Thermistor Signal Conditioning in Subsea Data Logging Systems
Pulsed ratiometric excitation and ultra-low tempco references eliminate subsea thermistor self-heating and hydrostatic drift down to millikelvin accuracy.
Input Leakage Current
Meaning
Unwanted current that flows into or out of the input terminals of an electronic device represents a common source of signal distortion. This parameter, designated as input leakage current, occurs due to the non-ideal insulation of semiconductor gates and electrostatic discharge protection structures. It determines the minimum signal level that can be accurately measured without introducing significant calibration errors.
Semiconductor Behavior
Integrated circuits rely on sub-micron gate oxides that are subject to quantum tunneling and leakage. At elevated operating temperatures, the resistance of these insulating structures decreases, leading to an increase in input leakage current. This behavior can degrade the performance of high-impedance sensors used in industrial monitoring systems.
System engineers must choose components with leakage specifications that remain stable across the entire operating temperature range.
Circuit Impact
Sensor signals can be significantly altered when flowing through high-impedance feed networks. In a typical signal conditioning path, input leakage current creates an unwanted voltage drop across the source resistance, which introduces a measurement offset error. This offset can compromise the accuracy of voltage-mode transducers used in precision process control.
The error becomes especially severe in long-term data collection systems where power-saving sleep modes are used. Consequently, high-value contracts for precision modules often specify maximum leakage tolerances under worst-case thermal conditions.
Measurement Technique
Precision instrumentation is required to quantify these sub-nanoampere currents. Engineers use electrometers or specialized source measure units to characterize the leakage behavior under varying common-mode voltage conditions. This validation confirms that the input leakage current remains within the limits specified in the supplier’s datasheet, protecting the buyer against substandard semiconductor batches.