Digital Data Acquisition System

In general analog DASs are used for measurement systems with wide bandwidth. But the accuracy is less. So digital DASs which have high accuracy, low per-channel cost and narrow bandwidth (slowly varying signal) are designed. Figure  shows the block diagram of a digital data acquisition system. The function of the digital data acquisition system include handling analog signals, making the measurement, converting and handling digital data, internal programming and control.

Block diagram of a digital data-acquisition system

Here, the transducer translates physical parameters to electrical signals acceptable by the acquisition system. The physical parameters include temperature, pressure, acceleration, weight, displacement, velocity etc. Electrical quantities such as voltage, stance, and frequency may be measured directly. The signal conditioner includes the supporting circuitry for the transducer. This circuit may provide excitation power, balancing circuits and calibration elements and an example of this is a strain-gauge bridge lance and power supply unit The scanner or multiplexer accepts multiple analog inputs and sequentially connects them to one measuring instrument. The signal converter translates the analog signal to a form acceptable by the analog to digital converter like an amp1ifier used for amplifying low-level voltages generated by thermocoup1es or strain gauges.
 
   The analog to digital converter (ADC) converts the analog voltage to its equivalent digital form. The output of the ADC may displayed visually and is also available as voltage outputs indiscrete steps for further processing or recording on a digital recorder. The auxiliary section contains instruments for system programming and digital data processing such as linearizing and limit comparison. These functions may be performed by individual instruments or by a digital computer. The digital recorder records digital information on punched cards, perforated paper tape, magnetic tape, typewritten pages or a combination of these systems. Digital recorder may be preceded by a coupling unit that translates the digital information to the proper form for entry into particular digital recorder selected.


Interfacing of transducers

Interfacing is defined as the interconnection of different 3 to perform a function in a compatible and co-ordinated fashion. Since, both analog and digital instruments are often used in measurement systems, interfacing is needed under the f categories.

1. Interfacing analog to analog instruments

2. Interfacing analog to digital instruments

3. Interfacing digital instruments to other digital device like printer, computer etc.,

SIGNAL CONDITIONING CIRCUITS: Data acquisition systems

A typical data acquisition system consists of individual sensors with the necessary signal conditioning, data conversion, data processing, multiplexing, data handling and associated transmission, storage and display systems.

Data acquisition systems are used to measure and record signals obtained in two ways. They are



    i) Signals originating from direct measurement of electrical quantities (DC and AC voltage, frequency etc.,)

    ii) Signals originating from transducers (Strain gauges, thermocouple etc.,)

    Generally, the instrumentation systems can be classified into analog systems and digital system Analog systems deal with measurement information in analog form. An signal may be defined as a continuous function, such as a plot of voltage versus time, or displacement versus pressure. A digital quantity may consist of a number of discrete and discontinuous pulses whose time relationship contains information about the magnitude or the nature of the quantity.

Block diagram of an analog data acquisition system

It consists of tranducers, signal conditioners multiplexer and output devices such as display, recorder and magnetic tape. Transducers are used for translating physical parameters into electrical signals. The Output of the transducer is to signal conditioning circuit where the signal is amplified and modified to the required level. The analog multiplexer selects of the several input signals (transducer signal) and the output he multiplexer is given to a display device or a recorder or a magnetic tape.

The characteristics of the Data Acquisition System (DAS) depend on both the properties of the analog data and the processing carried out. Based on the environment, the DAS is classified into types as those suitable for favourable environments (minimum interference and electromagnetic induction) and those intended for hostile environments.

•   The DASs are designed based on the following factors.

1. Accuracy and resolution

2. Number of channels to be monitored

3. Analog or digital signal

4. Single channel or multichannel

5. Sampling rate per channel

6. Signal conditioning require of each channel

7. Cost

• Objectives of a DAS

1. It must acquire the necessary data at correct speed and at the correct time.

2. It must use all the datas efficiently to inform the operator about the state of the plant.

3. It must monitor the complete plant operation to maintain on-line optimum and safe operations

4. It must provide an effective human communication system and be able to identify problem areas,
    thereby minimising unit availability and maximising unit through point at minimum cost.

5. It must be able to collect summaries and store data for diagnosis of operation and record purpose

6. It must be able to compute unit performance indices using on-line, real-time data.

7. It must be flexible and capable of being expanded for future Requirements.

8. It n be reliable and not have a down time greater than 0.1%.

SIGNAL CONDITIONING CIRCUITS: Differential amplifiers

Electronic measurement systems are combinations of instruments and components interconnected to perform an overall measurement function. The system components must not only perform their individual functions properly 6ut must also work effectively with the other components making up the system. This requirement points out the importance of ensuring that proper interfacing exists between all components making up the system. Generally in a measurement system, the input variable is in the analog form that has to be converted to digital form for the purpose processing, transmission, display and storage. All these functions performed by the data acquisition system as well as the different types of power and loss measurements.


