31050381 HONEYWELL

The 31050381 is a Snap-Action Hermetic Thermostat. The term "hermetic" refers to its vacuum-baked and oxygen-free atmosphere, which is sealed within a metal housing using a glass-to-metal seal at the terminal leads. This design prevents any contamination from moisture or dust from entering the internal contact chamber, ensuring the electrical integrity of the switch over its entire lifespan. The snap-action mechanism ensures that the transition between the "on" and "off" states is instantaneous, which minimizes electrical arcing and radio frequency interference (RFI).

Product Parameters

• Switch Type: Single Pole, Single Throw (SPST)

• Action: Snap-action, automatic reset

• Reset Type: Usually available as "Open on Rise" or "Close on Rise" depending on the specific configuration of the 31050381 sub-model

• Operating Temperature Range: Optimized for ranges between $-29\text{°C}$ and $260\text{°C}$ ($-20\text{°F}$ to $500\text{°F}$)

• Electrical Rating: Typically rated for $5 \text{ A}$ resistive at $28 \text{ VDC}$ or $120 \text{ VAC}$

• Dielectric Strength: $1250 \text{ VAC}$, $60 \text{ Hz}$ for one minute from terminals to case per MIL-STD-202

• Insulation Resistance: $100 \text{ M}\Omega$ minimum at $500 \text{ VDC}$

• Vibration Resistance: Qualified to meet MIL-STD-202, Method 204, $20 \text{ G}$

• Shock Resistance: Qualified to meet MIL-STD-202, Method 213, $100 \text{ G}$

• Housing Material: Stainless steel or cold-rolled steel with a tin/lead or nickel plating

Product Advantages

A primary advantage of the 31050381 is its Military-Grade Durability. Being designed to meet or exceed MIL-S-24236 requirements, it can withstand intense vibration and mechanical shock without losing calibration. The Hermetic Seal is another major benefit, as it allows the thermostat to function perfectly in high-altitude (low-pressure) or high-humidity environments where standard thermostats would oxidize or short-circuit.

Furthermore, the Small Profile and lightweight nature of the 3100 series make it ideal for weight-sensitive applications like satellites or aircraft. The Pre-set Calibration ensures that every unit is factory-tested to trigger at a specific temperature with high repeatability, eliminating the need for field adjustments.

Important Considerations and Precautions

When installing the 31050381, users must ensure Proper Thermal Contact. Since the thermostat senses temperature through its base, any air gap between the mounting surface and the device will result in a delayed or inaccurate response. Using a thermal interface material (TIM) can improve sensitivity.

Because the terminals are glass-to-metal seals, Mechanical Stress on Leads must be avoided; excessive bending or pulling on the terminals can crack the glass seal and compromise the hermeticity. Additionally, do not exceed the Electrical Contact Rating specified; using this device for high-inductive loads without proper suppression circuitry can lead to contact welding. Finally, ensure the device is not exposed to temperatures exceeding its maximum survival limit, as this can permanently alter the snap-point of the bimetallic disc.

Product Applications

The Honeywell 31050381 is utilized in sectors where high-precision thermal management is required.

• Aerospace and Defense: Temperature control for avionics, hydraulic fluid heaters, and satellite battery management systems.

• Medical Equipment: Precise thermal regulation in blood analyzers, incubators, and surgical sterilization equipment.

• Telecom Infrastructure: Over-temperature protection for outdoor base stations and power amplifiers located in harsh climates.

• Energy Sector: Monitoring and controlling temperatures in fuel cells and advanced battery storage systems.

• Laboratory Instruments: Maintaining stable temperatures in gas chromatographs and other analytical sensors.