Starting at $1,669.00
  • Usually ships in 3-4 weeks



  • Small diameter sheath, 3.2mm (0.125 in)
  • Excellent stability
  • Includes ITS-90 coefficients
  • NVLAP-accredited calibrated from -328 to 932°F (–200 to 500°C), lab code 200706-0
  • 316 SST sheath material
  • Reduced response time without compromising precision
  • 4 seconds maximum time constant
  • Three sizes available:
    • 5618B-12; 305 mm L x 3.2 mm dia. (12 x 1/8 in)
    • 5618B-9; 229 mm L x 3.2 mm dia. (9 x 1/8 in)
    • 5618B-6; 152 mm L x 3.2 mm dia. (6 x 1/8 in)


The Fluke Calibration 5618B Small Diameter Industrial RTD (formerly Hart Scientific) is an excellent choice for secondary level performance with full ITS-90 calibration for critical temperature measurements. Featuring a 3.2 mm diameter (1/8 in) sheath, these industrial standards probes have reduced response time without compromising precision. This small diameter 5618B probe works well in many applications where immersion depth is limited. Larger diameter probes give more measurement error in short immersion depth applications because they conduct more heat between ambient and the sensor.

With each probe you will receive a full NVLAP-accredited calibration report. On the report you'll get the test data and the ITS-90 calibration coefficients that you can easily input into your Fluke Calibration thermometer. If you are using a 1521 Handheld Thermometer readout, we'll program the coefficients directly into your INFO-CON connector.

The 5618B is also a great probe to use for calibrating your Fluke Calibration 9132 or 9133 infrared calibrators. In fact, these IR black body heat sources were designed to be calibrated with this type of probe. Now you can calibrate these targets in your own lab!

For use from -328 to 932°F (–200 to 500°C) (the six-inch model goes to 572°F/300°C), you won't find a better industrial standard in this configuration than our 5618B. We recommend using the 5618B PRTs with the 1521, 1522, 1502A, 1529, or 1560 thermometer readouts.