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.
Insulation Resistance
Meaning
Electrical integrity measurements of insulating materials determine the prevention of current leakage in conductive systems. Monitoring insulation resistance is necessary in subsea applications where exposure to high-pressure saltwater can rapidly degrade electrical barriers. The boundary of this metric is the maximum voltage the insulation can withstand before dielectric breakdown occurs.
Measurement Procedure
Testing involves applying a high direct-current voltage across the insulating layer and measuring the resulting tiny leakage current. Special instruments known as megohmmeters are required to measure these values, which typically range from megohms to gigohms. The measurement must be taken over a standardized period to allow capacitive charging currents to subside, ensuring a stable and repeatable reading.
Environmental Degradation
High humidity and saltwater exposure are the primary drivers of insulation failure in maritime environments. Microscopic cracks in cable jackets allow moisture to penetrate and create low-resistance paths to the ground. This degradation leads to instrument failure and can cause hazardous electrical faults on the vessel.
Testing Threshold
Preventive maintenance schedules require regular testing to identify gradual declines in resistance before total failure happens. A sudden drop indicates immediate degradation, necessitating the replacement of the affected cable. These thresholds are defined in industrial standards to ensure consistent safety margins across all onboard equipment.