Differential amplifiers

Phase of Electricity

Single phase AC circuit:

• Two wires connected to electricity source
• Direction of current changes many times per second

3-phases of an electric system

Three phase systems:

• 3 lines with electricity from 3 circuits
• One neutral line
• 3 waveforms offset in time: 50-60 cycles/second

 A single-phase AC circuit has two wires connected to the source of electricity. However, unlike the DC circuit in which the direction of the electric current does not change, the direction of the current changes many times per second in the AC circuit depending upon the frequency of the supply. The 240 volt (V) electricity supplied to our homes is single-phase AC electricity and has two wires: 'active' and 'neutral'.

Three lines carry electricity from three electrical circuits, and they share a common neutral line (i.e. three active lines and one common neutral line). Three-phase systems have 3 waveforms (usually carrying power) that are 2/3 π radians (120 degrees,1/3 of a cycle) offset in time.

The figure shows one cycle of a three-phase system, from 0 to 360 degrees (2 π radians), along the time axis.

The plotted line represents the variation of instantaneous voltage (or current) in time. This cycle will repeat 50 or 60 times per second depending on the power system frequency. The colors of the lines represent the American color code for three-phase systems: black=VL1 red=VL2 blue=VL3.

Star connection

Delta connection

The three-phase supply system is further represented by star and delta connection as shown in the figure. But as part of this training we will not explain these in detail.

Generation & Distribution Of Electricity

Electricity is mostly generated by power stations that use fossil fuels (coal, gas, oil) and nuclear facilities that use uranium. Due to environmental and safety concerns, and more recently energy security concerns as the oil supply is dependent on fewer and fewer countries, alternative sources of energy are being explored.
Renewable energy provides 21 percent of the world energy needs, including hydropower (20 percent), solar, wind, geothermal, biomass, and tidal energy (approximately 1 percent but growing). As the renewable energy sector grows, the technologies used are become more efficient and less expensive. Therefore prices are becoming more comparative to electricity from non-renewable sources.

• Electricity generation: fossil fuels and uranium 

• Renewable energy is growing

                           This figure illustrates the generation, transmission and distribution of electricity

• AC generators (“alternators”) generate electricity
  
  1.  Electricity generated at 9-13 KV
  2.  Power generated from 67.5 to 1000 MW
   
• Power stations: generating transformers (GTs) to increase voltage to 132-400 KV

• Substations: step-down transformers to reduce voltage before distribution

• Electricity is mostly generated by AC generators called “alternators” in thermal, hydro or nuclear power plants at 50 or 60 cycles per second. 

• Electricity is typically generated at about 9 to 13 KV at the generator terminal. The power generated by one generator (also termed as UNIT) is in the range of 67.5 MW, 110 MW, 220 MW, and 500 MW, although 1000 MW generators also exist.

• Higher MW rating of generation capacity is preferred because of less auxiliary power consumption and other operation & maintenance cost. 

• Electricity must be generated when it is needed since electricity cannot be stored. All power stations have generating transformers (GTs) that increase the voltage to extra high voltages (EHV, e.g. 132 KV, 220 KV, 400 KV) prior to transmission. 

• Similarly, sub-stations have step-down transformers, which reduce the voltage for distribution to industrial, commercial and residential users through distribution lines. 

• There is no difference between a transmission line and a distribution line except for the voltage level and power handling capability. Transmission lines operate at EHV and are usually capable of transmitting large quantities of electric energy over great distances. Distribution lines carry limited quantities of power at a lower voltage over shorter distances.

Benefits of high voltage transmission

• Less voltage drop: good voltage regulation 

• Less power loss: high transmission efficiency 

• Smaller conductor: lower costs  

Less voltage drop: Voltage drops in transmission/distribution lines are dependent on the resistance, reactance and length of the line, and the current drawn. For the same quantity of power handled, a higher voltage results in a lower current drawn and lower voltage drop. Benefit is good voltage regulation i.e. the difference between voltages sent and received at small.

Less power loss: the power loss in lines is proportional to the resistance (R) and the square of the current (I), i.e. PLoss = I2R. A higher voltage results in lower currents and therefore lowers power losses. Benefit is high transmission efficiency
Smaller conductor: a higher voltage results in lower currents and therefore a smaller conductor is needed to handle the current. Benefit is less capital and erection cost.

