How often should capacitive sensors be calibrated?

It varies by industry and environmental conditions. Every 6 months for pharmaceutical and cleanroom applications, annually for general industrial use, and every 2 years for HVAC and building management. In chemical vapor-laden environments, this period can be shortened to 3 months.

What type of salt should be used for humidity sensor calibration?

Different salts are selected based on calibration purpose. LiCl for low humidity calibration (11%), MgCl₂ or Mg(NO₃)₂ for mid-range, NaCl for high humidity reference (75%), and K₂SO₄ for very high humidity (97%). All salts must be of analytical purity grade.

How can I tell if a sensor is reading incorrectly?

Look for inconsistent readings compared to a reference sensor, discrepancies with process results, sudden spikes or abnormal flatness in trend analysis, and extended response times. The most reliable method is field comparison with a calibration-certified reference sensor.

Should I choose a capacitive sensor or a psychrometer?

Capacitive sensors have become the industrial standard due to their ease of maintenance, compact size, and electronic integration advantages. Psychrometers are preferred in chemical environments and for reference calibration measurements. Capacitive sensors are more practical for continuous automation applications.

What is the difference between IP65 and IP67?

IP65 is protected against water jets from all directions. IP67 can withstand submersion in 1 meter of water for 30 minutes. IP69K may be required in food industry areas with CIP cleaning. The worst-case scenario should also be considered when selecting.

Can a humidity sensor be cleaned?

Yes, but extreme care is required. Mechanical cleaning of the sensor element is prohibited; light blowing with compressed air is acceptable. After cleaning, at least 24 hours of pre-conditioning and calibration verification is required.

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Related Glossary Terms

For deeper definitions of the technical concepts in this article, browse the related entries in the NKT Glossary:

Relative Humidity (RH)Absolute Humidity Dew Point Wet Bulb Temperature Cleanroom Modbus (RTU/TCP)BMS (Building Management System)Calibration HVAC (Heating, Ventilation & Air Conditioning)GMP (Good Manufacturing Practice)ASHRAE (American Society of Heating, Refrigerating and AC Engineers)ACH (Air Changes per Hour)SCADA (Supervisory Control & Data Acquisition)Setpoint (Target Value / Set Point)HACCP (Hazard Analysis & Critical Control Points)ISO 14644 (Cleanroom Classification)Sorption (Adsorption + Absorption)VFD (Variable Frequency Drive)Chloride (Cl⁻)Humidity Sensor

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