外文翻译----数字温湿度传感器(SHT1xSHT7x).docx

附录三 外文翻译外文资料SHT1x / SHT7xHumidity & Temperature Sensor - Relative humidity and temperature sensors- Dew point- Fully calibrated, digital output- Excellent long-term stability- No external components required- Ultra low power consumption- Surface mountable or 4-pin fully interchangeable- Small size- Automatic power downSHT1x / SHT7x Product SummaryThe SHTxx is a single chip relative humidity and temperature multi sensor module comprising a calibrated digital output. Application of industrial CMOS processes withpatented micro-machining (CMOSens technology) ensures highest reliability and excellent long term stability. The device includes a capacitive polymer sensing element for relative humidity and a bandgap temperature sensor. Both are seamlessly coupled to a 14bit analog to digital converter and a serial interface circuit on the same chip. This results in superior signal quality, a fast response time and insensitivity to external disturbances (EMC) at a very competitive price.Each SHTxx is individually calibrated in a precision humidity chamber with a chilled mirror hygrometer as reference. The calibration coefficients are programmed into the OTP memory. These coefficients are used internally during measurements to calibrate the signals from the sensors. The 2-wire serial interface and internal voltage regulation allows easy and fast system integration. Its tiny size and low power consumption makes it the ultimate choice for even the most demanding applications.The device is supplied in eith surface-mountable LCC (Leadless Chip Carrier) or as a pluggable 4-pin single-in-line type package. Customer specific packaging options may beavailable on request.Applications_ HVAC_ Automotive_ Consumer Goods_ Weather Stations _ Humidifiers_ Dehumidifiers_ Test & Measurement_ Data Logging_ Automation_ White Goods_ Medical2 Interface SpecificationsFigure 2 Typical application circuit2.1 Power PinsThe SHTxx requires a voltage supply between 2.4 and 5.5 V. After powerup the device needs 11ms to reach its “sleep” state. No commands should be sent before that time.Power supply pins (VDD, GND) may be decoupled with a 100 nF capacitor.2.2 Serial Interface (Bidirectional 2-wire)The serial interface of the SHTxx is optimized for sensor readout and power consumption and is not compatible with I2C interfaces, see FAQ for details.2.2.1 Serial clock input (SCK)The SCK is used to synchronize the communication between a microcontroller and the SHTxx. Since the interface consists of fully static logic there is no minimum SCKfrequency.2.2.2 Serial data (DATA)The DATA tristate pin is used to transfer data in and out of the device. DATA changes after the falling edge and is valid on the rising edge of the serial clock SCK. During transmission the DATA line must remain stable while SCK is high. To avoid signal contention the microcontroller should only drive DATA low. An external pull-up resistor (e.g. 10 k ) is required to pull the signal high. (See Figure 2) Pull-up resistors are often included in I/O circuits of microcontrollers. See Table 5 for detailed IO characteristics.2.2.3 Sending a commandTo initiate a transmission, a “Transmission Start” sequence has to be issued. It consists of a lowering of the DATA line while SCK is high, followed by a low pulse on SCK and raising DATA again while SCK is still high.Figure 3 Transmission Start sequenceThe subsequent command consists of three address bits (only “000” is currently supported) and five command bits. The SHTxx indicates the proper reception of a command by pulling the DATA pin low (ACK bit) after the falling edge of the 8th SCK clock. The DATA line is released (and goes high) after the falling edge of the 9th SCK clock.2.2.4 Measurement sequence (RH and T)After issuing a measurement command (00000101 for RH, 00000011 for Temperature) the controller has to wait for the measurement to complete. This takes approximately 11/55/210 ms for a 8/12/14bit measurement. The exact time varies by up