pressure on lcd screen free sample

Unbundled Channelization (Multiplexing) 5.7.1 To the extent NewPhone is purchasing DS1 or DS3 or STS-1 Dedicated Transport pursuant to this Agreement, Unbundled Channelization (UC) provides the optional multiplexing capability that will allow a DS1 (1.544 Mbps) or DS3 (44.736 Mbps) or STS-1 (51.84 Mbps) Network Elements to be multiplexed or channelized at a BellSouth central office. Channelization can be accomplished through the use of a multiplexer or a digital cross-connect system at the discretion of BellSouth. Once UC has been installed, NewPhone may request channel activation on a channelized facility and BellSouth shall connect the requested facilities via COCIs. The COCI must be compatible with the lower capacity facility and ordered with the lower capacity facility. This service is available as defined in NECA 4.

DS3 Loop DS3 Loop is a two-point digital transmission path which provides for simultaneous two-way transmission of serial, bipolar, return-to-zero isochronous digital electrical signals at a transmission rate of 44.736 megabits per second (Mbps) that is dedicated to the use of the ordering CLEC in its provisioning of local exchange and associated exchange access services. It may provide transport for twenty-eight (28) DS1 channels, each of which provides the digital equivalent of twenty-four (24) analog voice grade channels. The interface to unbundled dedicated DS3 transport is a metallic-based electrical interface.

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This article was co-authored by Linh Le and by wikiHow staff writer, Nicole Levine, MFA. Linh Le is a Certified Mobile Repair Specialist and the Owner of SC Mobile Repairs in San Clemente, California. With more than 12 years of experience, he specializes in smartphone, tablet, and smartwatch hardware repair. Linh has an iTech Mobile Device Repair Certification and an iOS Certification. He holds a Bachelor’s degree from The Franciscan University of Steubenville.

That annoying dead pixel on your TFT, OLED, or LCD screen might just be stuck and easy to fix. We"ll show you how to do it. You can still return your monitor if this doesn"t work; nothing we recommend here will void your warranty.

Yes, you should test any new monitor for bad pixels. You can simply run your screen through a palette of basic colors, as well as black and white in full-screen mode using a tool like EIZO Monitor Test.

EIZO Monitor Test is an online tool that lets you find and eventually fix stuck pixels. It packs many options into a single test window, but it"s easy to use once you have an overview.

To test your screen, check all the boxes you want to include in your test. We recommend the default setting of having all boxes checked. If you"re testing multiple monitors, you can open the test on an additional monitor. When you"re ready, click Start test to launch the full-screen test window.

Below you see the first test pattern. Each screen has an explainer in the bottom right detailing what you should look for. Next, you"ll see a menu that lets you go from one test to the next on the left. Move through the black and white screens and all the solid colors (green, blue, and red) and check our screen. To exit, press the ESC key or the exit symbol in the top right.

This is a very thorough test not only meant to identify bad pixels but also powerful enough to test the quality of your monitor. Unfortunately, with Flash no longer supported by most browsers, you"ll probably have to use the executable version to make it work.

Move the mouse to the top of the test window, and a menu will appear. There is an info window that you can turn off with a button in the top right corner of the menu. Then click on the Homogenuity test point and move through the three colors as well as black and white.

Fingers crossed, you won"t discover anything out of the ordinary. In the unfortunate case that you do, let"s see whether it"s a stuck or a dead pixel and what you can do about it.

A stuck pixel, sometimes wrongfully referred to as a hot pixel, is defective because it receives incomplete information. Hence, it appears in one of the colors that its three sub-pixels can form, i.e., red, green, or blue. Strictly speaking, hot pixels only appear in digital cameras when electrical charges leak into the camera"s sensor wells. Sometimes, stuck pixels fix themselves.

The tool will load a black browser window with a square of flashing pixels. Press the green button in the bottom right to go full-screen. Drag the flashing square to where you found the stuck pixel and leave it there for at least 10 minutes.

UDPixel, also known as UndeadPixel, is a Windows tool. It can help you identify and fix pixels using a single tool. The program requires the Microsoft .NET Framework. If you"re not on Windows or don"t want to install any software, scroll down for the online tools below.

Should you spot a suspicious pixel, switch to the Undead pixel side of things, create sufficient amounts of flash windows (one per stuck pixel), and hit Start. You can drag the tiny flashing windows to where you found odd pixels.

The PixelHealer lets you flash a combination of black, white, all basic colors, and a custom color in a draggable window with customizable size. You can even change the flashing interval and set a timer to close the app automatically.

Let it run through all colors in Auto mode to spot whether you have any weird pixels on your screen. If you do, start the fix, which will rapidly flash your entire screen with black, white, and basic color pixels.

Should none of these tools resolve your stuck or dead pixel issue, here is one last chance. You can combine any of the tools detailed above and the magic power of your own hands. There is a very good description of all available techniques on wikiHow. Another great step-by-step guide can be found on Instructables.