Intelligent Ambulance with Automatic Traffic Control

INTRODUCTION


In todays world health hazards are a major concern. Especially people in the older age group are the victims, and moreover the traffic conditions are worsening day by day, which results in traffic jams.

Many important jobs get delayed due to these trafic jams.Ambulance service is one of the major services which gets affected by traffic jams. To solve this problem we have come up with the solution of “Intelligent ambulance with automatic traffic control”.

Here we are tracking the patient’s health conditions. The health parameters such as Heart rate, body temperature, Blood pressure and Blood level are sent to the hospital using the on board GSM unit. All these parameters are displayed in the hospital unit on a pc with the help of visual basic s/w.

Simultaneously if at all the Ambulance encounters the taffic jam in the route, the driver is provided with the remote to control the traffic signals.The particular signal is made Green for some time and after the ambulance passes by,it again regains its original flow of sequence of signaling.


LITERATURE SURVEY

Previous work on home vital signs monitors can be seen in the current models that are in hospitals and homes. There are many different types and brands of vital signs monitors available today. They range in size, function, and price. Most are very expensive, costing patients or healthcare providers upwards of $2,500 per system.

There are many different types of vital signs monitors, so many patents of vital signs monitors exist. One such patent is a blood pressure and heart rate monitoring method and apparatus by Hewitt . This system uses an auscultatory transducer and a microprocessor-based circuit to record blood pressure and heart rate. It also uses a new method to measure blood pressure without unnecessary constriction of the patient’s limb.

So far in the market only the devices measuring different parameters are available,which are all stationary,but we are putting efforts to send this information wirelessly over the long distance using GSM unit.


 LOGICAL BLOCK DIAGRAM

Explanation of Logical Block Diagram

As we can observe there is a chowk shown in the diagram, consisting of four different lanes. An ambulance is going from lane1. The patient is carried in the cardiac van,whose various parameters are being measured by the sensory units inside the van. These parameters are constantly being sent to the hospital unit via GSM transreciever,in the form of a message of data (SMS).

The hospital you can see is at the side of road and it is receiving these SMS’s via a dedicated mobile phone. The information is shown on the pc connected to this mobile phone via data cable.The s/w used here is a very user friendly and front end s/w, i.e Visual basics.

At the same time, ambulance is also making the lane 1’s signal green and all other signals as red,due to traffic. This is achieved by RF link via TX 433 and RX 433 pair.Microcontroller timers and counters are used for controlling

Logical block diagram provides logic behind the project and gives complete overview of project. It shows logical flow behind the project. In this all 3 units that is Ambulance , Hospital and Traffic sigal units are shown .Here the driver selects the lane number, and then the particular signal is made Green.

So logical block diagram is all about logical flow of the project.

PROJECT:- HIGH EFFICIENCY SOLAR PANEL WITH SOLAR PATH TRACER

ABSTRACT

Solar energy systems and solar panels are one of the most popularly used energy systems now.
The importance of the same must be raised to a very high value in future years.
In our project we realize a new solar energy system with very high efficiency than ordinary ones. Our solar system consists of a solar path tracer.
The maximum electrical energy produces in solar cells when they are in perpendicular with the sun beams or the panel in parallel with the sun.
But in ordinary solar panel this is possible only for very few hours (3 or 3.5). In our system the panel must be in parallel with the sun with the help of a solar path tracer system.
The panel moves with the sun through out the day time. So the beams are always perpendicular with the solar cells.
As a result the whole system is about 45 % more efficient than normal type.This is a microprocessor based system with LDRs and stepper motor. The panel resets to its starting position at night time.

BLOCK DIAGRAM

CIRCUIT DIAGRAM

PROJECT:- PC BASED WIRELESS ELECTRICITY METER BILLING SYSTEM

ABSTRACT

The electricity office has send employees for taking meter reading every month, which is an expensive and time consuming job. This project provides a convenient and efficient method to avoid this problem. The electricity office can take the readings of consumers from their office computer.

                 This is an embedded tariff calculation project that has a LCD at the consumer side to display the bill amount hence the postage of bills to the consumer can be avoid. This is made possible by implementing RF wireless communication between the consumer side and office end. The officers have to type the consumer number and the reading will be provided in a flash. The power supply to defaulters who do not pay their bill on time can be cut off from the office side and once the bill is paid power can once again be restored.

                  Thus this project reduces the task of the electricity board by being able to take meter readings of the each of the consumers from the office itself and displaying the bill amount at the consumer end. It reduces a huge amount of labor work making this project really worth implementing.

