Front Surface Pyrometer.

Principal users of the Tri-Service Thermal Flash Test Facility (TFTF) were surveyed to determine their perceived need for noncontact front surface temperature measurements on specimens being tested at the facility. Performance specifications and operational capabilities which define a radiation pyrometer system satisfactory for use at TFTF were developed from the results of this survey. All of the principal specifications were satisfied by a long waveband infrared (8-11.5 micrometer) pyrometer, which was modified by the manufacturer to meet TFTF time response requirements. The pyrometer was further modified by the addition of a water-cooled radiation channel to restrict the instrumental field of view to a size compatible with the space available in the test chamber. Tests of the radiation pyrometer were performed at the TFTF with a high emissivity copper specimen. The tests show good correlation between front surface temperatures measured with the pyrometer system and back surface temperatures measured with thermocouples when allowance is made for temperature gradients generated in the specimen plate. Preliminary tests with a low emissivity specimen show that test chamber background may be a serious problem for temperature measurements on highly reflective surfaces. Keywords: Front surface temperature measurement; Emissivity; Infrared pyrometer; Noncontact temperature measurement; Radiation pyrometer system.