This works because, in a stuck pixel, the liquid in one or more of its sub-pixels has not spread equally. When your screen"s backlight turns on, different amounts of liquid pass through the pixel to create different colors. When you apply pressure, you"re forcing the liquid out, and when you release the pressure, chances are the liquid will push in, spreading around evenly as it should.

When all attempts to revive your bad pixel fail, the next best thing you can do is to make peace with it. One ugly pixel won"t break your screen, and eventually, you"ll forget about it. If the defect affects more than a single pixel, however, or just bothers you a lot, you can always replace your monitor.

First, check the warranty. The manufacturer or the marketplace where you purchased the monitor might cover dead pixels. Note that most manufacturers define a maximum number of allowable bad pixels for specific resolutions, and the warranty won"t apply until your monitor crosses that threshold.

Bright or dark sub-pixels can occur during the production of the LCD Monitor panel but does not affect the LCD Monitor functionality. The customer may notice the bright or dark spots if the film of the liquid crystal does not perform as expected while customers uses the LCD monitor. However, this is not considered a defect unless the number of bright and dark subpixels exceeds the maximum allowable threshold (...)

On a monitor with over 12 million pixels (Wide QXGA+, 2560x1600 pixels), for example, LG"s pixel policy says that 12 bright or dark sub-pixels is the maximum you have to tolerate.

Should all of these approaches fail to fix your dead pixel warrior, at least you"ll now know it"s not simple to fix, and, you might actually have to replace the screen.

Are you looking for how to get rid of those irritating spots on your phone screen? This article shows you everything you need to know on how to fix pressure spots on LCD screens and how to prevent them in the future.

One of the deadliest and most frustrating issues you could have with your mobile phone is screen damages. And for pressure spots on LCD screens, it"s somewhat annoying than breaking the whole screen itself, as it requires going for replacement in most cases.

As its name implies, pressure spots on phone screens can render the display useless (or irritating, based on how you see it) by creating spots of different shapes and styles on the screen. These spots show continually, and most times, permanently on the display and can obstruct your viewing or cause other problems such as dead pixels, flickering, or blurriness.

When you apply too much pressure on your phone’s display – whether accidentally, intentionally, or carelessly, it damaged the LCD components, hence creating different spots on the display.

Pressure spots on LCD screens can come in different forms and shapes depending on the density of pressure applied. Sometimes, the spots can be whitish, deep black, or come in various colors depending on what’s currently showing on the screen.

Unfortunately, learning how to fix pressure spots on LCD screens isn"t the same as learning how to fix simple hardware and software issues. Simply put, there is no way to repair a phone screen that was damaged by pressure.

Attempting to get rid of pressure spots on LCD screens can cause more harm than good. Hence, you had better find a professional phone repairer to help you with screen replacement.

Meanwhile, some users reported that the pressure spots on their phone screen got healed after a few years. But do you want to keep seeing the same issue on your screen for years? So, a screen replacement is the only way out.

Fortunately, if you use a TECNO, Infinix, or itel smartphone, Carlcare Service is the best bet for you when it comes to replacing your damaged screen and fixing other issues on the device. We"re the official after-sales service provider to render professional repair and customer services for these brands.

And if you’ve bought our extra Screen Protection Plan for your TECNO, Infinix, or itel device earlier, you might be able to replace your screen for free, or better still, get huge discounts on-screen replacement at Carlcare.

Also, if you notice pressure spots on your Syinix TV, the best thing to do is bring it down to our service centre for proper screen replacement with genuine stock parts.

Paying for screen replacement from your own pocket (especially when you don’t have any form of screen insurance or protection plan), can be a pain in the ass. However, there’s probably nothing you could have done better than learning how to protect your phone screen from pressure spots in the future.

Pressure spots on LCD screens (or any screen in general) occur accidentally or carelessly. The only way to avoid such damage in the future is to handle your phone carefully. Try as much to shun applying much pressure on the screen while playing games and performing other tasks.

When inserting your phone into your pocket, purse or bag, ensure there"s enough space to accommodate it. Also, ensure there are no other objects inside the pocket, purse, or bag.

Equally important, if you"re wearing a dress with tight pockets, we recommend you keep your phone somewhere else rather than forcing it inside the pocket, as it may be pressurized when you move your body.

Overall, the only way to prevent your phone screen from getting pressure spots in the feature is to handle it carefully whenever and wherever possible. If you ever come across the need to drop your phone somewhere, ensure you don’t place anything on it.

Taking these few things into consideration would help you protect your phone screen from pressure spots in the future, rather than looking for how to fix pressure spots on LCD screen when it happens.

Now, if you’ve accidentally applied much pressure on your phone’s screen and some spots are showing on it when you turn it on, the best thing you can do is to visit the official service provider for your device for a screen replacement. Trying to shift the spots away or performing some DIY tricks may cause more harm than good.

