Three-wire connection to the RTD allows cancellation of the cable's resistance

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Other Materials from the Main Document

• Article «DIY RTD for a DMM»
• Figure 1. A bridge incorporating an RTD produces a voltage output related to the temperature, but usually with an offset 0 °C point
• Figure 2. Using matched current sources in the bridge gives a linear relationship between temperature and output, and helps us define a reference point of 0 °C. Choosing the currents carefully gives a bridge output of 1 mV / °C
• Figure 3. A practical circuit capable of delivering exactly 1 mV/°C
• Figure 4. Three-wire connection to the RTD allows cancellation of the cable's resistance
• Figure 5. A higher battery voltage allows the use of MOSFETs in the current sinks, while a lower current in the reference arm of the bridge saves some supply current