Total error in the analysis of the pressure sensor, we must first consider the source of an error analysis of the factors that lead to these errors, and then think of ways to reduce these errors, improve the overall performance of the sensor. This article lists the sources of error which affect the pressure sensor performance?
The total error of the pressure sensor, you should use the following definitions of error. Decision you have selected the extent of the pressure sensor-specific error, see this directory specification of the sensor.
In a particular user application, some nominal indicators can be reduced or eliminated, for example, if a pressure sensor is used in the inner half of the predetermined temperature range, then the temperature error can be reduced by half, if the use of the auto-zero techniques, zero offset, and zero drift error can be eliminated.
The zero offset is the same pressure on both sides of the diaphragm of the sensor output.
Span is the algebraic difference between the output endpoint. Usually two endpoints zero and full scale.
The zero point temperature drift is caused by temperature changes of the pressure sensor zero change. Zero offset error is not predictable, because each device can be offset upward or downward change in temperature will cause the entire output curve along the voltage axis offset up or down.
Sensitivity temperature offset is the pressure sensor sensitivity variation caused by temperature changes, temperature changes will cause the change of the slope of the sensor output curve.
The linearity error is at the desired pressure range of the sensor output curve and a deviation of the calibration straight line, a method for computing linear error is the least-squares on the straight line of best fit of the data points from mathematical.
Another method is the the end BP linearity (TBL) or endpoint linearity. TBL decision by a straight line drawn between the data points of the second end (L1) in the output curve. Subsequently a vertical line to the output curve from the line L1, and select the intersecting data points in order to achieve the maximum length of a perpendicular line, the length of the perpendicular line represents the end of BP linearity error.
Repeatability error in the other conditions remain constant, continuous together with any given input pressure deviation in output readings.
Hysteresis error is usually expressed as the mechanical hysteresis and temperature hysteresis combination of error.
The mechanical hysteresis: refers to the output sensor error in one to a given input pressure (increased, decreased different process).
Temperature hysteresis in a temperature cycle before and after the output in the exact input pressure deviation.
The ratio of the amount of change is in the other conditions remain constant sensor output ratio of the power supply voltage, the ratio of the change in error is the change in this ratio, usually expressed as a percentile of the range of the pressure sensor.
Each pressure sensor error sources sum up the above so many, some systematic errors, some random errors, some errors can be eliminated, to find a way to be eliminated through improved technologies, to ensure that the sensor has good output.
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2013年5月8日星期三
Comprehensive Understanding of Touch Phone Touch Screen
The first mobile phone was born in 1973 in the United States, Martin Cooper invented by Motorola's engineers and technicians. This mobile phone Martin Cooper also can not be called a phone, because his foot two bricks, "mobile phone" in the true sense of the launch in 1987, and since then, the volume of mobile phones more and more on technologies and applications used in mobile phones more and more rich. After 2006, the subversive phone upgrade getting smaller and smaller, but another mobile application revolution continues to spread, this is the popularity of mobile phones touch operation.
2008 to 2009 the global touch phone flourishing moment the mainstream touch interface has more than nine kinds of these innovative designs are receiving the baptism of the market. After the selection of the Ebb Tide, and ultimately the strong win, now is the time we can see the whole market overview. China Mobile launched special large-scale thematic interpretation of the mainstream mobile phone touch operation platform.
First, capacitive touch screen with resistive touch screen
1. capacitive touch screen introduction:
The four sides of the touch screen, capacitive touch screen plated with a narrow electrode, a low-voltage alternating electric field is formed in the conductive body. The touch screen, the body farm, fingers conductor layer will form a coupling capacitor, issued by the four sides of the electrode current will flow to the contact, and the current strength of the finger to the electrode is proportional to the distance, touch screen controller calculates the ratio of the currents and strong or weak, to accurately calculate the position of the touch point.
The capacitive touch screen is a special metal layer of transparent conductive material in the surface of the glass paste. When the finger touch on the metal layer, the capacitance of the contacts occurs, such that the associated oscillator frequency is changed, the change can be determined by measuring the frequency of the touch position obtained information.
Capacitive touch screen defects:
Varies due to the capacitance change with temperature, humidity or ground to different circumstances and therefore its stability is poor, and tends to produce a drift phenomenon. The touch screen is suitable for the commissioning phase of the system development.
2. resistive touch screen basic principles:
The use of pressure-sensitive resistive touch screen control. A main part of the resistive touch screen resistive films screen is a very complex piece with the display surface, which is a multi-layered composite film as primary layer of glass or hard plastic plate, the surface coated with a layer of transparent metal oxide (transparent conductive resistance) of the conductive layer, above and then cover with a layer of outer surface hardening treatment, smooth plastic layer anti-rub, and its inner surface is also coated with a layer of coating, between them, have many of the small (less than 1/1000 inch) transparent The isolation point the two conductive layers separated by insulation. When the finger touches the screen, the two conductive layers on the touch point there will be a contact resistance change signal is generated on the X and Y directions, and then send the touch screen controller. The controller detects the contact and to calculate the position (X, Y), according to the operation of the simulated mouse. This is the basic principle of the resistive touch screen technology.
