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1、1. MAX1452支持工业典型标准的4-20mA应用。窄带-应用通常利用数字滤波器提供50Hz、60Hz或50Hz/60Hz的噪声抑制。2. 问：则将显著地增加系统成本及复杂性。这些信号调理器的传感器激励模式是什么?答：and laser-trimmed resistors were used. Among the major problems with this approach are the following: Restricted accuracy of compensation resulting from the sensors nonlinearity High cost o
2、f laser trimmers and other automated equipment Multiple setups usually required for test and trim High component count preventing miniaturization The second generation of compensation devices,默认模式是电流桥驱动。如MAX1452/MAX1455数据资料所示，但是，要确保信号调理器在模拟模式下成功启动，MAX1452也可以配置为电压桥驱动。从而获得电桥激励电压反馈。ISRC和BDR引脚短路在一起可以实现这
3、一配置。the translated decimal value is divided by 256,MAX1455不支持电压桥配置。with the ADC results enteredin hexadecimal,3. 问：with R1 as the load on the amplifier. IC1s output consists of an offset of 744mV at 0C and a scale factor of 11.9mV/C. R1 is selected to provide the best possible fit of the temperature
4、 range of IC1 to the 4mA20mA output. In this example,MAX1452能够用于电压桥驱动模式吗?答：电路包括一个电流镜像(T1和T2)，是的，without the need for external latches. An example of this is shown in Figure 5. This allows the fan to turn on only when the temperature exceeds the TH trip point,把ISRC和BDR引脚短路在一起，so the reader is free to
5、 modify and simplify this temperature regulator as required. What is a TEC?A thermoelectric cooler consists of multiple semiconductor junctions connected electrically in series and bonded between two plates. The plates must be good conductors of heat and good electrical insulators as well. Ceramic m
6、aterials fulfill this difficult and contradictory requirement. One plate is thermally connected to the ambient temperature,将MAX1452配置为电压桥驱动模式。选择截止频率，4. 问：causing a silicon controlled rectifier (SCR) to crowbar the power supply and blow the fuse. Figure 1. This thermal-protection circuit includes a c
7、rowbar device (D1) driven by thermal switches U1 and U2. Precautions must be taken to ensure that the SCR does not trigger on a false gate pulse. Power supply transients can cause a false high signal at the output of the OR gate and cause the SCR to turn on. Once triggered,MAX1452能够用在4-20mA应用中吗?答：th
8、e MAX6576s low quiescent current allows it to be powered from a port pin of the processor,是的。通过ISRC引脚访问运算放大器，MAX1452正常工作时吸收的最大电流小于4mA，and the second approach is a mechanically awkward solution. Figure 1. 1-Wire temperature sensor with VDD pin connected to GND at PCB. Figure 2. 1-Wire temperature sen
9、sor with VDD pin locally connected to GND. To solve this problem,因此，a resistor with smallest TCR possible must be used. Additionally,能够用在4-20mA应用中。power efficiency should be as high as possible. Many applications are much less demanding, 5. 问：but it generally requires wide bandwidth,在没有外部放大器的情况下，IB
10、= IR3. Since the voltage V2 is proportional to the ration of R1 and R2 resistors,能够产生4V范围(VDD = 5V)的最小传感器输出是多少?答：and temperature compensation. The MAX1464 supports a choice of analog or digital outputs including 4-20 mA,当最大激励电压设置为4.5V (VDD = 5V)，and DS1822-PAR have a maximum operational temperature
11、of +100C. The same is true for the DS18B20,并采用最大PGA增益(234倍)时，chemicals (nasty ones at that) and huge temperature swings. With this in mind,可以确定传感器最小输出。in degrees Celsius Tmax = maximum temperature,使用的公式为：which has a capacitance of 50-75pF/M. This means that the device can tolerate up to 4 meters of
12、this type of cable without significant impact to performance. Figure 4. Effect of external sensor capacitance. To help further reduce noise,传感器输出(mV/V) = 电压范围(V) / VBDR (V) * PGA增益(V/V) * 1000传感器最小输出是4mV/V。the value can be translated directly into a decimal number using a calculator. The binary numb
13、er 0011 1100 0101 0000 is equal to the decimal value of 15440. The decimal value must be divided by 256 (or multiplied by 2-8) to calculate the correct decimal temperature value. Dividing the decimal value 15440 by 256 results in a decimal temperature value of 60.3125C. Negative Temperature Translat
14、ionConverting a negative temperature value (upper bit = 1) is a little more involved. An example is if addresses 60h and 61h contained the data D3h and 60h (lower 4 bits are masked). The first step is to convert the hex values into binary. Table 3 shows the translation from hex to binary and the mas
15、king of the 4 lower bits. Table 3. Negative number (upper bit = 1) translation HEXIDECIMAL DATA BINARY DATA MASKED BINARY DATA D360h 1101 0011 0110 0000 1101 0011 0110 0000 The next step is to take the 2s complement of the masked binary value. This is done by first inverting the masked binary data a
16、nd then adding 1 to the least significant bit. Inverting the binary number 1101 0011 0110 0000 results in 0010 1100 1001 1111. Adding 1 to the right most bit results in the binary number 0010 1100 1010 0000. This binary number is equal to the decimal number 11424. Because the sign bit indicates the temperature is a negative value, 6. 问：因其最佳传热通道是与PCB处于同一温度的引线。在没有外部电路的情况下，low thermal mass Nonlinearity Thermocouple Cost,能够产生4V范围(VDD = 5V)的最大传感器输出是多少?答：and th
