Support Center: Guides & FAQs

An unstable dew point reading usually means the moisture conditions at the sensor are changing or the measurement conditions are unstable. Possible causes include system instability, poor installation, contamination, or electrical interference.

Possible causes:

• Pressure fluctuations or pulsations affecting the sensor
• Unstable or insufficient sample flow
• Dead volume or poor sample line design
• Condensate, oil mist, or contamination reaching the sensor
• Rapid dryer cycling or changing process conditions
• Insufficient stabilization time after startup or humidity changes
• Electrical noise, poor grounding, or signal interference
• Faults in the analog reading device or wiring

Recommended checks:

• Verify stable pressure and flow conditions
• Inspect installation point and sample line design
• Check upstream filtration and drainage
• Inspect wiring, shielding, and grounding
• Allow enough stabilization time
• Compare with a reference instrument if necessary
• Check for electrical noise using a multimeter or oscilloscope if suspected

• 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.

• 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.

A desiccant dryer, also called an adsorption dryer, removes moisture from compressed air using a porous drying material such as silica gel or activated alumina.

Compressed air flows through a bed of desiccant. The material adsorbs water vapor, trapping moisture on its surface while the dry air passes through. This process allows the dryer to achieve very low dew points, typically down to −40 °C or lower.Once the desiccant becomes saturated, it must be regenerated. This is usually done in two ways:
• Heatless (pressure swing) regeneration: a small amount of dry air is used to purge and remove the stored moisture.
• Heat regeneration: the desiccant is heated to release the moisture.

Most desiccant dryers use two drying chambers, allowing one to dry the air while the other regenerates the desiccant. This ensures a continuous supply of dry compressed air.

Desiccant dryers are commonly used in applications where very dry air and high air purity are essential, such as manufacturing, laboratories, and moisture-sensitive processes.

A refrigerated air dryer removes moisture from compressed air by cooling it until water condenses and can be drained off.

It works on the principle of condensation. The compressed air is cooled inside a refrigeration circuit. Once the temperature drops below the dew point, moisture turns into liquid water, which is automatically removed. The dried air is then slightly reheated to prevent downstream condensation.

Refrigerated dryers offer effective moisture removal, reliable performance, low operating costs, and a simple design. They are easy to install and maintain and are suitable for many applications such as manufacturing, automotive, pharmaceuticals, and food and beverage.

Their limitations appear at very low dew points, as they typically reach around plus three degrees Celsius. The refrigeration system also requires energy to operate.

Overall, refrigerated air dryers are a cost effective and versatile solution for drying compressed air in a wide range of industrial environments.

Atmospheric dew point is the dew point at no pressure under normal ambient conditions, such as in expanded compressed air. If the air is compressed the moisture contained therein is forced into a smaller volume. Thus, the moisture per unit of volume increases so does the dew point. The pressure dew point is always measured under pressure.