ASTM E452 is the standard test method for calibrating refractory metal thermocouples using a radiation thermometer as the standard instrument. This test procedure is suitable for thermocouple calibrations above 800 °C (1472 °F).
ASTM E452 Standard Test Method for Calibration of Refractory Metal Thermocouples Using a Radiation Thermometer
What is ASTM E452?
What is the Scope of ASTM E452?
The ASTM E452 test technique provides a consistent approach for calibrating refractory metal thermocouples against a calibrated radiation thermometer. This test procedure is designed for thermocouples that cannot be subjected to an oxidizing atmosphere. This test technique is intended for use by wire producers and thermocouple manufacturers for refractory metal thermocouple certification. This test technique is fundamentally limited by uncertainty in the calibration and operation of the radiation thermometer, as well as by the proper construction and use of the test furnace.
- Purpose: Calibration of refractory metal thermocouples by utilizing a calibrated radiation thermometer as the reference standard instrument.
- Atmospheric parameters: Applicable to thermocouples unsuited for oxidizing environments, typically operating in vacuums, inert gases, or reducing gases
- Temperature range: Applicable for calibrations conducted at temperatures above 800°C (1472°F).
- Thermocouple assemblies: Types 1, 2, and 2A (ranging from bare-wire with gas/vacuum insulation to loose and hermetically sealed ceramic-insulated assemblies) and Types 3 and 4 (include swaged sheathed assemblies with compressed refractory powder and coaxial assemblies with a protection tube).
ASTM E452 Sample Preparation and Equipment
The ASTM E452 test process employs refractory metal thermocouples as test specimens. A calibrated radiation thermometer is used as the reference standard instrument.
ASTM E452 Testing Procedure and Requirements
The thermocouple is calibrated in accordance with ASTM E452 by measuring the temperature of its measuring junction using a radiation thermometer and recording the thermocouple’s emf at that temperature. The thermocouple measuring connection is put in an equalizing block with a chamber that approximates blackbody conditions. The cavity in the equalizing block is sighted with the radiation thermometer, and the blackbody temperature or true temperature of the block, including the measuring junction, is determined.
ASTM E452 Results Analysis and Interpretation
The emf difference for each calibration point is ∆E = Er – E, where Er is the table value of emf, and E is the emf of the test thermocouple at the temperature of the calibration point, according to ASTM E452.
Updated on September 4, 2026
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