The first step in identifying an RTD is to find out how many lines it has (2, 3 or 4). Then you can connect the RTD to the multimeter. If it's a pt100, it should read between 107-110Ω at room temperature. But if it's a pt1000. You should get a reading of 1007 - 1100Ω. This confirms it's a Pt1000. PLEASE NOTE: These readings are standard for new RTD sensors. If the sensor is damaged or used continuously. The readings may vary.