07 — Temperature variation: 5 and 10 °C per minute in practice

DO-160 Display Qualification | A-P02 — Draft / Not Released

Learning objective: Specify ramp evidence and diagnose thermal lag without substituting a different method.

What the ramp rate describes

DO-160G Section 5 Categories A, B and C use minimum chamber temperature-change rates of 10, 5 and 2 °C/min respectively. The category designation belongs to Section 5; it is not the Section 4 temperature category. S1/S2 temperature-shock categories address changes greater than 10 °C/min using their own procedures and distinctions. Read the exact adopted definitions and tolerances.

The A/B/C procedure includes at least two cycles and more if needed to complete the required performance checks. The endpoints, stabilization, powered transitions and prescribed power-off/restart stages matter as much as the nominal slope. A purchasing sentence that specifies only ten cycles at 10 °C/min is incomplete.

Thermal lag and failure mechanisms

The panel does not necessarily follow chamber air at the same rate. Mass, enclosure conduction, heater control and airflow affect its response. Differential expansion can stress the optical bond, cover glass, panel supports, flex tails and solder joints. A chamber that changes quickly while the assembly barely changes may still follow a defined chamber-based method, but its actual traces are needed to interpret development evidence and any additional component requirement.

Look for image nonuniformity, bubbles or edge separation, touch drift, intermittent connectors and new contamination. Use reference photographs and numeric criteria at repeatable conditions. Distinguish reversible cold response from lasting damage, while still applying any during-exposure requirement.

Exercise: apparent equivalent cycles

Supplier A reports 100 slow cycles at 1 °C/min. Supplier B reports the required Category B sequence at 5 °C/min. Does A's larger cycle count establish the same qualification? Worked response: no. It can be useful development or durability evidence, but rate, endpoints, power state, stabilization and the required functional checks must be compared. More cycles do not automatically cover a different thermal-gradient exposure.

Record checklist

Save chamber and selected equipment temperature traces, actual transition rates, cycle markers, power events, functional data and anomalies. State rate calculation intervals and the method used to determine stabilization. Review the profile before issuing a pass so insufficient transitions or missing restart checks can be dispositioned while the setup remains available.

Section 5 rates and the selected transition example

At ambient stabilization, perform the required compliance checks in the second or last cycle as applicable. Monitoring during transitions, any additional cycles, condensation control and permitted inter-cycle breaks must follow §5.3.1. This sequence is not a combined Section 4/5 procedure.