MAX31855NASA-T 데이터 시트보기 (PDF) - Maxim Integrated
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MAX31855NASA-T Datasheet PDF : 13 Pages
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MAX31855
Cold-Junction Compensated
Thermocouple-to-Digital Converter
Applications Information
Noise Considerations
Because of the small signal levels involved, thermocou-
ple temperature measurement is susceptible to power-
supply coupled noise. The effects of power-supply noise
can be minimized by placing a 0.1FF ceramic bypass
capacitor close to the VCC pin of the device and to GND.
The input amplifier is a low-noise amplifier designed to
enable high-precision input sensing. Keep the thermo-
couple and connecting wires away from electrical noise
sources.
Thermal Considerations
Self-heating degrades the device’s temperature measure-
ment accuracy in some applications. The magnitude of the
temperature errors depends on the thermal conductivity
of the device package, the mounting technique, and the
effects of airflow. Use a large ground plane to improve the
device’s temperature measurement accuracy.
The thermocouple system’s accuracy can also be
improved by following these precautions:
• Use the largest wire possible that does not shunt heat
away from the measurement area.
• If a small wire is required, use it only in the region
of the measurement, and use extension wire for the
region with no temperature gradient.
• Avoid mechanical stress and vibration, which could
strain the wires.
• When using long thermocouple wires, use a twisted
pair extension wire.
• Avoid steep temperature gradients.
• Try to use the thermocouple wire well within its tem-
perature rating.
• Use the proper sheathing material in hostile environ-
ments to protect the thermocouple wire.
• Use extension wire only at low temperatures and only
in regions of small gradients.
• Keep an event log and a continuous record of thermo-
couple resistance.
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