to 15% with the speed of the internal oscillator. To signal the completion of a measurement, the SHTxx pulls down the data line and enters idle mode. The controller must wait for this “data ready” signal before restarting SCK to readout the data. Measurement data is stored until readout, therefore the controller can continue with other tasks and readout as convenient.Two bytes of measurement data and one byte of CRC checksum will then be transmitted. The uC must acknowledge each byte by pulling the DATA line low. Allvalues are MSB first, right justified. (e.g. the 5th SCK is MSB for a 12bit value, for a 8bit result the first byte is not used). Communication terminates after the acknowledge bit of the CRC data. If CRC-8 checksum is not used the controller may terminate the communication after the measurement dat LSB by keeping ack high. The device automatically returns to sleep mode after the measurement and communication have ended. Warning: To keep self heating below 0.1 C the SHTxx should not be active for more than 10% of the time (e.g. max. 2 measurements / second for 12bit accuracy).2.2.5 Connection reset sequenceIf communication with the device is lost the following signal sequence will reset its serial interface:While leaving DATA high, toggle SCK 9 or more times. This must be followed by a “Transmission Start” sequence preceding the next command. This sequence resets theinterface only. The status register preserves its content.Figure 4 Connection reset sequence2.2.6 CRC-8 Checksum calculationThe whole digital transmission is secured by a 8 bit checksum. It ensures that any wrong data can be detected and eliminated.Please consult application note “CRC-8 Checksum Calculation” for information on how to calculate the CRC.2.3 Status RegisterSome of the advanced functions of the SHTxx are available through the status register. The following section gives a brief overview of these features. A more detailed description is available in the application note “Status RegisterFigure 7 Status Register Write Figure 8 Status Register Read2.3.1 Measurement resolutionThe default measurement resolution of 14bit (temperature) and 12bit (humidity) can be reduced to 12 and 8bit. This is especially useful in high speed or extreme low powerapplications.2.3.2 End of BatteryThe “End of Battery” function detects VDD voltages below 2.47 V. Accuracy is 0.05 V2.3.3 HeaterAn on chip heating element can be switched on. It will increase the temperature of the sensor by 5-15 C (9-27 F). Power consumption will increase by 8 mA 5 V.Applications:By comparing temperature and humidity values before and after switching on the heater, proper functionality of both sensors can be verified. In high (95 %RH) RH environments heating the sensor element will prevent condensation, improve response time and accuracyWarning: While heated the SHTxx will show higher temperatures and a lower relative humidity than with no heating.3 Converting Output to Physical Values3.1 Relative HumidityTo compensate for the non-linearity of the humidity sensor and to obtain the full accuracy it is recommended to convert the readout with the following formula1:RHlinear = c1 +c2 SORH +c3 SORH2 Table 6 Humidity conversion coefficients Table 7 Temperature compensation coefficientThe humidity sensor has no significant voltage dependencyFigure 10 Conversion from SORH to relative humidity3.1.1 Humidity Sensor RH/Temperature compensationFor temperatures significantly different from 25 C (77 F) the temperature coefficient of the RH sensor should be considered:RHtrue = (TC - 25)(t1 +t2 SORH)+RHlinear3.2 TemperatureThe bandgap PTAT (Proportional To Absolute Temperature) temperature sensor is very linear by design. Use the following formula to convert from digital readout totemperature:Temperatur e = d1 +d2 SOTTable 8 Temperature conversion coefficientsFor improved accuracies in extreme temperatures with more computation intense conversion formulas see application note “RH and Temperature Non-Linearity Compensation3.3 