal conditioning includes amplification and filtering for the smooth output. This
voltage is known as offset voltage. The offset removal circuitry is added to remove the
offset. This offset is inherent in ratiometric hall sensor. The output drops towards 0V or
rises towards 5V, according to magnetic polarity, at a rate of 2.5mV / Tesla.
The design has been given below:
3.3.2 LT Spice Design
Figure3.15: Schematic Design for current measurement
32
Hall’s output voltage After signal conditioning
3.3.3 Testing Hall’s Sensor
Ratiometric hall sensor is not easily available in the market; so it has been purchased
online.Hall’s book states that “If there is no magnetic field applied the sensor outputs
approximately half of the supply voltage” (hall’s book)
3.3.4 PCB
Designing
PCB is designed in Proteus. The available hall sensor’s packages present in the Proteus
do not have the same pin configuration as SS490 series (purchased hall sensor’s series).
Hall sensor is estimated with a transistor having the same pin configuration as a
purchased hall sensor.
Figure3.16: hall's output voltage Figure3.17: after signal conditioning
Figure3.18: input voltage to hall sensor Figure 3.19: output voltage of hall sensor
33
3.3.5 Proteus Design
Figure3.20: PCB design for current measurement
3.3.6 PCB Layout
Figure3.2114: PCB layout for current measurement circuit
3.3.7 PCB
Figure3.22: PCB for current measurement
3.4 Testing & Results
The PCB testing has been done in welding Lab. The experiments have been done on DC
inverter welding machines.
Hall sensor
34
3.4.1 Results
These readings are obtained after experimentation.
Current (A) Voltage (V)
0 2.56
55 3.3
92 3.37
108 3.45
133 4.00
163 4.30
Table3: readings with small intervals of current
It is found that voltage doesn’t change much at small intervals. It detects at least 50 A of
change in current. Another trend was observed during experimentation that if current was
increased hall’s voltage start decreasing; the reason for this trend is that the magnetic
field is in a clockwise direction this time.
Table4: Readings with magnetic field in reverse direction
The presence of a south-polarity (+B) magnetic field, perpendicular to the branded
face of the device package, increases the output voltage, VOUT, in proportion to the
magnetic field applied, from VOUTQ toward the VCC rail. Conversely, the application
of a north polarity (–B) magnetic field, in the same orientation, proportionally
Current (A) Voltage (V)
0 2.56
50 3.5
100 3.01
150 2.7
35
decreases the output voltage from its quiescent value. This proportionality is specified
as the magnetic sensitivity of the device and is defined as
Sens=Vout ( – B )−Vout (+B)
2 B
In USA, the only maximum available DC current is up to 165A. So experimentation was
done by measuring the voltage for the change of 50 A. Experimentation was done by
using different welding machines. As hall’s output voltage also depends on the diameter
of the current carrying wire; thus experimentation was done by changing wire as well.
[11]
Apparatus #1 Apparatus #2
Apparatus #3
Offset voltage (voltage at 0A) = 2.56 V
Then scaling all values to the same level
(amendments are made in Apparatus #2 only)
Table 5: Readings of apparatus #1 Table 6: Readings of apparatus #2
Table 7: Readings of apparatus #5
Current (A) Voltage (V)
0 2.60
50 3.65
100 4.06
150 4.11
Current (A) Voltage (V)
0 2.56
50 3.5
100 3.7
150 4.2
Current (A) Voltage (V)
0 2.56
50 3.5-3.6 (3.55)
100 3.94
150 4.06
36
Current (A) Voltage (V) Scaling (Voltage - 0.04)
0 2.56 2.56
50 3.65 3.61
100 4.06 4.02
150 4.11 4.07
Table8: scaled reading of apparatus #2
After taking an average of the readings listed in apparatus#1, apparatus #2 and apparatus
#3, the trend was found to be
Current (A) Voltage (V)
0 2.56
50 3.55
100 3.89
150 4.11
Table9: average taken of above three tables
From the graph of Output Voltage vs. Gauss following calculations has been done
The graph has been attached at the end.
By extrapolation the values of magnetic field are found to be
m = y2− y1x2−x1
Here m = slope of the graph
x1= arbitrary chosen voltage at which value of gauss is known
x2 = voltage at which value of gauss is unknown
y1= gauss value corresponding to known voltage x1
37
y2= unknown value of gauss
Let’s take y2= 200; y1=0; x2= 3; x1=2.5
We get
m = 400
Now to find the first value
m = 400; y2=? ; y1= 400; x2= 0.99; x1=3.5
We get
y2 = -604
Now to find the second value
m = 400; y2=? ; y1= 400; x2= 1.33; x1=3.5
We get
y2 = -468
Now to find the third value
m = 400; y2=? ; y1= 600; x2= 1.55; x1=4.0
We get
y2 = -380
Now if offset is removed we get
Current (A) Voltage (V) Voltages without
offset (V)
Magnetic Field
(Gauss)
0 2.56 0 -
38
50 3.55 0.99 -604
100 3.89 1.33 -468
150 4.11 1.55 -380
Table10: readings with calculated magnetic field
The literature of hall sensors claims that hall sensor can give 5 V at maximum at its
output without including offset; thus from it the maximum value of current that hall
sensor is capable of measuring can be determined. [12]
After extrapolation we obtain
The maximum DC current that “selected” hall sensor can measure is roughly nears to
2250 A.
Current (A) Voltages without
offset (V)
Magnetic Field
(Gauss)
0 0 -
50 0.99 -604
100 1.33 -468
150 1.55 -380
300 2.21 -116
450 2.43 -28
600 2.65 60
750 2.87 148
900 3.09 236
1050 3.31 324
1200 3.53 412
1350 3.75 500
1500 3.97 588
1650 4.19 676
1800 4.41 764
1950 4.63 852
39
2100 4.85 940
2250 5.07 -
Table11: magnetic field values for full range of current
3.4.2Difficulties in Measurement
Below are listed some constraints which hinder the progress of the project a lot.
