5699 High-Temperature Metal-Sheath SPRT




Product Description

5699 High-Temperature Metal-Sheath SPRT

Designed and manufactured by our primary standards metrologists, the strain-free sensing element in the 5699 meets all ITS-90 requirements for SPRTs and minimizes long-term drift.

After one year of regular usage, drift is less than 0.008 °C (< 0.003 °C is typical). Even lower drift rates are possible depending on care and handling. A fifth wire for grounding is added to the four-wire sensor to help reduce electrical noise, particularly for AC measurements. Finally, you can get an improved version of an old industry-standard Inconel-sheathed SPRT.

The 5699 is constructed with a 0.219-inch-diameter Inconel sheath for high durability and fast response times. Inside the sheath, the sensing element is protected by a thin platinum housing that shields the sensor from contamination from free-floating metal ions found within metal environments at high temperatures. Reduced contamination means a low drift rate—even after hours of use in metal-block furnaces at high temperatures.

If you choose not to calibrate the 5699 yourself, a wide variety of options are available from Fluke Calibration’s own primary standards laboratory, including fixed-point calibrations covering any range between –200 °C and 661 °C.

At Fluke Calibration, we use SPRTs every day. We design them, build them, calibrate them, use them as standards, and know what it takes to make a reliably performing instrument. Why buy from anyone else?


Affordable working standard SPRT

  • Range to aluminum point (660 °C )
  • Inconel™ and platinum sheaths guard against contamination
  • Less than 8 mK/year drift
  • Many calibration options available including by fixed point
  • Fifth wire provides shield ground

SPRTs designed by Fluke Calibration are known for their outstanding reliability and minimal long-term drift. They have been calibrated by national (and other primary) laboratories and proven repeatedly to outperform competitive models. Now Fluke Calibration’s 5699 Extended Range Metal-Sheath SPRT combines all the advantages of a Fluke Calibration-designed sensor with the protective sheathing materials that allow your SPRT to be used in virtually any furnace or bath with temperatures as high as 670 °C.


Temperature Range –200 °C to 670 °C
Nominal RTPW 25.5Ω (± 0.5Ω)
Current 1 mA
Resistance Ratio W(302.9146 K) ≥ 1.11807
W(234.3156 K) ≤ 0.844235
Sensitivity 0.1 Ω/ °C
Drift Rate < 0.008 °C/year
(< 0.003 °C/year typical)
Repeatability < 1 mK
Self-heating at TPW < 0.001 °C under 1 mA current
Reproducibility ± 0.001 °C or better
RTPW Drift After Thermal Cycling < 0.001 °C
Diameter of Pt Sensor Wire 0.07 mm
(0.003 in)
Lead Wires Four sensor wires plus grounding wire
Protective Sheath Inconel
Diameter 5.56 mm ± 0.13 mm (0.219 in ± 0.005 in)
Length 482 mm (19 in)
Insulation Resistance > 100 MΩ at 661 °C
> 1000 MΩ at 20 °C

Models and Accessories

Model Name Description
5699-S Extended Range Metal-Sheath SPRT with Maple carrying case

Knowledge and Information

Product Manuals
application/pdf icon 5680/5682/5699 Metal Sheath Standard Platinum Resistance Thermometer User’s Guide (142.62 KB)
Application Notes
application/pdf icon Establishment of a Primary Temperature Standards Laboratory (3.21 MB)
application/pdf icon Establishment of a Secondary Temperature Calibration Laboratory (3.09 MB)
application/pdf icon Improving Productivity in a Temperature Calibration Laboratory (1.09 MB)
application/pdf icon Temperature Calibration Equipment: A Technician’s Guide (1.62 MB)
application/pdf icon Why Use a Triple Point of Water? (1.19 MB)
Papers / Articles
application/pdf icon A Monte Carlo Analysis of the Effects of Covariance on Propagated Uncertainties (156.57 KB)
application/pdf icon Achieving 0.25 mK Uncertainty with an Integrated-Circuit Resistance Thermometer Readout (78.91 KB)
application/pdf icon Demonstrating Competency and Equivalency of Two Commercial SPRT Calibration Facilities (365.33 KB)
application/pdf icon Experimental Study of Different Filling Gases on the Stability of Metal-Sheathed Standard Platinum Resistance Thermometers (380.62 KB)
application/pdf icon Fixed Points for Secondary Level and Industrial Calibration (496.68 KB)
application/pdf icon How Does Temperature Non-uniformity of an Annealing Furnace Affect SPRT Stability? (88.14 KB)
application/pdf icon Improving the Stability of Standard Platinum Resistance Thermometers (207.37 KB)
application/pdf icon Long-Term Resistance and Ratio Stability of SPRTS, Comparing Metal Sheaths vs. Fused Silica Sheaths (112.93 KB)
application/pdf icon Producing the Highest Accuracy from SPRTs (289.83 KB)
application/pdf icon Using a Mini Triple Point of Water System to Improve Reliability in a Temperature Calibration Laboratory (177.86 KB)
Why Use an Annealing Furnace?
On-Demand Webinars
Overcoming Drift: Tips to Maintaining Your PRTs

About us

บริษัท เมสเชอร์เมนท์เอเชีย จำกัด
Measurementasia Co.,Ltd.

99 Moo. 3, Khlong 5, Khlong Luang,
Pathumthani 12120



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