Why Does Oil Pressure Sensor Drift After Long-Time Oil Exposure Even If It Performs Well at Room Temperature After Potting? Check Medium Penetration and Interfacial Changes First

An oil pressure sensor may pass all room-temperature tests after potting, yet develop zero drift, reduced insulation or sealing failure after prolonged contact with hydraulic oil, lubricating oil and other media. Do not only inspect the sensing chip. Instead, verify whether the potting compound absorbs fluid, swells or softens, and check interfacial integrity between adhesive and metal / plastic substrates. The core requirement for sensor potting adhesives is not strong initial adhesion, but stable performance upon continuous medium exposure. A common misjudgment for this failure mode: Passing all factory tests is mistakenly taken as proof that the potting material is qualified. Oil pressure sensors operate under combined long-term loads: Pressure + Temperature + Vibration + Oil medium. Initial performance only proves the material works right after assembly. 1. Why Failures Only Occur After Oil Immersion Rather Than At Ambient Testing Room-temperature tests only reflect the material’s initial state. Long-term medium exposure requires monitoring: For precision pressure sensors, slight swelling or interfacial variation can alter internal mechanical boundary conditions, even without obvious cracking. Conclusion: Intact adhesive appearance is not sufficient evidence of oil resistance. 2. Possible Material Changes After Oil Intrusion Behaviours vary by polymer system, oil type and operating temperature. Four key changes need evaluation: 3. Why Oil Pressure Sensors Are Vulnerable to Minor Swelling General electronic modules mainly concern water ingress and short circuits. Pressure sensors additionally require stable mechanical loading on sensitive structures. If potting material sits close to: Dimensional change caused by fluid absorption generates residual stress. Such stress may not destroy the component instantly, but leads to: Sensor drift and uncracked adhesive can coexist. 4. Distinguish Bulk Material Failure From Interfacial Failure Judge by failure symptoms: Failure Symptom Priority Investigation Key Validation Items Overall adhesive softening Medium resistance of bulk material Hardness & mass change Obvious…