In USA, the maximum DC current source available is in welding workshop.
The company for which the project has to be made is in Lahore, so it’s not
possible to visit that company on a weekly or even on a monthly basis.
The maximum rating of DC current source is 160 A and hall sensor can detect
the current changes of at least 50 A, so maximum three readings can be taken.
Current only flows through the wire if welding is in process.
Three persons are required to measure the current (a welder, a helper and a
person to measure voltage with DMM)
3.5 Alternative Approach for Demonstration
After successful testing of current measurement circuitry, an alternative approach for
demonstration was developed as whole integrated assembly cannot be shifted to welding
workshop.
A variable voltage source of 0-5V was made for demonstration purpose. This voltage
source will be an approximation of the hall sensor’s output voltage. This analog signal
will be provided to the Arduino board for display and storage.
40
3.5.1 Proteus Design
Figure3.23: Schematic for variable power supply
3.5.2 PCB Layout
Figure3.24: PCB layout of variable power supply
3.5.3 PCB
Figure3.25: Final look of variable power supply PCB
3.6 Constraints
In USA, the maximum DC current source available is in welding workshop.
41
For the temperature measurement, we need a burner; which is not possible to
bring in the welding shop.
It is neither possible nor allowed to take the whole setup to the welding
workshop for experimental reasons.
Even there is no space to install all the setup there for experimental purpose.
It is not allowed to work in the welding workshop without the supervision of
the staff (most of the time staff is busy in their own work).
Current only flows through the wire if welding is in process.
The company for which the project has to be made is in Lahore, so it’s not
possible to visit that company on a weekly or even on a monthly basis
The power supply is required for the Arduino and GSM module to power up.
Due to these constraints the project is an approximated model of the setup which has to
be installed in the industry.
42
Chapter 6
Future PlansThis project will fulfil the tasks it aimed to accomplish by the bench inspection. Almost every aspect is done. All that is left is to install everything in real industrial environment. The result is of very good quality for a student who has no prior experience in measuring and controlling basic industrial parameters. Some of the future plans have been listed below
To make an assembly to hold the setup in the welding lab, without the help of
helpers.
To make a small setup of portable power supplies, so that the whole setup can be
shifted to the welding shop.
To use electric ways of heating water (use of an electric heater)
To find some suitable location with heavy DC current, other than welding shop
(Laser Dept in PINSTECH)
Too often visit the industry in Lahore, and to check the prepared setup there.
43
REFERENCES
References Related to Books:[1] J. M. Mauskar, Comprehensive Industry Document on Electroplating industry, India, 2007.
[3] Jim Lepkowski, Motor Control Sensor Feedback Circuits, Microchip Technology Inc, USA, 2003.
[4] Tom Ritzdorf , Modern Electroplating, 5th edition, Yorktown Heights, NY
[5] Brady Haran, Hall Effect Sensing and Application, USA, Honeywell Inc, 2003.
[7] Joe Marcin, Thermocouple Signal Conditioning Using the AD594/AD595,U.S.A.
[6] Matthew Duff and Joseph Towey, Two Ways to Measure Temperature Using Thermocouples Feature Simplicity, Accuracy, and Flexibility, U.S.A,2010.
[10] Bob LeFort and Bob Ries, Taking the Uncertainty Out of Thermocouple Temperature Measurement, (with the AD594/AD595), Norwood, Massachusetts.
[8] Analog Devices, Practical Design Techniques For Sensor Signal Conditioning-Analog devices technical Reference Books.: Prentice-Hall, USA, 1999
[11] Lewis Loflin, Using Ratiometric Hall Effect Sensors, USA, 2013
[13] Edward Ramsden, Hall-Effect Sensors: Theory and Application, Newness. Copyright, 2011
[14] Joshua Myers, Ryan Laderach, Stephen England, Kenji Aono, Current Sensing Using Resistive Shunts, USA, 2011
[15] Steve Laslo, Current Transformers, USA, March, 2012.
References Related to Internet Sources:[2] URL: http://www.edaboard.com/thread25183.html
[9]Thermometrics, 18714 Parthenia St Northridge, CA 91324.
URL: http://www.thermometricscorp.com
[12] Robtillaart, Code A1301/A1302 Hall Effect Sensor, 2013.
URL: http://playground.arduino.cc/Code/HallEffect
44
[16] Columbia AC/DC Clamp-On Tong Test Ammeters
URL: http://www.weschler.com/_upload/sitepdfs/ammeters/clampons.pdf