High-temperature calibration bath ISOTOWER

for temperature sensorshigh-precisionportable

Overview
The ISOTOWER series are fixed-point assemblies integrated into a maintenance system based on a heat-pipe fluid and fitted with an immersion compensator (patented). The cell is integrated and protected; no handling of the cell is required. ISOTOWER units are available for the following EIT-90 fixed points: Indium, Tin, Zinc and Aluminium.

Available fixed points

• Indium
• Tin
• Zinc
• Aluminium

Principle and application
Each ISOTOWER combines a fixed-point cell with a heat-pipe (siphon) maintenance furnace to provide stable conditions for calibrating reference thermometers. Primary laboratories use large-format fixed-point cells inserted into deep heat-pipe furnaces to eliminate temperature gradients, a combination that yields very low uncertainties. Calibration accuracy depends directly on immersion depth. Above the heat-pipe well containing the cell, a heating block compensates for thermal losses due to thermometer immersion depth.

Plateau duration
Plateau durations of 24 hours or more are readily achieved; the datasheet specifies a typical plateau duration of 30 hours, providing an extended working window for full-day calibrations.

Benefits of ISOTOWER versus conventional system (quartz cell + maintenance furnace)
Quartz cell + maintenance furnace

• Fragile and high risk of breakage
• Difficult and costly to transport
• Cell is certified separately from the furnace; conduction through the sensor body is unknown
• Requires careful handling

ISOTOWER

• No glass or quartz used — increased robustness
• Easier to transport
• All-in-one system: known immersion characteristics
• Simple and secure handling

Table — Models and main characteristics
Models: 490 · 491 · 492 · 493
Fixed point: Indium · Tin · Zinc · Aluminium
Temperature (EIT-90): 156.5985°C · 231.928°C · 419.527°C · 660.323°C
Metal purity: 6N for all models
Plateau duration: 30 hours (typical value)
UKAS uncertainty (premium): 0.7 mK · 0.8 mK · 1 mK · 2 mK
UKAS uncertainty (standard): 2 mK · 2 mK · 2 mK · 6 mK
Heating time: 2 hours (per model)
Inner well diameter: 8 mm (typ.)
Immersion depth: 290 mm (typ.)
Metal column height: 180 mm (typ.)

Additional information
ISOTOWER units comply with stringent specifications (CCT/2000/13). The assembly is simple to set up, robust and easily transportable; the cell is integrated and protected.

Technical specifications

• Available models: 490 (Isotower Indium), 491 (Isotower Tin), 492 (Isotower Zinc), 493 (Isotower Aluminium)
• Temperatures (EIT-90): Indium 156.5985°C ; Tin 231.928°C ; Zinc 419.527°C ; Aluminium 660.323°C
• Metal purity: 6N for all models
• Plateau duration: 30 hours (typical)
• UKAS uncertainty (premium): 0.7 mK (Indium) ; 0.8 mK (Tin) ; 1 mK (Zinc) ; 2 mK (Aluminium)
• UKAS uncertainty (standard): 2 mK (Indium, Tin, Zinc) ; 6 mK (Aluminium)
• Heating time: 2 hours
• Inner well diameter: 8 mm
• Immersion depth: 290 mm
• Metal column height: 180 mm
• Dimensions (L x W x H): 430 x 310 x 300 mm
• Mass: 15 kg
• Power supply: 110 VAC or 130 VAC, 50/60 Hz
• Power: 900 W