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.
Vishay Foil Resistor
Meaning
Electronic components manufactured with metal foil elements bonded to ceramic substrates exhibit extremely low temperature coefficients of resistance and long-term stability. A vishay foil resistor is utilized as a reference element in high-precision measurement circuits, such as oceanographic sensor bridges. Its use is limited to applications where the requirement for precision outweighs the higher cost compared to standard film resistors.
Component Technology
The resistor is constructed by bonding a thin metal alloy foil to a ceramic substrate, followed by precise photo-etching of the resistive pattern. This pattern is designed to minimize inductance and capacitance, making the component suitable for high-frequency applications. The bonding process causes the foil and substrate to undergo opposing thermal expansion behaviors, cancelling out temperature effects and achieving unmatched precision.
Temperature Stability
This design results in a temperature coefficient of resistance of less than one part per million per degree Celsius. It ensures the resistance value remains constant even when the ambient temperature fluctuates.
Sensor Integration
Oceanographic temperature loggers use these resistors as the reference leg in bridge circuits to measure thermistor resistance. Their exceptional stability prevents changes in the instrument’s internal temperature from being misread as ocean temperature variations. They are a standard component in the signal conditioning circuitry of deep-sea instruments.