Emerson MVME55006E manual Measuring Junction Temperature, Measuring Local Air Temperature, 102

B.3.2 Measuring Junction Temperature

Some components have an on-chip thermal measuring device such as a thermal diode. For instructions on measuring temperatures using the on-board device, refer to the component manufacturer’s documentation listed in Appendix C, Related Documentation.

B.3.3 Measuring Local Air Temperature

Measure local component ambient temperature by placing the thermocouple downstream of the component. This method is conservative since it includes heating of the air by the component. The following figure illustrates one method of mounting the thermocouple.

Figure B-3 Thermalcouple Placement

Tape thermocouple wire to top of component

Thermocouple junction

Air flow

PWB

B.3.4 Measuring Case Temperature

Measure the case temperature at the center of the top of the component. Make sure there is good thermal contact between the thermocouple junction and the component. We recommend you use a thermally conductive adhesive such as Loctite 384.

If components are covered by mechanical parts such as heatsinks, you will need to machine these parts to route the thermocouple wire. Make sure that the thermocouple junction contacts only the electrical component. Also make sure that heatsinks lay flat on electrical components. The following figure shows one method of machining a heatsink base to provide a thermocouple routing path.