Touch panel technologies are a key theme in current digital devices, including smartphones, slate devices like the iPad, the screens on the backs of digital cameras, the Nintendo DS, and Windows 7 devices. The term touch panel encompasses various technologies for sensing the touch of a finger or stylus. In this session, we"ll look at basic touch panel sensing methods and introduce the characteristics and optimal applications of each.

Note: Below is the translation from the Japanese of the ITmedia article "How Can a Screen Sense Touch? A Basic Understanding of Touch Panels"published September 27, 2010. Copyright 2011 ITmedia Inc. All Rights Reserved.

A touch panel is a piece of equipment that lets users interact with a computer by touching the screen directly. Incorporating features into the monitor like sensors that detect touch actions makes it possible to issue instructions to a computer by having it sense the position of a finger or stylus. Essentially, it becomes a device fusing the two functions of display and input.

It"s perhaps not something we think of often, but touch panels have integrated themselves into every aspect of our lives. People who enjoy using digital devices like smartphones interact with touch panels all the time in everyday life—but so do others, at devices like bank ATMs, ticket vending machines in railway stations, electronic kiosks inside convenience stores, digital photo printers at mass merchandisers, library information terminals, photocopiers, and car navigation systems.

A major factor driving the spread of touch panels is the benefits they offer in the way of intuitive operation. Since they can be used for input through direct contact with icons and buttons, they"re easy to understand and easily used, even by people unaccustomed to using computers. Touch panels also contribute to miniaturization and simplification of devices by combining display and input into a single piece of equipment. Since touch panel buttons are software, not hardware, their interfaces are easily changed through software.

While a touch panel requires a wide range of characteristics, including display visibility above all, along with precision in position sensing, rapid response to input, durability, and installation costs, their characteristics differ greatly depending on the methods used to sense touch input. Some typical touch-panel sensing methods are discussed below.

As of 2010, resistive film represented the most widely used sensing method in the touch panel market. Touch panels based on this method are called pressure-sensitive or analog-resistive film touch panels. In addition to standalone LCD monitors, this technology is used in a wide range of small to mid-sized devices, including smartphones, mobile phones, PDAs, car navigation systems, and the Nintendo DS.

With this method, the position on screen contacted by a finger, stylus, or other object is detected using changes in pressure. The monitor features a simple internal structure: a glass screen and a film screen separated by a narrow gap, each with a transparent electrode film (electrode layer) attached. Pressing the surface of the screen presses the electrodes in the film and the glass to come into contact, resulting in the flow of electrical current. The point of contact is identified by detecting this change in voltage.

The advantages of this system include the low-cost manufacture, thanks to its simple structure. The system also uses less electricity than other methods, and the resulting configurations are strongly resistant to dust and water since the surface is covered in film. Since input involves pressure applied to the film, it can be used for input not just with bare fingers, but even when wearing gloves or using a stylus. These screens can also be used to input handwritten text.

Drawbacks include lower light transmittance (reduced display quality) due to the film and two electrode layers; relatively lower durability and shock resistance; and reduced precision of detection with larger screen sizes. (Precision can be maintained in other ways—for example, splitting the screen into multiple areas for detection.)

Capacitive touch panels represent the second most widely used sensing method after resistive film touch panels. Corresponding to the terms used for the above analog resistive touch panels, these also are called analog capacitive touch panels. Aside from standalone LCD monitors, these are often used in the same devices with resistive film touch panels, such as smartphones and mobile phones.

With this method, the point at which the touch occurs is identified using sensors to sense minor changes in electrical current generated by contact with a finger or changes in electrostatic capacity (load). Since the sensors react to the static electrical capacity of the human body when a finger approaches the screen, they also can be operated in a manner similar to moving a pointer within an area touched on screen.

Surface capacitive touch panels are often used in relatively large panels. Inside these panels, a transparent electrode film (electrode layer) is placed atop a glass substrate, covered by a protective cover. Electric voltage is applied to electrodes positioned in the four corners of the glass substrate, generating a uniform low-voltage electrical field across the entire panel. The coordinates of the position at which the finger touches the screen are identified by measuring the resulting changes in electrostatic capacity at the four corners of the panel.

While this type of capacitive touch panel has a simpler structure than a projected capacitive touch panel and for this reason offers lower cost, it is structurally difficult to detect contact at two or more points at the same time (multi-touch).

Projected capacitive touch panels are often used for smaller screen sizes than surface capacitive touch panels. They"ve attracted significant attention in mobile devices. The iPhone, iPod Touch, and iPad use this method to achieve high-precision multi-touch functionality and high response speed.

