Fluke RTD Temperature Probe 720RTD The Fluke-720RTD temperature probe is for use with Fluke 721 precision pressure calibrators and Fluke 719Pro electric pressure calibrators. The 720RTD has a 10 inch (254mm) insertion depth with inch (6.3mm) diameter stainless steel sheath. If a Fluke 721 precision pressure calibrator is used with the Fluke 720RTD probe then it is not necessary to set the probe type. The user simply connects probe to calibrator and configures the display to read Temperature. The display shows 'OL' when the measured temperature is outside the nominal measurement range of the RTD function (below -40°C or above 150°C).