温度传感器中英文对照外文翻译文献.docx

1、温度传感器中英文对照外文翻译文献 中英文资料外文翻译文献原文：Temperature Sensor ICs Simplify DesignsWhen you set out to select a temperature sensor, you are no longer limited to either an analog output or a digital output device. There is now a broad selection of sensor types, one of which should match your systems needs. Until

2、recently, all the temperature sensors on the market provided analog outputs. Thermistors, RTDs, and thermocouples were followed by another analog-output device, the silicon temperature sensor. In most applications, unfortunately, these analog-output devices require a comparator, an ADC, or an amplif

3、ier at their output to make them useful. Thus, when higher levels of integration became feasible, temperature sensors with digital interfaces became available. These ICs are sold in a variety of forms, from simple devices that signal when a specific temperature has been exceeded to those that report

4、 both remote and local temperatures while providing warnings at programmed temperature settings. The choice now isnt simply between analog-output and digital-output sensors; there is a broad range of sensor types from which to choose. Classes of Temperature SensorsFour temperature-sensor types are i

5、llustrated in Figure 1. An ideal analog sensor provides an output voltage that is a perfectly linear function of temperature (A). In the digital I/O class of sensor (B), temperature data in the form of multiple 1s and 0s are passed to the microcontroller, often via a serial bus. Along the same bus,

6、data are sent to the temperature sensor from the microcontroller, usually to set the temperature limit at which the alert pins digital output will trip. Alert interrupts the microcontroller when the temperature limit has been exceeded. This type of device can also provide fan control. Figure 1. Sens

7、or and IC manufacturers currently offer four classes of temperature sensors. Analog-plus sensors (C) are available with various types of digital outputs. The VOUT versus temperature curve is for an IC whose digital output switches when a specific temperature has been exceeded. In this case, the plus

8、 added to the analog temperature sensor is nothing more than a comparator and a voltage reference. Other types of plus parts ship temperature data in the form of the delay time after the part has been strobed, or in the form of the frequency or the period of a square wave, which will be discussed la

9、ter. The system monitor (D) is the most complex IC of the four. In addition to the functions provided by the digital I/O type, this type of device commonly monitors the system supply voltages, providing an alarm when voltages rise above or sink below limits set via the I/O bus. Fan monitoring and/or

10、 control is sometimes included in this type of IC. In some cases, this class of device is used to determine whether or not a fan is working. More complex versions control the fan as a function of one or more measured temperatures. The system monitor sensor is not discussed here but is briefly mentio

11、ned to give a complete picture of the types of temperature sensors available. Analog-Output Temperature SensorsThermistors and silicon temperature sensors are widely used forms of analog-output temperature sensors. Figure 2 clearly shows that when a linear relationship between voltage and temperatur

12、e is needed, a silicon temperature sensor is a far better choice than a thermistor. Over a narrow temperature range, however, thermistors can provide reasonable linearity and good sensitivity. Many circuits originally constructed with thermistors have over time been updated using silicon temperature

13、 sensors. Figure 2. The linearity of thermistors and silicon temperature sensors, two popular analog-output temperature detectors, is contrasted sharply. Silicon temperature sensors come with different output scales and offsets. Some, for example, are available with output transfer functions that ar

14、e proportional to K, others to C or F. Some of the C parts provide an offset so that negative temperatures can be monitored using a single-ended supply. In most applications, the output of these devices is fed into a comparator or an A/D converter to convert the temperature data into a digital forma

15、t. Despite the need for these additional devices, thermistors and silicon temperature sensors continue to enjoy popularity due to low cost and convenience of use in many situations. Digital I/O Temperature SensorsAbout five years ago, a new type of temperature sensor was introduced. These devices in

16、clude a digital interface that permits communication with a microcontroller. The interface is usually an IC or SMBus serial bus, but other serial interfaces such as SPI are common. In addition to reporting temperature readings to the microcontroller, the interface also receives instructions from the