DewpointSince humidity and temperature are both measured on the same monolithic chip, the SHTxx allows superb dewpoint measurements. See application note “Dewpoint calculation” for more.4 Applications Information4.1 Operating and Storage ConditionsFigure 11 Recommended operating conditionsConditions outside the recommended range may temporarily offset the RH signal up to 3 %RH. After return to normal conditions it will slowly return towards calibration state by itself. See 4.3 “Reconditioning Procedure” to accelerate this process. Prolonged exposure to extreme conditions may accelerate ageing.4.2 Exposure to ChemicalsChemical vapors may interfere with the polymer layers used for capacitive humidity sensors. The diffusion of chemicals into the polymer may cause a shift in both offset and sensitivity. In a clean environment the contaminants will slowly outgas. The reconditioning procedure described below will accelerate this process. High levels of pollutants may cause permanent damage to the sensing polymer.4.3 Reconditioning ProcedureThe following reconditioning procedure will bring the sensor back to calibration state after exposure to extreme conditions or chemical vapors. 80-90 C (176-194F) at 74 %RH for 48h (re-hydration)4.4 Temperature EffectsThe relative humidity of a gas strongly depends on its temperature. It is therefore essential to keep humidity sensors at the same temperature as the air of which therelative humidity is to be measured.If the SHTxx shares a PCB with electronic components that give off heat it should be mounted far away and below the heat source and the housing must remain well ventilated. To reduce heat conduction copper layers between the SHT1x and the rest of the PCB should be minimized and aslit may be milled in between (see figure 13).4.5 MembranesA membrane may be used to prevent dirt from entering the housing and to protect the sensor. It will also reduce peak concentrations of chemical vapors. For optimal response times air volume behind the membrane must be kept to a minimum. For the SHT1x package Sensirion recommends the SF1 filter cap for optimal IP67 protection.4.6 LightThe SHTxx is not light sensitive. Prolonged direct exposure to sunshine or strong UV radiation may age the housing.4.7 Materials Used for Sealing / MountingMany materials absorb humidity and will act as a buffer, increasing response times and hysteresis. Materials in the vicinity of the sensor must therefore be carefully chosen.Recommended materials are: All Metals, LCP, POM (Delrin), PTFE (Teflon), PE, PEEK, PP, PB, PPS, PSU, PVDF, PVF For sealing and gluing (use sparingly): High filled epoxy for electronic packaging (e.g. glob top, underfill), and Silicone. Outgassing of these materials may also contaminate the SHTxx (cf. 4.2). Store well ventilated after manufacturing or bake at 50C for 24h to outgas contaminants before packing.4.8 Wiring Considerations and Signal IntegrityCarrying the SCK and DATA signal parallel and in close proximity (e.g. in wires) for more than 10cm may result in cross talk and loss of communication. This may be resolved by routing VDD and/or GND between the two data signals. Please see the application note “ESD, Latchup and EMC” for more information. Power supply pins (VDD, GND) should be decoupled with a 100 nF capacitor if wires are used.4.9 ESD (Electrostatic Discharge)ESD immunity is qualified according to MIL STD 883E, method 3015 (Human Body Model at 2 kV). Latch-up immunity is provided at a force current of 100 mA with Tamb = 80 C according to JEDEC 17. See application note “ESD, Latchup and EMC” for more information.5 Important Notices5.1 Warning, personal injuryDo not use this product as safety or emergency stop devices or in any other application where failure of the product could result in personal injury. Failure tocomply with these instructions could result in death or serious injury. Should buyer purchase or use SENSIRION AG products for any such unintended or unauthorized application, Buyer shall indemnify