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参数资料
| 型号： | DEMOAPEXSENSOR |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 15/20页 |
| 文件大小： | 0K |
| 描述： | BOARD DESIGN ALTITUDE PRESSURE |
| 标准包装： | 1 |
| 传感器类型： | 加速计，压力，水位，高度计/气压计 |
| 传感范围： | 多范围 |
| 接口： | I²C，SPI，模拟 |
| 灵敏度： | 多重 |
| 电源电压： | 10 V |
| 嵌入式： | 是，MCU，8 位 |
| 已供物品： | 板 |
| 已用 IC / 零件： | MPX2102，MPXV5004G，MPL115A2，MMA7361L |
| 产品目录页面： | 2808 (CN2011-ZH PDF) |
Altimeter Example 2:
A GPS equipped smart-phone loses GPS signal as it enters a building. Knowing the approximate elevation with the GPS, the
beginning ‘zero point’ is 300 m. Entering the building the pressure sensor starts measuring the elevation, and tries to calculate
the height in meters.
Issues in this Example for Consideration:
? When entering a building from outside, a sudden rise in pressure is highly probable. This will send two different scenarios.
It could signify that the user has ‘fallen’ in altitude by several meters (such as jumping off a building or small cliff). Or they
have entered into a building with significant pressurized airflow (typical of an air-conditioned lobby with high air flow).
? Buildings vary on height per a floor. Lobbies of sky-rises have higher ceilings. Hotel accommodation floors tend to have
shorter standard heights. A restaurant located halfway or on top of the building may have a higher ceiling. The main point
is that the altitude in meters does not ideally correspond to floor location.
? Large buildings can be pressurized or not. It depends on building design. Some stadiums for sporting events are
pressurized to keep a fabric roof afloat. Tall high-rises have multiple stages of air-conditioning units. This leads to varied
pressure per a floor depending on that section’s on/off cycle, fan speed, or the air-tight nature of that section. Elevator
shafts also can equalize pressure, or create some pressure change as elevators move up and down.
? Smart use of Altimetry in tall buildings would use building information stored in a ‘smart’ GPS device so the altitude can
translate to floor level. This way location based services, emergency 911, etc. can know which floor the user is located.
MPL115A Miniature Barometer DEMOAPEXSENSOR
The MPL115A is a small 5 x 3 x 1.2 mm digital absolute pressure sensor. It is available in either I 2 C or SPI version. It has a
pressure range of 50 to 115 kPa. This narrower range is more application specific for events occurring in that altitude or in devices
requiring that pressure. In this section, the DEMOAPEXSENSOR’s implementation of the MPL115A and the information
displayed on the APEX is described.
In the Quick Start Guide section, the “Barometer Compensated Pressure Output” describes the compensated Pressure output
of the MPL115A in screen shots of the DEMOAPEXSENSOR.
Barometer Compensated Pressure Output
MPL115A2 Raw Values
6 Coefficients
Compensated Pressure
Press ADC
Temp ADC
74c0 0467
6b40 0428
ao = 3dc4 c11 = f8a0
b1 = bd7a c12 = 2flc
PComp = 9778 kPa
Altitude = 365 m
ENTER for Coefficients
b2 = c299 c22 = 0dc0
Stage 1
Raw Values of Temperature
and Pressure displayed on
Stage 2
Display of 6 coefficients listed
on LCD screen.
Stage 3
Display of Compensated
Pressure output in kPa units.
LCD screen.
The MPL115A’s Implementation is described in detail in the Application Note AN3785; How to Implement the Freescale
MPL115A Digital Barometer. Essentially in the LCD screen shots above, the Raw values of Pressure and Temperature are
displayed in Hexadecimal and Decimal format. Following this, the six coefficients MSB+LSB are shown in Hex format. The
combination of this data (streamed via I 2 C or SPI from the MPL115A) is used at the host MCU to calculate the Pcomp value.
Using eq. 2, the altitude is calculated and shown in meters.
The Pcomp value is the compensated absolute pressure value. This value unlike the analog pressure sensors does not require
any calibration trim, or offset auto zero. The Pcomp spec for the MPL115A is such that the value has an accuracy of ± 1kPa. The
advantage is implementing the sensor and having the compensated pressure readings without any additional calibration etc. on
the customer side.
As stated in AN3785, the MCU has to apply the equation below for Pcomp given that a0, b1, b2, c11, c12, c22 are coefficients
stored in MPL115A registers. Padc and Tadc are the raw ADC values of Pressure and Temperature that are clocked out of
MPL115A digitally.
Pcomp = a0 + ( b1 + cl ? Padc + c12 ? Tadc ) ? Padc + ( b2 + c12 ? Tadc ) ? Tadc
(eq. 3)
AN3956
Sensors
Freescale Semiconductor
15
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DEMO-AT3/4-XX32 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:AT-32032 and AT-41532 demonstration for 800-900 MHz applications |
| DEMO-AT32063 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:860 MHz cascode amplifier |
| DEMO-AT3XX11 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:AT-31011 2400 MHz 2 stage LNA amplifier; can also be used for AT-30511 or AT-32011 |
| DEMO-AT3XX33 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:900 MHz single stage LNA amplifier using AT-32033; circuit can also be used for AT-30533 or AT-31033 |
| DEMO-ATF3616-3 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:2 to 2.4 GHz single stage LNA using ATF-36163 |
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