Gas Sensor Guard Pattern Leakage Current Suppression

A guard pattern is introduced as an intermediary conductive structure between the signal input pattern and different potential patterns. This guard pattern acts as a mediator that intercepts and redirects leakage current, preventing it from reaching the signal input pattern. The guard pattern is maintained at a constant potential through connection to the signal input terminal, creating an equipotential region that eliminates the potential difference driving leakage current across the insulating substrate.

The guard pattern is electrically connected to the signal input terminal, ensuring it maintains the same potential as the signal input pattern. This creates an equipotential condition between adjacent conductive regions, eliminating the potential difference that drives leakage current through the insulating substrate. By making adjacent conductive elements equipotential, the harmful leakage current is suppressed without requiring special substrate materials.

The guard pattern serves as an intermediary protective structure that does not require complex circuitry or additional active components. It is simply a conductive pattern on the substrate that is electrically connected to the signal input terminal, providing passive protection against leakage current and electrical noise while maintaining circuit simplicity.

The input impedance of the connection terminal is set to 500 kΩ or higher, which is a specific parameter change that optimizes the circuit for measuring weak sensor currents. This high input impedance minimizes the loading effect on the sensor while the guard pattern compensates for the increased susceptibility to leakage current that would otherwise result from the high impedance configuration.

Rather than changing the substrate material properties, a guard pattern is introduced as an intermediary conductive element that actively manages leakage current. This approach maintains compatibility with standard glass epoxy resin substrates while achieving low leakage current through the guard pattern's current-redirection function.

The leakage current that would normally flow through the insulating substrate under high temperature and humidity conditions is intercepted and redirected by the guard pattern. The guard pattern converts the harmful leakage current path into a controlled current flow that maintains the guard pattern's equipotential condition, thereby neutralizing the harmful effect without requiring special substrate materials.