This instrument is used for high temperature aging test or dimensional change rate test of plastic pipes, pipe fittings, sheets and profiles, and can also be used for baking, drying heat treatment and other heating purposes in laboratories or factories; the bypass hot air circulation system is adopted to avoid the direct radiation of the sample by the heat source, and the temperature inside the box is uniform. The temperature control adopts intelligent PID adjustment technology, the temperature is accurate and the operation is simple. Compliant with standards: GB/T6671, GB/T11158, GB/T2423.2, etc.