PROCESS TEMPERATURE TRANSMITTER WITH IMPROVED TEMPERATURE CALCULATION

摘要

[0023] In a process temperature transmitter (12), a method (100) for providing a process temperature output is described. The method (100) includes providing a measurement current through a circuit including a reference resistor (34) and a resistance temperature device (RTD) (32). A first voltage across the reference resistor is measured (102) while the measurement current flows through it. A first voltage across the RTD (32) is also measured (104) while the measurement current flows through it. A first resistance of the RTD (32) is calculated based on the measured voltage across the reference resistor (34) and the measured first voltage. A first process temperature output is provided based on the first resistance of the RTD (32). A second voltage is subsequently measured across the RTD (32) while a measurement current flows through it. A second voltage across the reference resistor (34) is then estimated based on the measured second voltage across the RTD (32) and the measured first voltage across the reference resistor (34). A second resistance across the RTD (32) is calculated based on the measured second voltage and the estimated second voltage. A second process temperature output is provided based on the second resistance.