17、 microcontroller. Those instructions are often temperature limits, which, if exceeded, activate a digital signal on the temperature sensor IC that interrupts the microcontroller. The microcontroller is then able to adjust fan speed or back off the speed of a microprocessor, for example, to keep temp

18、erature under control. This type of device is available with a wide variety of features, among them, remote temperature sensing. To enable remote sensing, most high-performance CPUs include an on-chip transistor that provides a voltage analog of the temperature. (Only one of the transistors two p-n

19、junctions is used.) Figure 3 shows a remote CPU being monitored using this technique. Other applications utilize a discrete transistor to perform the same function. Figure 3. A user-programmable temperature sensor monitors the temperature of a remote CPUs on-chip p-n junction. Another important feat

20、ure found on some of these types of sensors (including the sensor shown in Figure 3) is the ability to interrupt a microcontroller when the measured temperature falls outside a range bounded by high and low limits. On other sensors, an interrupt is generated when the measured temperature exceeds eit

21、her a high or a low temperature threshold (i.e., not both). For the sensor in Figure 3, those limits are transmitted to the temperature sensor via the SMBus interface. If the temperature moves above or below the circumscribed range, the alert signal interrupts the processor. Pictured in Figure 4 is

22、a similar device. Instead of monitoring one p-n junction, however, it monitors four junctions and its own internal temperature. Because Maxims MAX1668 consumes a small amount of power, its internal temperature is close to the ambient temperature. Measuring the ambient temperature gives an indication

23、 as to whether or not the system fan is operating properly.Figure 4. A user-programmable temperature sensor monitors its own local temperature and the temperatures of four remote p-n junctions. Controlling a fan while monitoring remote temperature is the chief function of the IC shown in Figure 5. U

24、sers of this part can choose between two different modes of fan control. In the PWM mode, the microcontroller controls the fan speed as a function of the measured temperature by changing the duty cycle of the signal sent to the fan. This permits the power consumption to be far less than that of the

25、linear mode of control that this part also provides. Because some fans emit an audible sound at the frequency of the PWM signal controlling it, the linear mode can be advantageous, but at the price of higher power consumption and additional circuitry. The added power consumption is a small fraction

26、of the power consumed by the entire system, though.Figure 5. A fan controller/temperature sensor IC uses either a PWM- or linear-mode control scheme. This IC provides the alert signal that interrupts the microcontroller when the temperature violates specified limits. A safety feature in the form of

27、the signal called overt (an abbreviated version of over temperature) is also provided. If the microcontroller or the software were to lock up while temperature is rising to a dangerous level, the alert signal would no longer be useful. However, overt, which goes active once the temperature rises abo

28、ve a level set via the SMBus, is typically used to control circuitry without the aid of the microcontroller. Thus, in this high-temperature scenario with the microcontroller not functioning, overt could be used to shut down the system power supplies directly, without the microcontroller, and prevent

29、 a potentially catastrophic failure. This digital I/O class of devices finds widespread use in servers, battery packs, and hard-disk drives. Temperature is monitored in numerous locations to increase a servers reliability: at the motherboard (which is essentially the ambient temperature inside the c

30、hassis), inside the CPU die, and at other heat-generating components such as graphics accelerators and hard-disk drives. Battery packs incorporate temperature sensors for safety reasons and to optimize charging profiles, which maximizes battery life. There are two good reasons for monitoring the tem

31、perature of a hard-disk drive, which depends primarily on the speed of the spindle motor and the ambient temperature: The read errors in a drive increase at temperature extremes, and a hard disks MTBF is improved significantly through temperature control. By measuring the temperature within the syst

32、em, you can control motor speed to optimize reliability and performance. The drive can also be shut down. In high-end systems, alerts can be generated for the system administrator to indicate temperature extremes or situations where data loss is possible. Analog-Plus Temperature Sensors Analog-plus sensors are generally suited to simpler measurement applications. These ICs generate a logic output derived from the measured temperature and are distinguished from digital I/O sensors primarily because they output data on a single line, as opposed to a serial bus.