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MAX31855
Cold-Junction Compensated
Thermocouple-to-Digital Converter
Detailed Description
The MAX31855 is a sophisticated thermocouple-to-
digital converter with a built-in 14-bit analog-to-digital
converter (ADC). The device also contains cold-junction
compensation sensing and correction, a digital control-
ler, an SPI-compatible interface, and associated control
logic. The device is designed to work in conjunction
with an external microcontroller ( F C) in thermostatic,
process-control, or monitoring applications. The device
is available in several versions, each optimized and
trimmed for a specific thermocouple type (K, J, N, T, S,
R, or E.). The thermocouple type is indicated in the suffix
of the part number (e.g., MAX31855K). See the Ordering
Information table for all options.
Temperature Conversion
The device includes signal-conditioning hardware to
convert the thermocouple’s signal into a voltage com-
patible with the input channels of the ADC. The T+ and
T- inputs connect to internal circuitry that reduces the
introduction of noise errors from the thermocouple wires.
Before converting the thermoelectric voltages into equiv-
alent temperature values, it is necessary to compensate
for the difference between the thermocouple cold-
junction side (device ambient temperature) and a 0 N C
virtual reference. For a K-type thermocouple, the volt-
age changes by about 41 F V/ N C, which approximates
the thermocouple characteristic with the following linear
equation:
V OUT = (41.276 F V/ N C) x (T R - T AMB )
where V OUT is the thermocouple output voltage ( F V), T R
is the temperature of the remote thermocouple junction
( N C), and T AMB is the temperature of the device ( N C).
Other thermocouple types use a similar straight-line
approximation but with different gain terms. Note that the
MAX31855 assumes a linear relationship between tem-
perature and voltage. Because all thermocouples exhibit
some level of nonlinearity, apply appropriate correction
to the device’s output data.
Cold-Junction Compensation
The function of the thermocouple is to sense a difference
in temperature between two ends of the thermocouple
wires. The thermocouple’s “hot” junction can be read
across the operating temperature range ( Table 1 ). The
reference junction, or “cold” end (which should be at
Table 1. Thermocouple Wire Connections and Nominal Sensitivities
COLD-JUNCTION
TYPE
K
J
N
S
T
E
R
T- WIRE
Alumel
Constantan
Nisil
Platinum
Constantan
Constantan
Platinum
T+ WIRE
Chromel
Iron
Nicrosil
Platinum/Rhodium
Copper
Chromel
Platinum/Rhodium
TEMP RANGE ( ° C)
-270 to +1372
-210 to +1200
-270 to + 1300
+50 to +1768
-270 to +400
-270 to +1000
-50 to +1768
SENSITIVITY (μV/ ° C)
41.276
(0 N C to +1000 N C)
57.953
(0 N C to +750 N C)
36.256
(0 N C to +1000 N C)
9.587
(0 N C to +1000 N C)
52.18
(0 N C to +400 N C)
76.373
(0 N C to +1000 N C)
10.506
(0 N C to +1000 N C)
SENSITIVITY (μV/ ° C)
(0 N C TO +70 N C)
40.73
52.136
27.171
6.181
41.56
44.123
6.158
Maxim Integrated
8
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相关代理商/技术参数
MAX31855JASA+ 功能描述:数据转换 IC - 多种 Thermocouple To Digital Converter RoHS:否 制造商:Texas Instruments 转换器数量:1 分辨率:8 bit 工作电源电压:2.7 V to 5.5 V 功耗: 工作温度范围:- 40 C to + 85 C 封装 / 箱体:MSOP-10 封装:Reel
MAX31855JASA+T 功能描述:数据转换 IC - 多种 Thermocouple To Digital Converter RoHS:否 制造商:Texas Instruments 转换器数量:1 分辨率:8 bit 工作电源电压:2.7 V to 5.5 V 功耗: 工作温度范围:- 40 C to + 85 C 封装 / 箱体:MSOP-10 封装:Reel
MAX31855KASA+ 功能描述:数据转换 IC - 多种 Thermocouple To Digital Converter RoHS:否 制造商:Texas Instruments 转换器数量:1 分辨率:8 bit 工作电源电压:2.7 V to 5.5 V 功耗: 工作温度范围:- 40 C to + 85 C 封装 / 箱体:MSOP-10 封装:Reel
MAX31855KASA+T 功能描述:数据转换 IC - 多种 Thermocouple To Digital Converter RoHS:否 制造商:Texas Instruments 转换器数量:1 分辨率:8 bit 工作电源电压:2.7 V to 5.5 V 功耗: 工作温度范围:- 40 C to + 85 C 封装 / 箱体:MSOP-10 封装:Reel
MAX31855NASA+ 功能描述:数据转换 IC - 多种 Thermocouple To Digital Converter RoHS:否 制造商:Texas Instruments 转换器数量:1 分辨率:8 bit 工作电源电压:2.7 V to 5.5 V 功耗: 工作温度范围:- 40 C to + 85 C 封装 / 箱体:MSOP-10 封装:Reel
MAX31855NASA+T 功能描述:数据转换 IC - 多种 Thermocouple To Digital Converter RoHS:否 制造商:Texas Instruments 转换器数量:1 分辨率:8 bit 工作电源电压:2.7 V to 5.5 V 功耗: 工作温度范围:- 40 C to + 85 C 封装 / 箱体:MSOP-10 封装:Reel
MAX31855PMB1# 功能描述:温度传感器模块 MAX31855 Peripheral Module RoHS:否 制造商:Maxim Integrated 产品:K-Type Thermocouples 温度范围:- 270 C to + 1800 C 准确性:+/- 2 C 分辨率:0.25 C 输出类型:Digital 接口类型:SPI 工作电源电压:3.3 V 工作电源电流:900 uA 最大工作温度:+ 125 C 尺寸:
MAX31855RASA+ 功能描述:数据转换 IC - 多种 Thermocouple To Digital Converter RoHS:否 制造商:Texas Instruments 转换器数量:1 分辨率:8 bit 工作电源电压:2.7 V to 5.5 V 功耗: 工作温度范围:- 40 C to + 85 C 封装 / 箱体:MSOP-10 封装:Reel