Probe thermometer 5686-B

platinum resistiveRTDwithout display

Product summary
The Fluke 5686‑B glass‑capsule Standard Platinum Resistance Thermometer (SPRT) is a primary‑standard device for converting temperature to resistance with ITS‑90 compliance. It operates from −260 °C (13 K) to 232 °C (505 K). The miniature glass capsule enables full immersion, lowers heat flow and suits confined or total‑immersion calibrations. The sensing element is high‑purity platinum wire hand‑wound on a fused‑silica cross frame; the capsule is pressure‑sealed with high‑purity helium to preserve long‑term stability.

Key features

• Miniature glass‑capsule SPRT optimized for metrology tasks requiring short, fully immersible probes.
• Wide temperature range: −260 °C to 232 °C with typical stability of 0.001 °C over 100 °C.
• Compact size (5.8 mm × 56 mm) for use in vessels, cryogenic setups and confined spaces.
• True SPRT construction: high‑purity platinum wire, hand‑wound on a strain‑free fused‑silica frame.

Detailed features

• ITS‑90 compliance – Designed to meet the International Temperature Scale of 1990 with specified resistance‑ratio limits:
  • W(302.9146 K) ≥ 1.11807
  • W(234.3156 K) ≤ 0.844235
• Exceptional temperature coverage – Operates from cryogenic temperatures (13 K / −260 °C) up to 232 °C (505 K).
• Compact, fully immersible design – 5.8 mm diameter × 56 mm length; minimizes heat flow and enables total immersion in fixed‑point cells and calibration baths.
• Fixed‑point calibration ready – Suitable for fixed‑point calibrations from −200 °C to 232 °C.
• Low self‑heating and high reproducibility – Self‑heating at TPW < 0.002 °C (1 mA); reproducibility ±0.001 °C or better.

Specifications

• Model: 5686‑B
• Temperature range: −260 °C to 232 °C (13 K to 505 K)
• Nominal R_TPW: 25.5 Ω
• Resistance ratio: W(302.9146 K) ≥ 1.11807; W(234.3156 K) ≤ 0.844235
• Drift rate: < 0.005 °C per year (entire range)
• Self‑heating at TPW: < 0.002 °C (1 mA)
• Reproducibility: ±0.001 °C or better
• R_TPW drift after thermal cycling: < 0.001 °C
• Filling gas: helium
• Lead wires: four platinum wires, 30 mm long
• Size: 5.8 mm dia. × 56 mm length

Applications and advantages

• Designed for primary‑standard calibration work including cryogenics and immersion fixed‑point cells.
• Compact alternative to long‑stem SPRTs where full immersion and limited space are required.
• Engineered for low self‑heating, minimal drift and proven reproducibility to support metrology laboratories.