DAQ data acquisition and logging system using 8051

Data Acquisition (DAQ) technology provides the link between the data-generating sensors and data-storing recording devices. DAQ can also provide the means for driving external actuators from a computer, by the generation of external excitation signals. DAQ technology includes both hardware and software. 

Thanks to the recent advancements in processor technology, the low cost personal computer is now the most important carrier for data acquisition cards. The high clock speeds of modern central processing units (CPUs), such as Pentium and PowerPC, enables higher sampling rates. This along with high performance bus architectures such as PCI, cheap RAM, and fast voluminous hard disks make long-term continuous measurements possible.

Traditionally, the clock speed of the computer CPU can significantly affect the performance of the DAQ system. However, newer direct memory access (DMA) transfer technology speeds up the system by using dedicated hardware to transfer data directly into system memory. Thus, the CPU is not burdened with moving data and is therefore free to engage in more complex processing tasks. In addition, if an application requires real-time processing of high-frequency signals, a dedicated digital signal processing (DSP) chip can be built-in on the DAQ board to share the work load of the main processor.

Another important development is portable data acquisition based on laptop computers with PCMCIA cards. This configuration allows more convenient field measurements that used to be troublesome for practicing engineers.

Emerging broadband internet and broadband cellular phones outperform traditional modem hookups using RS-232 or RS-485 serial communication ports. These emerging communication technologies will make remote monitoring and access measurements more achievable.

In short, the current level of data acquisition technology, although still not perfect, is far more effective and efficient than a decade ago. In the future, one can expect even more affordable and accurate measurement instruments, some that could be fitted into computers as small as modern hand-held calculators or personal digital assistants.

The source code for the project is written in Visual Basic and C-language. You can download the vb-code , c-code, schematic, and if you don't have a cross compiler then you can directly burn the HEX file on to your chip

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RVDT( Rotary variable differential Transformer)

The Rotational Variable Differential Transformer (RVDT) is used to measure rotational angles and operates under the same principles as the LVDT sensor. Whereas the LVDT uses a cylindrical iron core, the RVDT uses a rotary ferromagnetic core. A schematic is shown below.

Typical RVDT Sensor Top of Page Common Specifications Common specifications for commercially available RVDT's are listed below: Input: Power input is a 3 to 15 V (rms) sine wave with a frequency between 60 to 20,000 Hz.

 Angle: Capable of continuous rotational measurement. However, most RVDTs have effective angle limits of up to ±60°. Nonlinearity: Higher accuracy in the smaller angle range: 0.25% @ ±30°, 0.50% @ ±40°, 1.50% @ ±60°. 

 Pros and Cons

 • Pros: - Relative low cost due to its popularity. - Solid and robust, capable of working in a wide variety of environments. - No friction resistance, since the iron core does not contact the transformer coils, resulting in an very long service life. - High signal to noise ratio and low output impedance. - Negligible hysteresis. - Infinitesimal theoretical resolution. In reality, angle resolution is limited by the resolution of the amplifiers and voltage meters used to process the output signal. - No permanent damage to the RVDT if measurements exceed the designed range.

 • Cons: - The core must be in contact (directly or indirectly) with the measured surface which is not always possible or desirable.

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Working Of Spool valve with best Video

Spool Valve : A valve that controls the direction of hydraulic fluid flow. A spool valve consists of cylindrical spools that alternately block and open channels in the hydraulic system. 

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4 Common Mistakes In Instrumentation And How To Avoid Them

4 Mistakes and how to Avoid them .pdf

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PLC DCS SCADA & HMI for Beginners

 PLC DCS SCADA & HMI for Beginners

Let's see how simple we can make it - by first building a SCADA system - and then by building a DCS system - each from the ground up.

Suppose that we're building a brand new factory - and suppose that our first piece of equipment is something like a big industrial oven. This thing will be made up of heaters, and valves, and conveyor motors, and other assorted machinery - so let's say we get to work and we build us an oven. Now that we've got the mechanical part of the oven built - we need some type of controller for it - something to accurately control all of those different parts in order to turn raw material into a sellable final product. So what type of control are we going to use? How about a PLC - a Programmable Logic Controller?

