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| 型号： | LMP90079MH/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 模拟信号调理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PDSO28 |
| 封装： | LEAD FREE, PLASTIC, MO-153, TSSOP-28 |
| 文件页数： | 42/62页 |
| 文件大小： | 1721K |
| 代理商： | LMP90079MH/NOPB |
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17.6.2 Thermocouple and IC Analog Temperature
30169799
FIGURE 39. Thermocouple with CJC
The LMP900xx is also ideal for thermocouple temperature
applications. Thermocouples have several advantages that
make them popular in many industrial and medical applica-
tions. Compare to RTDs, thermistors, and IC sensors, ther-
mocouples are the most rugged, least expensive, and can
operate over the largest temperature range.
A thermocouple is a sensor whose junction generates a dif-
ferential voltage, VIN, that is relative to the temperature dif-
ference (Thot – Tcold). Thot is also known as the measuring
junction or “hot” junction, which is placed at the measured
environment. Tcold is also known as the reference or “cold”
junction, which is placed at the measuring system environ-
ment.
Because a thermocouple can only measure a temperature
difference, it does not have the ability to measure absolute
temperature. To determine the absolute temperature of the
measured environment (Thot), a technique known as cold
junction compensation (CJC) must be used.
In a CJC technique, the “cold” junction temperature, Tcold, is
sensed by using an IC temperature sensor, such as the
LM94022. The temperature sensor should be placed within
close proximity of the reference junction and should have an
isothermal connection to the board to minimize any potential
temperature gradients.
Once Tcold is obtained, use a standard thermocouple look-
up-table to find its equivalent voltage. Next, measure the
differential thermocouple voltage and add the equivalent cold
junction voltage. Lastly, convert the resulting voltage to tem-
perature using a standard thermocouple look-up-table.
For example, assume Tcold = 20°C. The equivalent voltage
from a type K thermocouple look-up-table is 0.798 mV. Next,
add the measured differential thermocouple voltage to the
Tcold equivalent voltage. For example, if the thermocouple
voltage is 4.096 mV, the total would be 0.798 mV + 4.096 mV
= 4.894 mV. Referring to the type K thermocouple table gives
a temperature of 119.37°C for 4.894 mV.
47
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LMP90080/LMP90079/LMP90078/LMP90077
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LMP90079MHX/NOPB | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| LMP90080 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Sensor AFE System: Multi-Channel, Low-Power 16-Bit |
| LMP90080MH/NOPB | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| LMP90080MHE/NOPB | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| LMP90080MHX/NOPB | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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