The internal structure of these touch panels consists of a substrate incorporating an IC chip for processing computations, over which is a layer of numerous transparent electrodes is positioned in specific patterns. The surface is covered with an insulating glass or plastic cover. When a finger approaches the surface, electrostatic capacity among multiple electrodes changes simultaneously, and the position were contact occurs can be identified precisely by measuring the ratios between these electrical currents.

A unique characteristic of a projected capacitive touch panel is the fact that the large number of electrodes enables accurate detection of contact at multiple points (multi-touch). However, the projected capacitive touch panels featuring indium-tin-oxide (ITO) found in smartphones and similar devices are poorly suited for use in large screens, since increased screen size results in increased resistance (i.e., slower transmission of electrical current), increasing the amount of error and noise in detecting the points touched.

Larger touch panels use center-wire projected capacitive touch panels in which very thin electrical wires are laid out in a grid as a transparent electrode layer. While lower resistance makes center-wire projected capacitive touch panels highly sensitive, they are less suited to mass production than ITO etching.

Above, we"ve summarized the differences between the two types of capacitive touch panels. The overall characteristics of such panels include the fact that unlike resistive film touch panels, they do not respond to touch by clothing or standard styli. They feature strong resistance to dust and water drops and high durability and scratch resistance. In addition, their light transmittance is higher, as compared to resistive film touch panels.

On the other hand, these touch panels require either a finger or a special stylus. They cannot be operated while wearing gloves, and they are susceptible to the effects of nearby metal structures.

Surface acoustic wave (SAW) touch panels were developed mainly to address the drawbacks of low light transmittance in resistive film touch panels—that is, to achieve bright touch panels with high levels of visibility. These are also called surface wave or acoustic wave touch panels. Aside from standalone LCD monitors, these are widely used in public spaces, in devices like point-of-sale terminals, ATMs, and electronic kiosks.

These panels detect the screen position where contact occurs with a finger or other object using the attenuation in ultrasound elastic waves on the surface. The internal structure of these panels is designed so that multiple piezoelectric transducers arranged in the corners of a glass substrate transmit ultrasound surface elastic waves as vibrations in the panel surface, which are received by transducers installed opposite the transmitting ones. When the screen is touched, ultrasound waves are absorbed and attenuated by the finger or other object. The location is identified by detecting these changes. Naturally, the user does not feel these vibrations when touching the screen. These panels offer high ease of use.

The strengths of this type of touch panel include high light transmittance and superior visibility, since the structure requires no film or transparent electrodes on the screen. Additionally, the surface glass provides better durability and scratch resistance than a capacitive touch panel. Another advantage is that even if the surface does somehow become scratched, the panel remains sensitive to touch. (On a capacitive touch panel, surface scratches can sometimes interrupt signals.) Structurally, this type of panel ensures high stability and long service life, free of changes over time or deviations in position.

Weak points include compatibility with only fingers and soft objects (such as gloves) that absorb ultrasound surface elastic waves. These panels require special-purpose styluses and may react to substances like water drops or small insects on the panel.

The category of optical touch panels includes multiple sensing methods. The number of products employing infrared optical imaging touch panels based on infrared image sensors to sense position through triangulation has grown in recent years, chiefly among larger panels.

A touch panel in this category features one infrared LED each at the left and right ends of the top of the panel, along with an image sensor (camera). Retroreflective tape that reflects incident light along the axis of incidence is affixed along the remaining left, right, and bottom sides. When a finger or other object touches the screen, the image sensor captures the shadows formed when the infrared light is blocked. The coordinates of the location of contact are derived by triangulation.

While this type differs somewhat from the above touch panels, let"s touch on the subject of electromagnetic induction touch panels. This method is used in devices like LCD graphics tablets, tablet PCs, and purikura photo sticker booths.

This input method for graphics tablets, which originally did not feature monitors, achieves high-precision touch panels by combining a sensor with the LCD panel. When the user touches the screen with a special-purpose stylus that generates a magnetic field, sensors on the panel receive the electromagnetic energy and use it to sense the position of the pen.

Since a special-purpose stylus is used for input, input using a finger or a general-purpose stylus is not possible, and the method has limited applications. Still, this has both good and bad points. It eliminates input errors due to the surrounding environment or unintended screen manipulation. Since the technology was intended for use in graphics tablets, it offers superior sensor precision—making it possible, for example, to change line width smoothly by precisely sensing the pressure with which the stylus is pressed against the screen (electrostatic capacity). This design approach also gives the screen high light transmittance and durability.

The table below summarizes the characteristics of the touch panels we"ve looked at. Keep in mind that even in devices based on the same sensing method, performance and functions can vary widely in the actual products. Use this information only as an introduction to general product characteristics. Additionally, given daily advances in touch-panel technological innovations and cost reductions, the information below is only a snapshot of current trends as of September 2010.

Each touch-panel type offers its own strengths and weaknesses. No single sensing method currently offers overwhelming superiority in all aspects. Choose a product after considering the intended use and environmental factors.