In very simple language a PLC is a type of computer. But the computers that most people are familiar with use a keyboard as an input device and a screen for an output device. PLC's don't have a keyboard. So for an input device, we use an "input module" which is basically a little box with a row of screws on the front of it. We wire up a bunch of pushbuttons, sensors, switches, etc. to the little screws ... and this will serve as the input device for our PLC "computer". We do something similar for an output device. Instead of using a screen for an output device, we use an "output module" which is basically another little box with a row of screws on the front of it. We wire up a bunch of solenoid valves, indicator lamps, motor starters, etc. to the little screws ... and this will serve as the output device for our PLC "computer".

So for this first example, let's say that we decide to go with a PLC system. We buy the PLC and install it by connecting wires between the oven and the PLC. Then we buy a copy of the programming software from the PLC manufacturer - and then we write a program for the PLC - we'll probably use "ladder logic" programming, since that's what most PLC's use as their native language. And now the PLC is just about ready to properly control the system - except that we still need some way for the operator to set and to monitor the temperatures - and to start and stop the conveyors and so forth.

Now for this small system, some meters and pushbuttons and some thumbwheel switches might do just fine. We could wire those up and build us an operator's control panel for our oven. But another (better?) way would be to use an HMI - a Human Machine Interface. (This used to be called an MMI - Man Machine Interface - but now-a-days we've got to be more politically correct.) So we buy us a nice desktop computer and some type of HMI software. We'll need to program the HMI - and usually this is done by dragging and dropping pictures of meters and knobs and buttons onto our computer screen. In other words, we build a "virtual" control panel for our operator to use. We link these on-screen controls to the PLC's memory through a communication cable. And now we're finally ready to go. Great so far - and we start making some money with our factory.

Later on, business is good and we decide that our factory could use two additional ovens. So we get the mechanical parts built - and now we need to decide how we're going to control these new ovens. Now the original PLC that we used for oven number one is quite capable of controlling the two additional ovens. We just might need to add a few additional I/O modules to the chassis - and we'll certainly need to run some more wires - but basically the same old PLC "brain" has plenty of extra horsepower to handle the new ovens. But - here's an idea: Suppose that we buy two new PLC's - one for each new oven. Now that's certainly going to cost us more money, but at least this way each oven could operate - or be shut down - completely separately from the other two systems. That's going to make scheduling maintenance a lot simpler - and generally give us a lot more flexibility in all of our operations. Plus - by having three controllers - we're not putting "all of our eggs in one basket" as the old saying goes.

We talk the boss into it - and we buy the new PLC's and install them - and download copies of the original program into them - and we're just about ready to go. But how about that operator control piece of the puzzle? Since we're already using an HMI for our operator's control panel, all we have to do is make two copies of the screens from our original oven - and set these new copies up on the operator's HMI computer. Finally, we extend the communication cable from the HMI station over to the two new PLC's - and now we're up and running.

Next the boss hires a bean-counter - someone whose job involves maximizing our factory's profits. Now this person requires data - he needs to know how much it costs to operate the ovens - and how much product we run through them - and how much of that product is "off-spec" and wasted. The best way to get all of this production data is to ask the PLC's - after all, they're the "brains" that are controlling the system. So let's upgrade the old HMI that the operator has been using - to something with more features. This will be called a SCADA system - for "Supervisory Control And Data Acquisition". It will still have control screens with all of the virtual buttons and meters and other whatnots that the operator needs to control the ovens - but it will also have some additional features beyond the HMI - features which will allow the SCADA system to suck the production data right out of the PLC's - and to store that data in some type of computer database. Later, the bean-counter can retrieve that production data and analyze it to his little heart's content. All is well.

Quick review so far: The machinery in our factory is being controlled by PLC's. For a little while we used an HMI (Human/Machine Interface) software package - so that the Human operator could Interface (that is, monitor and operate) the Machine. Later we moved from the HMI up to a more powerful software package - a SCADA (Supervisory Control And Data Acquisition) system. This new software still allowed our human operator to Supervise and Control the system - and it also added some features for Data Acquisition for the bean-counter's benefit.

Now let's start over with a new factory - and this time we'll use a DCS (Distributed Control System).

Suppose that this time we know in advance that the factory we're about to build is going to involve a rather sophisticated process - one which is going to require many interrelated steps - all of which must be carefully coordinated in order to produce a sellable final product. We're talking about chemicals - or pharmaceuticals - or something along those lines. (The term "continuous process" is a familiar buzzword for something like this.)

