Potting compound for outdoor sensors
Outdoor sensors are constantly exposed to moisture, UV radiation, temperature fluctuations, and various media. Encapsulation reliably protects the electronics – but must not impair the measuring function. This delicate balance determines the choice of material.
To the point
For outdoor sensors, a soft, UV- and weather-resistant silicone or gel is suitable in most cases : it is watertight (IP67/IP68), low-stress, and resistant to sun and moisture. It is crucial that measuring membranes or optical windows are not incorrectly potted – not every part of a sensor can withstand a rigid potting compound.
Protect without killing the function
The key point with sensors is that protection and measurement function can conflict, and the measurement principle determines the potting strategy. The diaphragm of a pressure sensor must not be rigidly encased – here, a soft gel the pressure with virtually no loss, without distorting the measurement. An optical window must remain unobstructed or be covered with a clear material. Capacitive and inductive sensors, on the other hand, can usually be completely encased. A hard mass over a sensitive element creates drift, mechanical stress, or blocks the measurement entirely.
| Measurement principle | Potting strategy |
|---|---|
| Pressure / Force (membrane) | soft gel on the membrane, pressure-transmitting; never rigid |
| Optical / IR | Leave windows clear or use clear material; protect electronics separately |
| Capacitive / inductive | Full encapsulation is usually unproblematic; ensure constant dielectric strength |
| temperature | good thermal contact with the medium, thin layer over the sensor |
The stresses in the outdoor area
Sealing
Protection ratings such as IP67 or IP68 are defined according to IEC 60529. A tight, full potting compound, including the cable exit, is the most reliable way to achieve this – provided the compound adheres to the housing and cable sheath. Permanent immersion resistance (IP68) also requires a cable entry point with a secure bond.
UV radiation and weathering
Prolonged exposure to sunlight causes many polyurethanes and epoxies to yellow and become brittle. Silicones are UV and weather resistant and remain elastic for years – the safe choice for long-term outdoor use.
Temperature changes and condensation
Day-night and seasonal cycles generate condensation and mechanical stress. A wide temperature range and low-stress operation keep the sensors stable; a tight potting compound prevents condensation from reaching the electronics.
Media and salt spray
Cleaning agents, splash water and salt spray (tested e.g. according to ISO 9227) as well as cyclic moist heat stress (IEC 60068-2-78) require chemical and hydrolysis resistance – strengths of silicone.
Material selection and products
Sensitive or pressure-measuring sensors: soft gels and soft types such as SILISIL RTV MD-Gel, MD-Soft 10 or MF-Soft 12.More robust assemblies without a sensitive membrane: elastic, castable silicones such as MF-Flex 20 or PRO-Cast 45.For the fundamental distinction between full and partial potting, see Potting vs. Encapsulation.
processing
Clean, apply adhesion promoter if necessary, mix thoroughly, degas, and cure according to the data sheet (step-by-step instructionsto avoid errors). Determine the required material quantity using the potting and mold making calculator.
Frequently Asked Questions
Can I pot a pressure sensor? Only the electronics, not the rigid diaphragm. Use a soft, pressure-transmitting gel over the diaphragm to ensure the measurement signal is maintained.
Why not just use epoxy? Epoxy yellows and becomes brittle under UV light and, due to its rigidity, transmits stresses to the sensors – usually the worse choice for outdoor use.
Is a protective coating sufficient? For light splash water protection, sometimes yes; for IP67/IP68 and mechanical protection outdoors, a full potting is more reliable.
Consultation and samples
Tell us the sensor type, measuring principle, installation requirements, and environmental conditions – we will recommend the appropriate type and provide a sample. Contact us or write to info@silitech.ch.
