Differential Ratio
An instantaneous rate of change in current with respect to voltage defines the behavior of a non-linear circuit element. Within a sensor circuit, dynamic conductance represents the slope of the current-voltage curve at a specific bias point. It is distinct from total conductance because it isolates the response to small fluctuations from the bulk resistance.
Phase Response
The value fluctuates notably when measured across varying operational frequencies. High frequency signals reveal parasitic capacitance and inductance that remain hidden during direct current testing. Standard test protocols often specify a reference frequency (usually 1 kHz) to ensure comparability between discrete sensor batches.
Instruments must compensate for these reactive components to isolate the real part of the admittance.
Small Signal
Small signal approximations depend on the amplitude of the excitation voltage remaining below a specific threshold. If the perturbation exceeds the linear region of the device, the resulting dynamic conductance value introduces harmonic distortion.
Hardware Verification
Precision source measure units track the derivative of the current through numerical or hardware differentiation. Noise in the current measurement propagates through the derivative, requiring low pass filtering to stabilize the output. Calibration involves verifying the instrument against a known resistive standard at multiple bias points.
An automated sweep across the voltage range identifies the transconductance peaks characteristic of specific gas-surface interactions.