Now yes, we COULD use PLC's for this type of factory - and yes, we COULD use a SCADA system to supervise and control the whole thing. But - many engineers would decide to go with a DCS for something like this. And that's what we're going to do.

Now suppose that our new factory still needs something along the lines of our previous ovens - how would we control these? Instead of putting a PLC on each oven - we'll use a separate DCS "controller" for each oven. Now at first glance, these controllers will each look a lot like an individual "I/O module" or "I/O card" in a PLC system. They usually slide right into a chassis - and have wires for inputs and outputs connected to the front of them. So most DCS systems tend to look a lot like a PLC system. The big difference is that each of these DCS "controller/card" devices will be individually programmed. That's where the term "DISTRIBUTED" comes from - the control (or "brain-power" if you prefer) is DISTRIBUTED among many individual controllers. Specifically, in a typical PLC system we generally have only one "brain" (or processor) in each chassis - and then several I/O (input/output) modules in the chassis to handle the signal wires to-and-from the machinery. On the other hand, in a typical DCS system we'll have several "brains" (or controllers) in a chassis - and the I/O wiring associated with each particular "brain's" machinery will be connected directly to the front of that individual controller.

Now what about the operator control function? Well, one integral part of a DCS system is a large computer (usually a quite powerful one) which looks a lot like a SCADA terminal. And it does exactly the same job. First, it gives the operator a series of control screens with all of the virtual buttons and meters and other whatnots that he (or she) requires in order to control the machinery. Second, it also has the features required to suck the production data right out of the individual controllers - and to store that data in some type of computer database. And in most DCS systems, there is a third function of the DCS terminal: The programming software for the individual controllers is also usually available on this terminal - so that reprogramming the controllers is possible right over the existing data communication cables.

Quick review of the DCS approach: The machinery in our factory is being controlled by many individual little controllers. Our operator uses a DCS terminal (computer) to monitor and operate the machinery. This DCS terminal also has features to acquire production data and store it in a database for later analysis. Additionally, the DCS terminal usually has the programming software required for the individual controllers available. And all of the hardware and all of the software required for our DCS system is generally provided by just one manufacturer. Some people think that's a good thing - and other people think that's a bad thing.

So which is the better approach - PLC or DCS? This is usually decided by the engineers who initially design the factory. And in practice, there are a lot of factories out there who use combinations of the two approaches.

Finally: Please remember that this was intended to be a general "beginner level" discussion - there are exceptions to all of these "rules" ... but hopefully this will give you a "starting point" from which to build.

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Level Measurement level sensor and level Transmitter

This post is the starting of a series of post which will give you detailed explanation about level measurement, its types, principles, etc. I have divided this section into a number of post so that it becomes easy for readers to understand and follow. To see all the post published related to level measurement i.e to view the whole topic in a single page click the label titled ' LEVEL'

Introduction:

Measurement of liquid level is important in a variety of industrial processes. The liquid level may be expressed in terms of the pressure column exerts over a datum level or in terms of the length of the liquid column.

Liquid level may be measured by two methods:

1. Direct method
2. Indirect method

In direct methods the hydrostatic pressure of the liquid column is measured.

Indirect methods of liquid level measurements generally used in industries are:

1. Hydrostatic pressure type
2. Electrical methods.

Hydrostatic pressure type:

A liquid in a tank at rest exerts a force on the wall of the tank. This force in a liquid at rest is known as hydrostatic pressure. This is proportional to the depth (or height) of liquid in the tank. 

Hydrostatic pressure methods used for liquid level measurement are listed below:

1. Pressure gauge method
2. Air Bellows
3. Air Purge System (or) bubbler system
4. Liquid purge system
5. Diaphragm box type
6. Force balance type


Electrical Methods:

In electrical methods, liquid levels are converted into electrical signals and it can be measured by electrical or electronic means.

The types of electrical methods are:

1. Resistive (or) contact point type
2. Inductive method.
3. Capacitive method


The upcoming posts will cover the above mentioned types and methods in detail.

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PLC Simulation with software and Examples

PLC Simulation with software and Examples

Programmable Logic Controller Simulation Kit

What is the PSIM PLC Simulator.?