This website is using a security service to protect itself from online attacks. The action you just performed triggered the security solution. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data.

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Responsible for performing installations and repairs (motors, starters, fuses, electrical power to machine etc.) for industrial equipment and machines in order to support the achievement of Nelson-Miller’s business goals and objectives:

• Perform highly diversified duties to install and maintain electrical apparatus on production machines and any other facility equipment (Screen Print, Punch Press, Steel Rule Die, Automated Machines, Turret, Laser Cutting Machines, etc.).

• Provide electrical emergency/unscheduled diagnostics, repairs of production equipment during production and performs scheduled electrical maintenance repairs of production equipment during machine service.

Accidental Damage is any damage due to an unintentional act that is not the direct result of a manufacturing defect or failure. Accidental damage is not covered under the standard warranty of the product. Such damage is often the result of a drop or an impact on the LCD screen or any other part of the product which may render the device non-functional. Such types of damage are only covered under an Accidental Damage service offering which is an optional add-on to the basic warranty of the product. Accidental Damage must not be confused with an occasional dead or stuck pixel on the LCD panel. For more information about dead or stuck pixels, see the Dell Display Pixel Guidelines.

No, accidental damage is covered for Dell computers or monitors which are covered under the Accidental Damage Service offering for that specific product.

For more information about Dell Limited Hardware Warranty and Dell"s Accidental Damage service offering, see the Dell Warranty & Support Services page.

NOTE: Other damages may be considered customer induced if determined by Dell Technical Support, an on-site field engineer, or at the mail-in repair center.

The LCD glass on the display is manufactured to rigorous specifications and standards and will not typically crack or break on its own under normal use. In general, cracked, or broken glass is considered accidental damage and is not covered under the standard warranty.

Internal cracks typically occur due to excessive force on the screen. This can be the result of some object hitting the screen, a drop, attempting to close the lid while an object is on the keypad area, or even holding the laptop by its screen.

Spots typically occur due to an external force hitting the screen causing damage to the LCD panel"s backlight assembly. While the top layer did not crack or break, the underlying area was compressed and damaged causing this effect.

If your Dell laptop LCD panel has any accidental damage but the laptop is not covered by the Accidental Damage service offering, contact Dell Technical Support for repair options.

Dell monitors cannot be repaired by an on-site field engineer or at the mail-in repair center. If you notice any damage to the monitor, you must purchase a new monitor.

Laptop users can strive to make the most of their laptops to maximize stability, longevity, and usability. Understanding and implementing a few best practices for the safe handling of their laptop will enable them to enjoy their laptop for many years to come. For more information, see the Dell knowledge base article Dell Laptop Best Practices for Care, Use, and Handling.

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Keywords:Ensure perfect adherence of anti-glare (AG) films to LCD, adhere anti-reflex (AR) films to LCD, using optically clear adhesive (OCA) in touchscreen manufacturing, diagnosis of functional film adherence, fuji prescale tests in functional film adherence

Summary:Adhering functional films to LCD screens such as anti-glare (AG), anti-reflex (AR) as well as using  optically clear adhesive (OCA) in touchscreens requires uniform pressure to avoid air bubbles, flexing, skewing and other film displacements. Using the Fuji Prescale Ultra-Low Pressure film helps in diagnosing and eliminating any adherence problems.

With the explosive spread of LCD devices on the market, companies look for ways to make their product better in any possible way. For this reason, manufacturers add various functional films to various LCD devices:

Improving visibility and durability of LCD screens involves adhering of Anti-Reflex (AR) films, Anti-Glare (AG) films. Producing touchscreen devices requires using optically clear adhesives to add the resistance or capacitive touch-sensitive films. All these functional films must be flawlessly joined with the base plate to ensure optimal visibility of the displayed information on the LCD.

The method of adhering functional films to the base plate uses rollers that must exert equal pressure throughout the contacting surface so that the functional film is evenly adhered onto the plate. However, in practice, ensuring even pressure is not easy. The larger the adhering surface, the larger the problems.

In some cases, the roller axis can deviate from its ideal perpendicular aligmnent to the plate"s movement vector. This can cause the functional layer to get skewed or wrinkled.

Also, if the roler axis is not ideally parallel to the base plate, the roller will exert more pressure on one end, and lesser adhesion pressure on the other side of the base plate. This can cause air bubbles or poor adhesion of the functional screen.

In order to avoid any imperfections during the manufacturing process, technicians must regularly monitor the roller-cover glass alignment to ensure proper adhesion of the functional films.

The best way to measure alignment is to measure the tactile pressure that the drum exerts on the cover glass using the Fuji Prescale Ultra Low Pressure (LLLW) prescale film, as shown on the illustration below:

The Fuji Prescale film is placed between the cover glass and roller. The roller then rotates to cover the entire surface of the cover glass. This will develop the Fuji Prescale film which then can offer easy and accurate visual inspection, or it can be fed into the FPD-8010E Pressure Mapping System for precise pressure measurement and visualization.

