Signal Chain Reconfiguration for Capacitive and Piezoresistive Transducer Alternates
Reconfiguring signal chains between capacitive and piezoresistive transducers requires matching input impedance, excitation sources, and thermal compensation math.
Low Leakage PCB Layout
Design Architecture
Board level design practices of this class minimize unwanted stray currents between high voltage traces and sensitive high impedance nodes. Implementing a low leakage pcb layout is essential for preserving the resolution of femtoampere-level sensor circuits. This design applies to electrometer inputs and pH sensors.
Low impedance circuits do not require these measures. Proper spacing and trace routing must be maintained on all layers.
Guard Ring
Copper rings are routed around high impedance nodes and driven to the same potential as the signal trace. This blocks leakage current from adjacent high voltage paths. The ring acts as a barrier.
It absorbs stray current before it reaches the sensor node.
Material Properties
Substrate selection determines the baseline resistance of the circuit board under humid conditions. PTFE or high performance epoxy laminates reduce bulk leakage. Surface finish must remain free of flux residue.
Solder mask is often removed from critical areas.
Testing Method
Isolation resistance is measured using a specialized megohmmeter or source measure unit in a controlled environment. Technicians apply a high voltage to check for insulation breakdown. This test occurs during quality assurance testing.
The layout must prevent any current from bypassing the guard ring.