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MAX31865 RTD-to-Digital Converter Slide 7
The ADC solution to digitizing RTDs can easily detect sensor faults in some cases, while this is more challenging with others. A shorted RTD would report a very low or 0 RTD voltage. An open RTD would report a very low reference voltage, given that no current would be flowing through Rref. However, some faults may appear as valid data when measured by the ADC. For example, a short circuit in the lower sense cable to ground would effectively bypass the current sink, introducing an error in the measurement due to resistance in the cables. The resulting measurement by the ADC would be in the valid range and would therefore not be detected by the system. Determining faults simply by analyzing ADC measurement may not be comprehensive.
PTM Published on: 2013-01-24