A Regional Comparison of Calibration Results for Type K Thermocouple Wire from (100 to 1,100) °C

Abstract

Under the auspices of the Inter-American Metrology System (SIM), the National Institute of Standards and Technology (NIST) initiated a regional comparison for type K thermocouples from (100 to 1,100) • C with 11 participating countries. The use of type K material above approximately 200 • C is considered destructive. Therefore, each participating laboratory was sent new, unused wire from a lot of material characterized by NIST. The uniformity of the lot was remarkable, especially at temperatures above 500 • C; the standard deviation of the thermocouple emf values of multiple cuts tested at NIST was 2.7 µV or less over the full temperature range. The high uniformity eliminated any need to correct for variations of the transfer standard among the laboratories, greatly simplifying the analysis. The level of agreement among the laboratories' results was quite good. Even though test procedures and equipment varied significantly among the participants, the standard deviation of all emf values at each test temperature was less than the equivalent of 0.20 • C at 200 • C and below, and less than 0.60 • C from (400 to 1,100) • C. Of the 380 total bilateral combinations of the

Peak Stir Zone Temperatures during Friction Stir Processing

“…For sheathed and grounded type-K thermocouples embedded in a solid plate, an effective time constant can be estimated to be 0.02 to 0.06 seconds [29] and repeatability is estimated to be better than 1°C. [30] Thermocouple output was recorded at 10 points per second using a computer-based data acquisition system. Finally, the thermocouple sheaths were bent around a radius and press fitted into a channel machined into the bottom of the plate; the channel edges were lightly peened to lock the thermocouples in place.…”

Effect of FSP process parameters with air blowing on microstructure and hardness of NiAl Bronze alloy

“…The equilibrium of forces and moments, traversing of the tool, and localized plastic deformation induced by tool rotation result in rapid transients and steep gradients in the SZ strain, strain rate, and temperature [19]. At high transient temperatures, the uncertainty within K-type TCs' readings may occur as mentioned in previous literature [23,24]. The mentioned uncertainty may be attributed to: (1) thermal inertia (2) electrical amplifiers (3) analogto-digital converters (4) surrounding temperature compensation (5) presence of electrical/magnetic fields, or (6) random ground currents [24].…”

Thermocouple homogeneity scanning

“…a convenient measure of the width of the kernel is the standard deviation, σ x . The spatial frequency response is given by the Fourier transform of (8), which is a low-pass response that is also Gaussian in shape:…”

“…Certainly, for reference thermocouples complying with the noble-metal letter-designated type definitions (types R, S and B) and the pure-element thermocouples (Au/Pt, Pt/Pd), for which the temperature-induced inhomogeneity effects are smallest and most reproducible, some assessment can be made relatively easily [6]. Uncertainty calculations presented in comparisons suggest it is common to apply a value based on a type B assessment of published data from other studies [7], or data from a representative sample of similar thermocouples [8], rather than data from the device under test (DUT). In many cases it appears likely that inhomogeneity is simply not included in the uncertainty assessment [8,9].…”

“…Uncertainty calculations presented in comparisons suggest it is common to apply a value based on a type B assessment of published data from other studies [7], or data from a representative sample of similar thermocouples [8], rather than data from the device under test (DUT). In many cases it appears likely that inhomogeneity is simply not included in the uncertainty assessment [8,9]. Reed [10] noted that it is common for calibration reports to be issued for reference thermocouples that are severely inhomogeneous with no uncertainty component accounting for the inhomogeneities.…”