In this case, the roller was not exerting the nominal pressure throughout the surface. Although the pressure was enough to achieve adhesion of the functional layer, the lack of binding pressure resulted in poor adhesion of the functional layer. This defect will only be discovered during the lifetime of the product, which can result in material loss due to warranty claims.

Thanks to the timely usage of the Fuji Prescale film, this manufacturer ensures optimal production quality of the LCD assembly as well as standardized LCD quality throughout the manufactured volume.

Our final project is to design and build a portable blood pressure monitor device that can measure a user"s blood pressures and heart rate through an inflatable hand cuff. The device is consisted of three main parts: external hardwares (such as cuff, motor, valve, and lcd), analog circuit, and microcontroller. The anolog circuit converts the pressure value inside the cuff into readable and usable analog waveforms. The MCU samples the waveforms and performs A/D convertion so that further calculations can be made. In addition, the MCU also controls the operation of the devices such as the button and lcd display. Since we have the word "portable" in our title, for sure all of the components are put together in one package which allows a user to take it anywhere and perform a measurement whenever and wherever he/she wants.

It is undeniable that nowadays people are more aware of the health conditions. One of the most widely used methods to test the health conditions of an individual is to measure his/her blood pressures and heart rate. We, as ones of those who are concerned about their health, decided to work on this subject matter because we would like to build something that is useful and useable in real life.

Usually when the doctor measures the patient"s blood pressure, he will pump the air into the cuff and use the stethoscope to listen to the sounds of the blood in the artery of the patient"s arm. At the start, the air is pumped to be above the systolic value. At this point, the doctor will hear nothing through the stethoscope. After the pressure is released gradually, at some point, the doctor will begin to hear the sound of the heart beats. At this point, the pressure in the cuff corresponds to the systolic pressure. After the pressure decreases further, the doctor will continue hearing the sound (with different characteristics). And at some point, the sounds will begin to disappear. At this point, the pressure in the cuff corresponds to the diastolic pressure.

To perform a measurement, we use a method called �oscillometric�. The air will be pumped into the cuff to be around 20 mmHg above average systolic pressure (about 120 mmHg for an average). After that the air will be slowly released from the cuff causing the pressure in the cuff to decrease. As the cuff is slowly deflated, we will be measuring the tiny oscillation in the air pressure of the arm cuff. The systolic pressure will be the pressure at which the pulsation starts to occur. We will use the MCU to detect the point at which this oscillation happens and then record the pressure in the cuff. Then the pressure in the cuff will decrease further. The diastolic pressure will be taken at the point in which the oscillation starts to disappear.

The diagram above shows how our device is operated. The user will use buttons to control the operations of the whole system. The MCU is the main component that controls all the operations such as motor and valve control, A/D conversion, and calculation, until the measurement is completed. The results then are output through and LCD screen for the user to see.

Since the output voltage of the pressure transducer is very small, we have to amplify the signal for further processing. We use the instrumentation amplifier AD620 from Analog Devices. The resistor R G is used to determine the gain of the amplifier according to the equation

The band-pass filter stage is designed as a cascade of the two active band-pass filters. The reason for using two stages is that the overall band-pass stage would provide a large gain and the frequency response of the filter will have sharper cut off than using only single stage. This method will improve the signal to noise ratio of the output. The schematics for both filters are shown in figure 3.

The ac coupling stage is used to provide the DC bias level. We want the DC level of the waveform to locate at approximately half Vdd, which is 2.5 V. The schematic for AC coupling stage is shown in figure 4. Given this bias level, it is easier for us to process the AC signal using the on-chip ADC in the microcontroller.

The AC output from this stage will be passed on to the analog-to-digital converter in the Mega32 microcontroller. The image from the laboratory bench is shown in figure 5. We can see that it is very nice and clean.

The block diagram for the operating control is consisted of a total of 7 states. We first start at the START state where the program waits for the user to push the white button of the device. Once the white button has been pushed, the measurement process begins by inflating the hand cuff. While the cuff is being inflated, if the user feels very uncomfortable or painful, he/she can push the grey button(emergency button) to stop the motor, quickly deflate the cuff and stop the measurement. This will ensure that the safety of the user is well maintained while using the device. Anyhow, if the cuff-inflating procedure goes smoothly, the air will be pumped into the cuff until the pressure inside the cuff reaches 160 mmHg. After that, the motor will be stopped and the air will be slowly released from the cuff. Again, at this point, the user can abort the process by pressing grey button. Once the MCU has obtained the values of systolic, diastolic and heart rate, the valve will be open to release air from the cuff quickly. Then it will report the result of the measurement by displaying the obtained data on the LCD screen. After that if the black button is pushed the program will return to the START state again waiting for the next measurement. Note that if the emergency button is pushed, the black button needs to be pushed in order to return to the start state.