Second, the resolution
1. Screen resolution:
The screen resolution is to determine how much information settings displayed on the screen, to measure the horizontal and vertical pixels. The screen resolution is low (for example, 640 x 480), the items displayed on the screen, but the relatively large size. Screen resolution (example 1600 x 1200), the items displayed on the screen, but the size is relatively small.
2. Definition of WVGA:
Digital products a screen material the VGA of another form than the VGA resolution, alias: Wide VGA resolution of 800 x 480 pixels. To expand the resolution of VGA (640 x 480). Used in PDA and cell phones, because a lot of the width of the page is 800 WVGA screen will be more appropriate and in browsing the web, it can be said the resolution trend of handheld devices in the future.
3. Definition of QVGA:
The QVGA QuarterVGA "refers to one of the VGA size. Is output on the LCD screen resolution is 240 x 320 pixels. It should be noted that some of the media as a QVGA screen with TFT and TFD LCD material is the same thing wrong the QVGA screen saying common with some of Japan's mobile phone power supply, Microsoft PPC operating system for smart phones screen mostly 320 x 240 pixel QVGA screen.
The so-called the QVGA LCD technology, is output on the LCD screen resolution is 240 x 320 LCD output mode. In fact, this resolution does not matter the size of the screen itself. For example, if the 2.1-inch LCD display screen can display 240 x 320 resolution image, it is called "QVGA 2.1-inch LCD screen; 3.8-inch LCD screen can display 240 x 320 image, called" QVGA 3.8-inch liquid crystal display ", although both of these cases have the same resolution, but due to the size of the type of the actual visual effect type, generally small screen of a screen will naturally small.
2008 to 2009 the global touch phone flourishing moment the mainstream touch interface has more than nine kinds of these innovative designs are receiving the baptism of the market. After the selection of the Ebb Tide, and ultimately the strong win, now is the time we can see the whole market overview. China Mobile launched special large-scale thematic interpretation of the mainstream mobile phone touch operation platform.
First, capacitive touch screen with resistive touch screen
1. capacitive touch screen introduction:
The four sides of the touch screen, capacitive touch screen plated with a narrow electrode, a low-voltage alternating electric field is formed in the conductive body. The touch screen, the body farm, fingers conductor layer will form a coupling capacitor, issued by the four sides of the electrode current will flow to the contact, and the current strength of the finger to the electrode is proportional to the distance, touch screen controller calculates the ratio of the currents and strong or weak, to accurately calculate the position of the touch point.
The capacitive touch screen is a special metal layer of transparent conductive material in the surface of the glass paste. When the finger touch on the metal layer, the capacitance of the contacts occurs, such that the associated oscillator frequency is changed, the change can be determined by measuring the frequency of the touch position obtained information.
Capacitive touch screen defects:
Varies due to the capacitance change with temperature, humidity or ground to different circumstances and therefore its stability is poor, and tends to produce a drift phenomenon. The touch screen is suitable for the commissioning phase of the system development.
2. resistive touch screen basic principles:
The use of pressure-sensitive resistive touch screen control. A main part of the resistive touch screen resistive films screen is a very complex piece with the display surface, which is a multi-layered composite film as primary layer of glass or hard plastic plate, the surface coated with a layer of transparent metal oxide (transparent conductive resistance) of the conductive layer, above and then cover with a layer of outer surface hardening treatment, smooth plastic layer anti-rub, and its inner surface is also coated with a layer of coating, between them, have many of the small (less than 1/1000 inch) transparent The isolation point the two conductive layers separated by insulation. When the finger touches the screen, the two conductive layers on the touch point there will be a contact resistance change signal is generated on the X and Y directions, and then send the touch screen controller. The controller detects the contact and to calculate the position (X, Y), according to the operation of the simulated mouse. This is the basic principle of the resistive touch screen technology.
Second, the resolution
1. Screen resolution:
The screen resolution is to determine how much information settings displayed on the screen, to measure the horizontal and vertical pixels. The screen resolution is low (for example, 640 x 480), the items displayed on the screen, but the relatively large size. Screen resolution (example 1600 x 1200), the items displayed on the screen, but the size is relatively small.
2. Definition of WVGA:
Digital products a screen material the VGA of another form than the VGA resolution, alias: Wide VGA resolution of 800 x 480 pixels. To expand the resolution of VGA (640 x 480). Used in PDA and cell phones, because a lot of the width of the page is 800 WVGA screen will be more appropriate and in browsing the web, it can be said the resolution trend of handheld devices in the future.
3. Definition of QVGA:
The QVGA QuarterVGA "refers to one of the VGA size. Is output on the LCD screen resolution is 240 x 320 pixels. It should be noted that some of the media as a QVGA screen with TFT and TFD LCD material is the same thing wrong the QVGA screen saying common with some of Japan's mobile phone power supply, Microsoft PPC operating system for smart phones screen mostly 320 x 240 pixel QVGA screen.
The so-called the QVGA LCD technology, is output on the LCD screen resolution is 240 x 320 LCD output mode. In fact, this resolution does not matter the size of the screen itself. For example, if the 2.1-inch LCD display screen can display 240 x 320 resolution image, it is called "QVGA 2.1-inch LCD screen; 3.8-inch LCD screen can display 240 x 320 image, called" QVGA 3.8-inch liquid crystal display ", although both of these cases have the same resolution, but due to the size of the type of the actual visual effect type, generally small screen of a screen will naturally small.
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