PSIM is actually three distinct programs combined into a single package. First, PSIM contains a PLC Ladder Logic editor that allows users to create and edit PLC programs using Allen Bradley PLC-2 family instructions. Secondly, PSIM emulates the scanning sequence of a PLC. When placed into the "RUN" mode, the users program is scanned and the appropriate I/O is updated just as would occur in an actual PLC. Thirdly, PSIM contains a number of animated simulations which respond accurately to the inputs, and outputs of the emulated PLC. A conveyor based filling line, Traffic intersection and Batch mixing simulations present life-like challenges for the student programmer.

Why this PLC Simulator is now available Free.?
PSIM was developed in 1993 when training for Allen Bradley PLC2 and PLC3 processors was at its peak. At the same time computers were showing up everywhere in Educational and Training facilities. What was needed, was a software based PLC training package that would run on these new computers and reduce if not eliminate the need for $25K-$50K PLC training stations. Also, if the software could also simulate some real-time industrial processes, so much the better. We developed PSIM to do just that! Since 1993, thousands of students in both schools and industry have used PSIM in their PLC programming courses and we now feel that PSIM has more than paid for itself. Even though PSIM is DOS based and emulates an older generation of PLCs, it still remains an excellent tool for introducing students to the fundamentals of PLC programming. As a programmer I'm pleased to make a few extra dollars, but as a teacher, I am even more pleased to see students enthusiastically hone their talents with a tool of my making. I am intent on not letting dollars dull this enthusiasm.

SOFTWARE SPECIFICATIONS:
Industrial Applications Software (Simulations):
The PSIM software includes the following simulated processes:
(1) Automated filling system

• Operator Station Panel and controls
• Conveyor with position sensors (photo switch)
• Hopper with motorized chute control
• Product Level Sensor
• Conveyor Motor
• Visual PLC Data Table Display including timers and counters

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(2) Batch Mixing system Simulation

• Operator Control Panel
• 2 filler pumps and piping
• 2 flow meters on filler lines
• 1 mixing motor
• 1 high level sensor
• 1 low level sensor
• 1 gas fired heater (controlled valve)
• 1 temperature sensor
• 1 discharge pump
• 1 discharge flow meter
• 1 Visual PLC Data Table display including timers and counters

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(3) Intersection Traffic Light Control Simulation

• 2-way traffic lights system
• 2 Green Lights
• 2 Red Lights
• 2 Amber Lights
• Visual PLC Data Table Display including timers and counters
• 2 way traffic flow

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(4) Hardware Input and Output Simulator

• 4 toggle switches (SPST)
• 2 momentary normally open switches
• 2 momentary normally closed switches
• 8 controllable lights
• Visual PLC Data Table Display including timers and counters

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PLC Emulator Software
The PSIM software includes a full-featured built-in PLC Emulator package that runs concurrently on the same computer with the Industrial applications software (simulations) described above. With a single keystroke, the user may toggle back and forth between the display of the animated process simulation and the Ladder Rung Program Editor of the emulated PLC.
The Program Editor is both user friendly and full-featured. Students may add, delete and modify program-rungs, branches and instructions using simple menu selections.
To test the new or modified ladder program, a single keystroke toggles the student back to the Process Simulation screen and places the PLC in the 'Run' mode. The process simulation will then react accurately to the student's newly programmed rungs which are constantly being scanned in the background by the PLC run-time emulator.
By incorporating the Editor and run-time scanning of a PLC into software capable of running and interacting with the industrial process simulations, PSIM provides a single computer hi-tech solution to Programmable controller student training, whether running on the network of a computer Lab, or on the users own laptop computer. The PSIM system allows a simple low-cost solution to PLC training while attaining superior student concept retention.

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Minimum Hardware Requirements

• Most Computers capable of running "DOSBox" software
• 640 KB RAM
• EGA color display 

Download link

Download Plcsimulator

Download Link 2 

LogixPro v1.6.1_PLC Simulator_proffesional.rar

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Stock market free tips 100%

 Hello evryone ,
i have recently started trading in the stock market and have become highly successful in the stockmarkets here are some of the stocks you need to watch out for.
1) Voltas
2) Shree Renuka Sugars
3) Essar Oil
4) Network 18
All of these are midcaps and will give you good returns....
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