Once the motor pumps the air into the cuff until the pressure exceeds 160 mmHg, the motor then stops pumping more air and the cuff is deflated through the slightly-opened valve. The pressure in the cuff starts decreasing approximately linearly in time. At this point, the program enters the measurement mode. The MCU will looks at the AC signal through the ADC0 pin and determines the systolic, diastolic pressure values and the heart rate of the user respectively. For this project, we perform the measurement using the oscillometric method, in which the program monitors the tiny pulsations of the pressure in the cuff. The state diagram of the measurement is shown in figure 7

After the motor pumps the pressure up to 160 mmHg which is approximately more than the systolic pressure of normal healthy people, the cuff starts deflating and the program enters Sys_Measure state. In this state, the program will looks at the AC waveform from ADC0 pin. When the pressure in the cuff decreases to a certain value, the blood begins to flow through the arm. At this time if we look at the oscilloscope, we will see the onset of the oscillation. The systolic pressure can be obtained at this point.

The way we program this is that we set a threshold voltage of 4V for the AC waveform. At the start, there is no pulse and the voltage at the ADC0 pin is constant at approximately 2.5 V. Then when the pressure in the cuff decreases until it reaches the systolic pressure value, the oscillation starts and grows. We then count the number of pulses that has maximum values above the threshold voltage. If the program counts up to 4, the program enters the Sys_cal state. At this state, the program records the DC voltage from pin ADC1. Then it converts this DC voltage value to the pressure in the cuff to determine the systolic pressure of the patient.

From the transfer characteristic of the pressure transducer and the measured gain of the DC amplifier, we can determine the systolic pressure by looking at the DC voltage of the ADC1 pin. We will explain the conversion procedure here. Let"s the DC voltage that we read off of the ADC1 pin be �DC_voltage", and the gain of the DC amplifier be �DC_gain". Then the differential voltage that comes out of the DC amplifier is calculated as

After the program finished calculating the systolic pressure, then it starts monitoring the pulse rate of the patient. We choose to determine the pulse rate right after determining the systolic pressure because at this point the oscillation of the waveform is strongest. The program samples the AC waveform every 40 millisecond. It then records the time interval when the values of the AC waveform cross the voltage value of 2.5 volts. The program then takes the average of five time intervals so that the heart rate will be as accurate as possible. The variable used for counting the number of time intervals is count_average as shown in the state diagram. After the heart rate is determined, the program then enters the Dias_measure state, in which it tries to measure the diastolic pressure of the patient.

After the pulse rate is determined, the program enters the Dias_Measure state. In this state, the program is still sampling the signal at every 40 millisecond. We then define the threshold for the diastolic pressure. While the cuff is deflating, at some point before the pressure reaches diastolic pressure, the amplitude of the oscillation will decrease. To determine the diastolic pressure, we record the DC value at the point when the amplitude of the oscillation decreases to below the threshold voltage. This is done by looking at the time interval of 2 seconds. If the AC waveform does not go above the threshold in 2 seconds, it means the amplitude of the oscillation is actually below the threshold. The DC value can then be converted back to the pressure in the arm cuff using the same procedure as described in the Systolic Pressure Measurement section.

Please note that determining the diastolic pressure is quite difficult and ambiguous since the voltage threshold varies from person to person. Thus, we have to adjust the voltage threshold that we use so that the value of diastolic pressure that we obtain corresponds to the known value we usually get when we measure it using the available commercial product.

After the program finishes calculating the diastolic pressure, it will display the information acquired from the measurement on the LCD. Then the program will open up the valve and the cuff will deflate quickly. The measurement is now finished.

The results of the project are as expected and satisfactory to us. If the user stays still during the operation, the device can measure blood pressures(both systolic and diastolic) and heart rate without any problem.

From the start until all the measurements are done, it takes about 1.5 minutes. However, this also depends on each individual and how the cuff is worn. For each person, the amplitude of the waveforms may differ causing the operating time to vary. Still, the difference is small and is usually within 10 seconds.

As mentioned earlier, all the measurements are mainly dependent on the waveforms from the circuit and the pressure sensor is very sensitive to even a slight movement of the user. As a result, it is possible that sometimes the device fails to obtain the desired data, especially if the user does not stay still or wear the cuff improperly.

Regarding the three result values (systolic, diastolic and heart rate), some of them has more success rate than the others. For the heart rate, the success rate is very high for getting an accurate value. To find the heart rate, we need to find the period of the AC waveform. And since the period of heart rate stays pretty much constant through out the measurement, it is relatively easy to obtain an accurate result. To find the pressure values, however, are harder because they depend on the amplitude of the waveform, and the amplitude varies a lot during the measurement. However, if the user stays still and wears the cuff right, the measurement are usually successful 8 time out of 10 tries (80% success rate).

