EVAL-CN0337-PMDZ: 12-Bit, 300 kSPS, Isolated RTD Temperature Measurement

The circuit on EVAL-CN0337-PMDZ is a completely isolated 12-bit, 300 kSPS RTD temperature measuring system that uses only three active devices. The system processes the output of a Pt100 RTD and includes a circuit for lead-wire compensation using a standard 3-wire connection. The circuit operates on a single 3.3 V supply. The total error after room temperature calibration is less than ±0.24% FSR for a ±10°C change in temperature, making it ideal for a wide variety of industrial temperature measurements.

Both data and power are isolated, thereby making the circuit robust to high voltages and also ground-loop interference often encountered in harsh industrial environments.

The input stage of the circuit is an RTD signal conditioning circuit using a compensated 3-wire connection to the RTD. The circuit translates the RTD input resistance range (100 Ω to 212.05 Ω for a 0°C to 300°C temperature range) into voltage levels compatible with the input range of the ADC (0 V to 2.5 V).