BLOCK DIAGRAM

CIRCUIT DIAGRAM

 

PROJECT:- SUBSTATION GSM

ABSTRACT:

GSM (Global System for Mobile communications: originally from Group Special Mobile) is the most popular standard for mobile phones in the world. Its promoter, the GSM Association, estimates that 80% of the global mobile market uses the standard. GSM is used by over 3 billion people across more than 212 countries and territories. Its ubiquity makes international roaming very common between mobile phone operators, enabling subscribers to use their phones in many parts of the world. GSM differs from its predecessors in that both signaling and speech channels are digital.

Here we introduces a new system which is very much applicable in the field of electrical power transmission and thus in our day today life. The remote controlling of substation machines is possible with this system.

Load shedding is very much common in our state. The proper switching of electrical machines mainly transformers are possible with this system via SMS from the mobile phones of the operators.

The functions of distribution transformers for the corresponding areas are controlled by finger touch remotely in accurate manner. Proper timing and accurate functioning are the main advantages of this system.


WORKING PRINCIPLE:

Mobile phone and GSM modem are the main part of this project. The SMS from the mobile phone is detected by the GSM modem. There are unique SMS codes are assigned with the mobile phone for the control of different electrical machines (transformers).

These different codes are detected by the GSM modem and it communicates with the MCU either directly or through the computer.

The MCU received the digital data from the modem for particular operations, According to the stored program inside it. The information from the modem are as per the SMS from the mobile phone.

The machines are connected with the relays .the functions of these relays are controlled by the MCU through relay interfacing buffer circuits.

Thus the distribution transformers are controlled by the messages from the mobile phone of the operators.

MCU-micro controller unit

BLOCK DIAGRAM

CIRCUIT DIAGRAM

PROJECT:- SCR BASED DC DRIVE

ABSTRACT

SCR (silicon controlled rectifier) based DC motor control is very useful in industries because they offer a continuous speed variation of 0 to maximum. These drives are static and have good reliability. These drives work under the principle of phase angle control. By means we are varying the triggering angle from 0 to 180 degree in every half cycle of rectified 50HZ AC mains to get the speed variation. When triggering angle varies the applied average voltage to the motor also varies. The rpm of dc motors have direct relation between rpm and applied voltage.

       The triggering angle variation is achieved by a microcontroller whose operation is hardwired to get ac synchronization with the applied ac mains. The motor is controlled by the microcontroller circuit according to the speed desire which is set by a variable knob provided to the user. The microcontroller collects the input voltage set by the knob control and with the help of the synchronization signal from the ac mains provides triggering pulses in each half cycle. The triggering pulses are the applied to the gate of thyristors in the drive through a pulse transformer which is used for isolation.

   For our project we use the popular PIC microcontroller (PIC 16f 73) from MICROCHIP CORPORATION. The drives are created by 25A SCRS. For our project we use 1HP dc motor to control.

BLOCK DIAGRAM

CIRCUIT DIAGRAM

PROJECT: FINGER PRINT BASED VOTING MACHINE

ABSTRACT

    Here we describe a system to identify a person based on their finger print. The people able for voting store their finger print in the system EEPROM by the authorities. When any one tries to enter by putting their finger in the module, the system first scan the finger inserted and compare the finger prints stored in the system memory. If the finger print does not match with the new entry the voting will not be allowed. If it matches with any one of finger print pre stored the system allows entry.

  The system is built around the popular MICROCONTROLER PIC 16F 877A. The microcontroller does the all control operation to read, compare and to control the other circuits. The system has a key board and an LCD display to see the status of operation. Using the key board we can add new finger prints when required. The system gives indication through an audible and visual means for operation status and also alarm when the person is unauthorized. We use finger print module from SUN ROM technologies which in built scanner, processor and memory to store finger templates also

The polled votes are stored in EEPROM. This EEPROM data is accessed after polling completed for publishing the results.

BLOCK DIAGRAM

CIRCUIT DIAGRAM 

LM35 series precision integrated-circuit temperature sensors

The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in degree Kelvin.

LM35 Feature

• Calibrated directly in degree Celsius (Centigrade)
• Linear + 10.0 mV/degree C scale factor
• 0.5 degree C accuracy guarantee able (at +25 degree C)
• Rated for full -55 degree to +150 degree C range
• Suitable for remote applications
• Low cost due to wafer-level trimming
• Operates from 4 to 30 volts
• Less than 60 microA current drain
• Low self-heating, 0.08 degree C in still air
• Nonlinearity only + - 1/4 degree C typical
• Low impedance output, 0.1 W for 1 mA load

LM35 Testing

To test the temperature sensor connect the positive terminal of 5V dc supply to the VCC pin and ground the GND pin by connecting it to the negative terminal of 5V supply.

