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The Nova 257 Series Continuous Dew Point Analyzers have been designed primarily for accurate dew point measurement of exothermic/endothermic heat treating atmospheres and other similar applications.

The dielectric polymer sensor provides stable and accurate dew point measurements and is not affected by most
gas compositions. A built-in sample pump draws in samples that are of insufficient pressure from the
process. The sample flow is shown on a small rotameter with valve. The analyzer then reads the dew point

Depending on the application, the following models may be relevant:

• 257N4: applications at atmospheric pressure
• 257CAA-B - compressed air applications 5 to 125 psig
• 257CAA-C - compressed air applications 5 up to 3000 psig
Unit of Measure


Method of Detection

N/A Dielectric polymer sensor that changes capacitance with moisture variation

Ranges Available

N/A -40°F to +104°F (-40°C to +40°C) Dew Point


N/A ±1°F (1°C) Dew Point

Accuracy & Repeatability

N/A ±1°F (±1°C) Dew Point


N/A Less than 1% of full scale per month

Response Time (T-90)

N/A Less than 60 seconds after initial purge down

Ambient Temperature Range

N/A -18 to 49 ºC0 to 120 ºF


N/A Better than 1°F (1°C) Dew Point

Size & Weight

N/A Approx. 51 x 41 x 26 cm @ 10 kg (20" H x 16" W x 10" D @ 20lbs)


N/A 115 VAC, 60 Hz 220 VAC, 50 Hz also available

Output Options

N/A 4-20mA output, isolated or non-isolated


N/A High or low dew point alarm with relay contact

Hazardous Area Rating Options

N/A General Purpose, Non-Hazardous



    For continuous dew point analysis at atmospheric pressure of air, heat treat furnace gases, compressed air lines and other applications with oils or contaminants present.



  • Standard range of -40 to +68°F (-40 to +20°C) dew point. Other ranges and units of measure available on request
  • Rugged design that is easy to operate
  • Use on any non-corrosive gas
  • Long-life dielectric polymer sensor
  • May be calibrated in the field
  • Bright digital readout
  • Built in sample pump, filter, and flow meter
  • NEMA 4 enclosure is standard
  • Sensor easily replaced if contaminated
  • Factory calibrated to NIST traceable standards



  • Compressed Air Configuration for dew point at line pressure
  • 4-20mA recorder output
  • Calibration kit
  • Carbon potential calculation, using input from customer-supplied Type K thermocouple



  • Calibration is easily performed in the field using the optional calibration kit (Part no. NDPCK-02)
  • Alternatively, the analyzer may be returned to Nova for a certified calibration

Unique Applications


    The 257 Series should not be used to measure dew points when corrosive gases are present. All Nova analyzers are built using proven technologies and techniques. If this product does not suit your application, please contact Nova. In many cases, we are able to build an analyzer specific to your needs.

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