and hold SENSIRION AG and its officers, employees, subsidiaries, affiliates and distributors harmless against all claims, costs, damages and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SENSIRION AG was negligent regarding the design or manufacture of the part.5.2 ESD PrecautionsThe inherent design of this component causes it to be sensitive to electrostatic discharge (ESD). To prevent ESD-induced damage and/or degradation, take normal ESD precautions when handling this product. See application note “ESD, Latchup and EMC” for moreinformation.5.3 WarrantySENSIRION AG makes no warranty, representation or guarantee regarding the suitability of its product for any particular purpose, nor does SENSIRION AG assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability, including without limitation consequential or incidental damages. “Typical” parameters can and do vary in different applications. All operating parameters,including “Typical” must be validated for each customer applications by customers technical experts. SENSIRION AG reserves the right, without further notice, to change the product specifications and/or information in thisdocument and to improve reliability, functions and design.数字温湿度传感器(SHT 1x/ SHT 7x)_ 相对湿度和温度测量 _ 兼有露点_ 全标定输出，无需标定即可互换使用_ 卓越的长期稳定性_ 两线制数字接口，无需额外部件_ 基于请求式测量，因此低能耗_ 表面贴片或4 针引脚安装_ 超小尺寸_ 自动休眠SHT1x / SHT7x 产品概述SHTxx 系列产品是一款高度集成的温湿度传感器芯片， 提供全标定的数字输出。它采用专利的CMOSens 技术，确保产品具有极高的可靠性与卓越的长期稳定性。传感器包括一个电容性聚合体测湿敏感元件、一个用能隙材料制成的测温元件，并在同一芯片上，与14 位的A/D 转换器以及串行接口电路实现无缝连接。因此，该产品具有品质卓越、超快响应、抗干扰能力强、极高的性价比等优点。每个传感器芯片都在极为精确的湿度腔室中进行标定，以镜面冷凝式湿度计为参照。校准系数以程序形式储存在OTP 内存中，在标定的过程中使用。两线制的串行接口与内部的电压调整，使外围系统集成变得快速而简单。微小的体积、极低的功耗，使其成为各类应用的首选。产品提供表面贴片 LCC 或4 针单排引脚封装。特殊封装形式可根据用户需求而提供。应用领域 框图 _ 暖通空调HVAC _ 汽车_ 消费品_气象站_湿度调节器_除湿器_ 测试及检测设备_ 数据记录器_ 自动控制_ 家电_ 医疗2 接口说明图 2 典型应用电路2.1 电源引脚SHTxx 的供电电压为2.45.5V。传感器上电后，要等待11ms 以越过“休眠”状态。在此期间无需发送任何指令。电源引脚（VDD，GND）之间可增加一个100nF 的电容，用以去耦滤波。2.2 串行接口 (两线双向)SHTxx 的串行接口，在传感器信号的读取及电源损耗方面，都做了优化处理；但与I2C 接口不兼容，详情参见 FAQ2.2.1 串行时钟输入 (SCK)SCK 用于微处理器与SHTxx 之间的通讯同步。由于接口包含了完全静态逻辑，因而不存在最小SCK 频率。2.2.2 串行数据 (DATA)DATA 三态门用于数据的读取。DATA 在SCK 时钟下降沿之后改变状态，并仅在SCK 时钟上升沿有效。数据传输期间，在SCK 时钟高电平时，DATA必须保持稳定。为避免信号冲突，微处理器应驱动DATA 在低电平。需要一个外部的上拉电阻（例如：10k）将信号提拉至高电平（参见图2）。上拉电阻通常已包含在微处理器的I/O 电路中。详细的IO特性，参见表 5。2.2.3 发送命令用一组“ 启动传输”时序，来表示数据传输的初始化。它包括：当SCK 时钟高电平时DATA 翻转为低电平，紧接着SCK 变为低电平，随后是在SCK 时钟高电平时DATA 翻转为高电平。图 3 启动传输 时序后续命令包含三个地址位（目前只支持“000”），和五个命令位。SHTxx 会以下述方式表示已正确地接收到指令：在第8 个SCK 时钟的下降沿之后，将DATA 下拉为低电平（ACK 位）。在第9 个SCK 时钟的下降沿之后，释放DATA（恢复高电平）。表2 SHT控制命令代码命令代码含义00011测量温度00101测量湿度00111读内部状态寄存器11110复位命令，使内部状态寄存器恢复默认值，下一次命令前至少等11ms其他保留2.2.4 测量时序(RH 和 T)发布一组测量命令（00000101表示相对湿度RH，00000011表示温度T）后，控制器要等待测量结束。这个过程需要大约11/55/210ms，分别对应8/12/14bit 测量。确切的时间随内部晶振速度，最多有15%变化。SHTxx 通过下拉DATA 至低电平并进入空闲模式，表示测量的结束。控制器在再次触发SCK 时钟前，必须等待这个“数据备妥”信号来读出数据。检测数据可以先被存储这样控制器可以继续执行其它任务在需要时再读出数据。接着传输2 个字节的测量数据和1 个字节的CRC 奇偶校验。uC 需要通过下拉DATA 为低电平，以确认每个字节。所有的数据从MSB 开始，右值有效（例如：对于12bit 数据，从第5 个SCK 时钟起算作MSB； 而对于 8bit 数据， 首字节则无意义）。用 CRC 数据的确认位，表明通讯结束。如果不使用CRC-8 校验，控制器可以在测量值LSB 后，通过保持确认位ack 高电平， 来中止通讯。在测量和通讯结束后，SHTxx 自动转入休眠模式。警告：为保证自身温升低于0.1，SHTxx 的激活时间不要超过15%（例如，对应12bit 精度测量，每秒最多进行3 次测量）。2.2.5 通讯复位时序如果与 SHTxx 通讯中断，下列信号时序可以复位串口：当DATA 保持高电平时，触发SCK 时钟9 次或更多。在下一次指令前，发送一个“传输启动”时序。这些时序只复位串口，状态寄存器内容仍然保留。图 4 通讯复位时序2.2.6 CRC-8 校验数字信号的整个传输过程由 8bit 校验来确保。任何错误数据将被检测到并清除。详情可参阅应用说明“CRC-8 校验”。图 6 测量时序概览 (TS = 启动传输)2.3 状态寄存器SHTxx 的某些高级功能可以通过状态寄存器实现。下面的章节概括介绍了这些功能。详情可参阅应用说明“状态寄存器”。图 7 状态寄存器读 图 8 状态寄存器写2.3.1 测量分辨率默认的测量分辨率分别为14bit（温度）、12bit（湿度），也可分别降至12bit 和8bit。通常在高速或超低功耗的应用中采用该功能。2.3.2 电量不足“电量不足”功能可监测到Vdd 电压低于2.47V 的状态。精度为0.05V。2.3.3 加热元件芯片上集成了一个可通断的加热元件。接通后，可将SHTxx 的温度提高大约5（9）。功耗增加8mA 5V。应用于：比较加热前后的温度和湿度值，可以综合验证两个传感器元件的性能。 在高湿 (95 %RH) 环境中，加热传感器可预防结露，同时缩短响应时间，提高精度。警告: 加热 SHTxx 后温度升高、相对湿度降低，较之加热前，示值略有差异。3 输出转换为物理量3.1 相对湿度为了补偿湿度传感器的非线性以获取准确数据，建议使用如下公式1修正读数：RHlinear = c1 +c2 SORH +c3 SORH2 表 6 湿度转换系数 表 7 温度补偿系数 湿度传感器对电压基本上没有依赖性。图 10 从 SORH 转换到相对湿度3.1.1 相对湿度对于温度依赖性的补偿由于实际温度与测试参考温度25 (77)的显著不同， 应考虑湿度传感器的温度修正系数：RHtrue = (TC - 25)(t1 +t2 SORH)+RHlinear3.2 温度由能隙材料PTAT (正比于绝对温度) 研发的温度传感器具有极好的线性。可用如下公式将数字输出转换为温度值：Temperatur