- The DHS29 is designed for extreme applications in Ferrous and Non Ferrous Metal, the DHS29 and 35XT Heat Spy models are built from the bottom up for precise, accurate measurement of high temperatures under the toughest factory conditions. The DHS29 Series measures through glass ports, flames, and products of combustion. High temperature range: 900° to 3200°F (482° to 1760°C). Narrow spectral range for general purpose, high temperature measurement through glass. Small target resolution and long telescopic range. Aim through ports in furnace walls at refractories, glass gobs, furnace tubes, ceramics, billets, slag, and annealing materials. Sapphire window protects the silicon optics from heat and contamination. 3 Year Warranty. Enclosed Optical Sight.