Fluke Calibration 5609-400-P Secondary PRT Probe, 100 Ohm, -200 to 670C, 6 x 400MM

If you want a very stable thermometer from –200 °C to 670 °C and are particular about the calibration, then look no further than the 5609 Secondary Reference PRT. Its short-term stability at the triple point of water is only ± 7 mK and its one-quarter inch (6.23mm) diameter lets you get accurate measurements in only 100 mm of immersion.