HIGH TEMPERATURE
METAL SHEATHED THERMOCOUPLES

Thermocouple Types:
 
Platinum-Rhodium vs Platinum
Recommended for use in inert or oxidizing atmospheres or for short periods of time in vacuum. Easily contaminated, these elements must be protected from the effects of reducing atmospheres and contaminating vapors.
 
Tungsten vs Tungsten-Rhenium
Recommended for use in vacuum, high purity hydrogen and high purity inert atmospheres only.


Thermocouple Type
Maximum Operating Temperature
 Maximum Exposure Temperature Recommended Environment
Pt-10% Rh/Pt
ANSI Type S
2700°F
1482°C
 3100°F
1704°C		 Oxidizing,
Inert
Pt-13% Rh/Pt
ANSI Type R
2700°F
1482°C
 3100°F
1704°C		 Oxidizing,
Inert
Pt-30% Rh/Pt-6% Rh
ANSI Type B
3100°F
1704°C
 3220°F
1770°C		 Oxidizing,
Inert
W-5% Re/W-26% Re
Type (C)
5000°F
2760°C
 5430°F
3000°C		 Vacuum, High Purity
Hydrogen & Inert
Pt-Platinum, Rh-Rhodium, W-Tungsten, Re-Rhenium

SHEATH SIZE - WIRE GAUGE
Sheath Diameter
Inches		 0.062 0.125 0.187 0.250
Wire Gauge
B & S		 30 30 24 24

Sheath Alloys:

Platinum
Virtually non-oxidizable, soluable only in acids generating free chlorine. Halogens attack it at high temperatures. Malleable. Recommended for use in oxidizing or inert environments. Maximum operating temperature 3000°F.
Platinum 10% Rhodium
Has the character of platinum with increased resistance to corrosion and higher heat strength. Suitable for oxidizing or inert environments. Maximum operating temperature 3100°F.
Tantalum
A reactive and refractory metal. Reactive because it will oxidize above 550°F and refractory because of its extremely high melting point. Suitable for use in inert or vacuum environments. Hard and tough with good ductility. Maximum operating temperature of 4500°F.
Molybdenum
Oxidizes at elevated temperatures. Relatively good hot strength. Suitable for inert, vacuum or reducing environments. Maximum operating temperature of 4000°F.
Molybdenum 50% / Rhenium 50%
Ductile with high hot strength. Suitable in vacuum, hydrogen, nitrogen, cracked ammonia and inert atmospheres. Maximum operating temperature of 4000°F.


Sheath Material Approximate Melting Temperature Maximum Operating Temperature Recommended Environment
Platinum 3217°F
1770°C		 3000°F
1650°C		 Oxidizing,
Inert
Platinum
10% Rhodium		 3362°F
1850°C		 3100°F
1705°C		 Oxidizing,
Inert
Tantalum 5425°F
2996°C		 4500°F
2482°C		 Vacuum
*Molybdenum 4730°F
2610°C		 4000°F
2205°C		 Vacuum,
Inert
*Moly 50%
Rhenium 50%		 4424°F
2440°C		 4000°F
2205°C		 Vacuum, Hydrogen
Nitrogen, Inert
Cracked Ammonia
*Not suitable for swaging.

REFRACTORY OXIDE INSULATORS

The resistivity of metal oxides decreases with increasing temperature. Above 3600°F only Hafnia retains sufficient resistivity for most applications.

Insulator Material Approximate Melt Temperature Maximum Recommended Temperature
Hard-Fired Swaged
Magnesia
MgO		 5070°F
2800°C		 N/A 3400°F
1870°C
Alumina
Al2O3		 3650°F
2010°C		 3200°F
1760°C		 3000°F
1650°C
Hafnia
HfO2		 5126°F
2830°C		 4000°F
2200°C		 N/A

For more information regarding Marlox Thermocouples,
Please consult your Marlin catalog, Pages C-21 to C-44.

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