Spatial Thermal Gradient Mapping Micro-Machined Accelerometer Arrays
Spatial thermal gradient mapping in micro-machined accelerometer arrays decouples linear motion from external board heat using differential thermopile matrices.
Helium Cavity
Thermal Reservoir
Sealed internal volumes within a sensor housing contain a light inert gas to facilitate heat transfer or detect leaks. A helium cavity provides a stable environment where the high thermal conductivity of the gas assists in rapid equilibration between internal components. The low atomic mass of the gas allows it to permeate small gaps that larger molecules cannot enter.
This property makes the cavity an excellent tool for verifying the integrity of hermetic seals.
Leak Detection
Monitoring the escape of gas from the helium cavity allows for the quantification of leak rates in vacuum-sealed packages. Sensitive mass spectrometers detect the presence of the gas in an external chamber to find failures in the housing. This test is a standard part of the qualification for aerospace grade electronics.
Gas Selection
Pure helium is chosen for its inert nature and its predictable behavior under pressure. Unlike air, the gas in a helium cavity does not support oxidation or moisture-related corrosion inside the device. It maintains a constant dielectric property over a wide range of temperatures.
Pressure Maintenance
Internal pressure within the helium cavity must be monitored to ensure the thermal properties remain consistent. If the gas density changes, the heat transfer rate between the sensor and the environment will shift. Such shifts are interpreted as drift in the primary measurement signal.