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Dew Point: The Sensors, Their Function, and What We Offer

When it comes to industrial applications, dew point sensors are beginning to play a more critical role. In applications such as compressed air systems, air pressure pipelines, and drying processes, dew point sensors are being used. Why?

Well, to begin, we should assess what dew point actually is:

What Is Dew Point?

Dew point is the temperature at which water vapors in the air form dew or frost. The air can only hold so much water vapor before condensation occurs in any application at any temperature. This maximum amount is referred to as water vapor saturation pressure. The addition of water vapor beyond this point results in condensation. 

Many industries need to keep an eye on the amount of condensation produced because the moisture can clog pipes, break machinery, and cause contamination. For this reason, they should select a dew point meter that has the correct measuring range to monitor the dew point.

Examining the Effect of Pressure on Dew Point

Air compression increases water vapor pressure, and by extension, dew point. It’s vital to consider this if you’re bleeding the air into the atmosphere prior to taking a measurement. Dew point at the measurement point will differ from the dew point in the process..

This brings us to the question, “What is a dew point meter?”

What Is a Dew Point Sensor?

Dew point sensors, or condensation monitors, are utilized in building technology to assess the risk of condensation forming. They are typically placed on climate-controlled ceilings, in pipelines or control cabinets, before it can result in damage.

How Do Dew Point Sensors Work?

Dew point sensors work through impedance. The sensor is composed of layers; two electrodes on either side of an absorbent layer. As gas passes over the sensor, it absorbs water vapor onto a porous hygroscopic dielectric area between conductive layers built atop a base ceramic substrate. Water molecules change the dielectric constant (K), which results in a change in the sensor’s impedance. 

Common Dew Point Monitoring Applications

Reliable dew point sensors enable high-precision dew point measurement predicated on the hygrometric measuring principle, and are ideal for:

  • Early condensation detection on surfaces
  • Dew point measurement in compressed air systems, industrial drying processes, and refrigeration dryers
  • Mobile, selective dew point measurement — via hand-held meter technology — for HVAC applications.

Dry compressed air is critical for many industrial processes. For this reason, plants are installing

dew point measuring instruments to protect equipment, save energy, and prevent over-drying.

Some of the applications where dew point monitoring is used include:

Medical and breathing air

When it comes to most medical gas and breathing air regulations that guarantee safe breathing conditions for everyone from patients to firefighters, dew point monitoring is required for compliance.

Plastics drying

Maintaining adequate dryer performance prevents wasted materials and production downtime — all while ensuring product quality

Food and pharmaceutical industries

Numerous applications within the food and pharmaceutical industries utilize compressed air. Standard applications include coating quality control, filling, and packaging.

Mass Transit

Brakes, doors, and AC systems on trains, buses, and other mass transit vehicles rely on dew point measurement in their compressed air for safety and reliability.

Our Dew Point Sensors

At JLC International, we sell a range of dew point transmitters which include the following. Please keep in mind that the dew point sensors offered by JLC International have applications with different engineering units, dependent upon the setup of this instrumentation:

  • Shaw SDT
    • Various Dewpoint ranges over -100 to +20 °C (-148 to +68 °F)
    • Accuracy of ± 2.0 °C (± 3.6 °F) dew point temperature
    • Output of 4 – 20 mA, 2-wire loop powered, 24 Vdc
    • Weight of 0.385 lbs
    • Weather-proof rating NEMA 4X (IP66 )
    • This dew point sensor is factory calibrated and traceable to international standards.
    • The performance of this technology is not affected by flow rate or pressure.
  • Shaw SDT-Ex
    • Various Dewpoint ranges over -100 to +20 °C (-148 to +68 °F)
    • Accuracy of ± 2 °C (± 3.6 °F) dew point temperature
    • Output of 4 – 20 mA, 3-wire technology, 24 Vdc
    • Intrinsically Safe to ATEX standards
    • Weight of 0.55 lbs (250 g)
    • Weather-proof rating NEMA 4X (IP66 )
    • This dew point sensor is factory calibrated and traceable to international standards.
    • The performance of this technology is not affected by flow rate or pressure.
  • Mini EE354
    • Designed for refrigeration dryers
    • Dewpoint range -20 to +50 °C (-4 to +122 °F)
    • Accuracy of ±1 °C (± 1.8 °F)
    • Output of 4 – 20 mA, 3-wire technology
    • ModBus RTU Digital interface
    • Weather-proof rating NEMA 4X (IP65)
  • OEM EE355
    • Dewpoint range -60 to +60 °C (-76 to 140 °F)
    • Accuracy of ≤ ±2 °C (± 3.6 °F)
    • Output of 4 – 20 mA, 3 wire technology
    • ModBus RTU Digital interface
    • Weather-proof rating NEMA 4X (IP65)
  • Compact EE371
    • Dewpoint range -60 to +60 °C (-76 to 140 °F)
    • Accuracy of ≤ 2 °C (3.6 °F) / 5 ppm + 9% of reading
    • 2 scaleable analogue outputs: Td, Tf or X(v)
    • 2 potential free relays
    • Auto-calibration
    • LC Display (optional)

For more information on our dewpoint sensors or other products, like our industrial flow meters, don’t hesitate to contact us. We’ll be happy to answer any questions you have or assist you in placing an order.