Abstract: Various methods and a multiple thermocouple support assembly are disclosed. The support comprises a tube supported at both ends while extending across a vessel used in processing a fluid over a fixed bed of particulate solids, for example, such as a hydrotreating catalyst in fixed bed reactors, in which temperature measurements are required simultaneously at various defined locations in a horizontal plane across the bed. Features of the support include a particular means for mounting thermocouples in thermowells and particular means for securing the thermowells to the support tube, the thermocouples being pressed against the outer wall of each thermowell opposite to the support tube and the thermowells being spaced from each other and from the support tube for obtaining maximum heat conduction from the fluid or fixed bed of particulate solids with a minimum of heat conduction from the thermowell support tube.