Connect the output terminal to a DMM bring solder gun close to the sensor and the output voltage on the DMM.

The output of LM35 linearly varies with the temperature that is 10mV per degree C . So for room temp ie 27 degree C , 270 mV will be observed on the DMM.

Thermistor 

A Thermistor is a type of resistor with resistance proportional to its temperature. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.

Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range.

Basic operation

Assuming, as a first-order approximation, that the relationship between resistance and temperature is linear, then:

Change in resistance R = k X change in Temperature

k = first - order temperature coefficient of resistance.

Thermistors can be classified into two types depending on the sign of k.

If k is positive, the resistance increases with increasing temperature, and the device is called a positive temperature coefficient (PTC) thermistor, or posistor. 

If k is negative, the resistance decreases with increasing temperature, and the device is called a negative temperature coefficient (NTC) thermistor.

Resistors that are not thermistors are designed to have a k as close to zero as possible, so that their resistance remains nearly constant over a wide temperature range.

Short Notes on: Accuracy,Linearity,Precision,Threshold,Drift &Stability.

(i) Accuracy:

It is the degree of closeness with which the reading approaches the true value of the quantity to be measured.

(ii) Linearity:

The linearity is defined as the ability to reproduce the input characteristics symmetrically & linearly. The curve shows the actual calibration curve & idealized straight line.

(iv) Threshold:

If the instrument input is increased very gradually from zero there will be some minimum value below which no output change can be detected. This minimum value defines the threshold of the instrument.

(v) zero drift:

If the whole calibration gradually shifts due to slippage, permanent set, or due to undue warming up of electronic tube circuits, zero drift sets in. 

b) span drift or sensitivity drift
If there is proportional change in the indication all along the upward scale, the drifts is called span drift or sensitivity drift.

c) Zonal drift:

In case the drift occurs only a portion of span of an instrument, it is called zonal drift.

(vi) Stability:

It is the ability of an instrument to retain its performance throughout is
specified operating life.

Questions and Answers In Measurement & Instrumentation (part-2)

11)    List out the Various Static Characteristics.


         Accuracy, Precision, Sensitivity, Linearity, Reproducibility, Repeatability,
     Resolution, Threshold



12)    Define Error.

                Error is define as Difference Between Standard value and Measured Value
 Normally It is Mentioned In %
% Error = Absolute Error / Standard Value X 100 

13)    How the Measurement Data’s are evaluated?

          By using  statistical evaluation methods data’s are evaluated .
          the measured date  are evaluated by two method

       (i) Using Standard Formula

       (ii) Comparing Previous Results

14)    What is the importance of standard?

         All the instruments are calibrated at the time of manufacturer against measurement standards. A standard of measurement is a physical representation of a unit of
Measurement. A standard means known accurate measure of physical quantity.

15)    List out the Classification of standard.

            Primary standard,  Secondary standard, International standards

16)    What is the Difference between Accuracy & Precision?

                   It is the degree of closeness with which the reading approaches the true value of the quantity to be measured. The accuracy can be expressed in following ways: Point accuracy, Accuracy as percentage of scale span, Accuracy as percentage of true value,

17)    Define Resolution.

         If the input is slowly increased from some arbitrary input value, it will again be found that output does not change at all until a certain increment is exceeded. This increment is called resolution.

18)    What is Sensitivity?

                   The sensitivity denotes the smallest change in the measured variable to which the instrument responds. It is defined as the ratio of the changes in the output of an instrument to a change in the value of the quantity to be measured. Mathematically it is expressed as,

19)    Define Instrument Efficiency.

                    Instrument efficiency is defined as the ratio of measures quantity to the power taken by the instrument at full scale deflection.
                
20)    What is Calibration?

             Calibration is the process of making an adjustment or marking a scale so that the readings of an instrument agree with the accepted & the certified standard.

21)    How the Secondary standard Differ from the Sub Standard?

Secondary standard are Closer to true value, Protected in the national laboratory .

           Sub standard are almost closer to true value, It compared with the primary
            Standard, Consider as an accurate one.

22)     List out the Types of Error?

                The types of errors are follows
i) Gross errors
 ii) Systematic errors
iii) Random errors

23)    What are the Ways used for Minimizing the Error?

i) Selecting a proper instrument and planning and proper procedure for
        the measurement
ii) Applying the proper correction factors

iii) Calibrating the instrument carefully against a standard

24)    What is the use Swamping Resistance?

            To minimize the error , a swamping resistance made of manganin or constantan is connected in series with the coil .
25)    What are the Systems used to Measure the Data?

             i) Metric system
             ii) SI system