Another topic that is worth mentioning is that the method of measurement that we used is called the oscillometric method. It is usually deployed in commercial products due to the reliability. However, this method is not as accurate as the auscultatory method, in which the doctor uses the mocrophone to listen to the noise in the artery.

Since this is a medical instrumentation device, the safety of the user is the first concern to us. The cuff while driven by a 5 volts motor can squeeze the arm really hard and cause injury if being used improperly. So in our device we have 3 levels of security, making sure that the operation can be aborted by the user at anytime.

For the first safety design, the microcontroller is programmed in the way such that if the pressure in the cuff is greater than 160 mmHg, the motor will stop. For most people, the pressure at 160 mmHg will only cause a little discomfort to the arm. This desgin makes sure that the pressure inside the cuff will never exceed the maximum limit of 160 mmHg.

The second safety design is to provide an emergency button for the user. While the motor is pumping and the cuff is being inflated, if the user encounters too much discomfort or pain, he/she can press this button to stop the operation immediately. The motor will be stopped and the valve will be opened to release the air out of the cuff.

However, we still think that only a pushbutton is not enough for the safety of the user. This is because the emergency button still relies on the operating system of the program in the MCU. Even though we have no bug in our program, if something goes wrong with the MCU or the button connections, there is a possibility that the emergency button becomes unusable. So we agree that we must have another swtich that control the device physically. This switch must be able to disconnect the circuit from the power supply immediately. This way it is certain that the user will be able to stop the operation even when the emergency button does not work. And this switch is the on-off power switch that we have on the device.

Other than the cuff and motor concerns, our project is very safte to use because it is very well packaged in a plastic enclosure. The device is run by low-voltage(9 volts) battery which cannot cause any major harm to human body.

Since our project only performs measurements on an individual (user), there should not be any interference produced by the device besides the sound of the motor running (which is very quiet compared to regular motors).

Our project should be useable to most adults, since it is basically a regular blood pressure moniotor sold in the markets nowadays. The instructions LCD screen are pretty straight forward and easy to understand. Since this device is built to be portable, it can be used anywhere and any time as long as the battery still has power.

The cuff that we use is appropriate for the average adult arm size (9-13 inches in circumference). Thus the arm size that is out of this range may not give the accurate measurement. Due to our budget constraints, we do not have many cuff size for our project

For people with health problem, especially on blood pressure or heart, it is not recommended to use this device, because we have only tested it with healthy people. Therefore, for the maximum safety of the user, this device can only be used by the people who do not have medical problems on heart and circulartory system.

Most of the designs that we proposed before we started the project are met in our final result. In fact, we are really happy and satisfied with the final result of our project. The measurements are acceptably accurate (please see "Accuracy" section in results part). The operations of the device are reliable and have not produced any major problems. The power consumption of the device is decent as we have already tried lots of measurements(more than 20) and the set of two 9-volt batteries has not died yet.

Regarding the batteries and power consumption, we encountered a big problem in this issue while testing the device. At the first place, we used one battery to power the MCU board, and the other to power the circuit, valve and motor. However after a couple of tries, the battery that powered the circuit and motor lost its power and could not provide a constant voltage during the measurement. In other words, the voltage across that battery drops constantly as the motor runs. As a result, the voltage that feeds all the chips in the circuit are not high enough (the AD620 and OPA2277 requires 5V and -5V)

So we fixed this problem by separating the battery that runs the valve and motor from the rest of the circuit. Then we use the battery that supplies the MCU board to power the circuit instead. Now that the battery that supplies the valve and the motor is separated, it ensures that there will be no voltage drop in the circuit while the motor is running. This way, the power consumption of the 2 batteries will be more balanced, since the circuit and the MCU do not consume much power.

There is only one proposed feature that is missing from our project. It is the option that let the user to output the pulse waveform(AC component) on the TV. If we want to output the signal on TV, we will need another Mega32 and a pc board. However, due to the limited budget of $50, this could not be done.

All the circuits and the codes are originally designed by us. The topologies of the circuits are the one discussed in standard textbooks. We do not use other people"s codes or circuit topologies from other people designs. Thus, we are sure that we do not violate any intellectual property of the existing design.

For this project, both of us work very closely with each other and spend more than 50 hours in the lab. For the design of analog circuit, we worked on the design together during the first two weeks of the final project. Then we split up the tasks of writing the code. Warut is responsible for writing the motor and valve control codes. Woradorn is responsible for the codes for the measurement of the metrics (systolic, diastolic and heart rate).

After we finished the design, we split up the task for soldering the components into the proto-board. Warut is responsible for soldering the proto-board for the microcontroller. Woradorn is responsible for the soldering of the analog circuit board. Furthermore, we both contribute equally to the soldering of the supply circuit (all the voltage regulators and battery). For the package design, Warut takes care all of that.