Dew point sensors can respond slowly when the moisture diffusion to the sensing layer is limited or when the sensor must recover from previous exposure to high humidity.
Possible causes:
  • The sensor was previously exposed to very wet air and needs recovery time.
  • Contamination such as oil, particles, or chemicals is slowing moisture exchange at the sensing surface.
  • The sample flow is too low or stagnant.
  • The sensor is installed in a dead-leg or in a point with poor air exchange.
  • The sensing element has aged and no longer meets its original response specification.
Technically correct checks:
  • Verify that sufficient sample flow reaches the sensor and that the measuring point is representative.
  • Check whether the sensor has been exposed to condensate or oil contamination.
  • Compare response after a process step change with the expected sensor behavior from the datasheet.
  • Clean or service the sampling system if applicable, but do not damage the sensing element.
  • Recalibrate or replace the sensor if long-term drift or aging is suspected.