AMS (Aerospace Material Specifications) 2750E is a pyrometry specification (temperature driven) which used procedures, timelines, calibration information and record-keeping as well as specific thermocouple choices and temperature uniformity surveys.  When designing a furnace, an end user needs to make the builder aware of the need to meet AMS 2750E so that the furnace is built with those components that allow for the procedures/record-keeping, etc.... to be followed.