Digital Thermometer Calibration -196°C to +200°C: ISO 17025 Operating Procedure (FD X 07-011 Guide)

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The calibration of a thermometer covering the range -196°C to +200°C involves two distinct physical domains: the cryogenic domain and the high temperature domain, in accordance with Guide FD X 07-011.

1. Reference Equipment by Range

Range Reference Equipment Calibration Medium
-196°C to -100°C SPRT Thermometer Controlled liquid nitrogen bath
-100°C to 0°C Pt100 Thermometer Alcohol cryostatic bath
0°C to +100°C Pt100 Thermometer Water-controlled bath
+100°C to +200°C Pt100 Thermometer Silicone oil-controlled bath

2. Control Points | Variable MPE

Nominal Point Average Deviation MPE Status
-196.0°C -195.67 +0.33 ±0.5°C ✅ CONFORMING
-100.0°C -99.73 +0.27 ±0.5°C ✅ CONFORMING
-10.0°C -9.77 +0.23 ±0.5°C ✅ CONFORMING
0.0°C +0.23 +0.23 ±0.5°C ✅ CONFORMING
+50.0°C +50.37 +0.37 ±0.5°C ✅ CONFORMING
+100.0°C +100.57 +0.57 ±1.0°C ✅ CONFORMING
+200.0°C +200.77 +0.77 ±1.0°C ✅ CONFORMING

3. Thermal Variation Correction

A. Spatial inhomogeneity of the bath (u_homo)

u_homo = ΔT_spatial / (2√3) = 0.1 / (2√3) = 0.029°C

B. Temporal instability of the bath (u_stab)

u_stab = ΔT_temporal / (2√3) = 0.05 / (2√3) = 0.014°C

4. Uncertainty Budget

Source Value (k=1)
u_homo 0.029°C
u_stab 0.014°C
u_ref 0.050°C
u_res 0.029°C
u_drift 0.020°C
Expanded U (k=2) 0.14°C

ILAC-G8 at +200°C point: |0.77| + 0.14 = 0.91°C < MPE 1.0°C → ✅ CONFORMING

5. ISO 17025 Compliance

  • Traceability: Traceability chain to LNE
  • §7.6: Expanded uncertainty U declared on the PV for each range
  • §7.8.6: ILAC-G8 rule applied point by point
  • Periodicity: 12 months — extendable to 24 months via OIML D10

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