RH-Outdoor-Air

Supported Applications

The ACI Relative Humidity Outdoor Air series is a relative humidity transmitter designed for use with electronic controllers in commercial heating and cooling building management systems. The sensor utilizes a thermoset polymer capacitive sensing element with a factory-applied hydrophobic filter to provide resistance against moisture, dust, and other chemicals.

Operating Conditions & Performance

The series operates within an ambient temperature range of -40 to 140 °F (-40 to 60 °C) with a storage temperature range of -40 to 149 °F (-40 to 65 °C). The measurement range is 0-100% RH, while the operating humidity range is specified as 0 to 95% RH, non-condensing. Accuracy specifications vary by model configuration: +/- 1% over a 20% RH Range between 20 to 90%, or +/- 2% or 3% from 10 to 95%. The typical response time (T63) is 20 seconds, with stability listed as less than 2% drift / 5 years and repeatability of 0.5% RH.

Configuration Options

The series offers configurable output signals via integral DIP switches for field selection. The default configuration is a 2-wire 4-20 mA signal, with selectable options for 3-wire 0-5 VDC or 0-10 VDC outputs. Power supply requirements depend on the selected load and output type:

• 4-20 mA: 250 Ω Load requires 15 - 40 VDC / 18 - 28 VAC; 500 Ω Load requires 18 - 40 VDC / 18 - 28 VAC.
• 0-5 VDC: Requires 12 - 40 VDC / 18 - 28 VAC.
• 0-10 VDC: Requires 18 - 40 VDC / 18 - 28 VAC.

The series is available in two enclosure types:

• Euro (-EH) Enclosure: Constructed of ABS Plastic with UV Protectant (UL94-V0), featuring a gasketed cover and conformally coated circuit boards. The sensing tube material for -EH enclosures is 304 Series Stainless Steel.
• NEMA 4X (-4X) Enclosure: Constructed of Polystyrene Plastic (UL94-V2), rated NEMA 4X (IP 66). The sensing tube material for -4X enclosures is Schedule 40 PVC (White).

Electrical connections utilize screw terminal blocks that are polarity sensitive, accepting wire sizes from 16 AWG (1.31 mm²) to 26 AWG (0.129 mm²). An optional temperature sensor is available for monitoring space temperature.

Key Product Differences

Variants within the series are distinguished by accuracy class, enclosure style, and calibration certification:

• Accuracy Classes: Models include +/- 1% (RH1), +/- 2% (RH2), or +/- 3% (RH3) specifications.
• NIST Certification: Select models are available with a NIST Certificate providing three-point calibration verification. Default test points cover 20%, 50%, and 80%; specific configurations offer five points within a selected 20% range.
• Enclosure Dimensions: The Euro (-EH) enclosure measures approximately 4.30" (109.22 mm) in diameter with an overall length of 6.52" (165.67 mm). The NEMA 4X (-4X) enclosure has a top view dimension of 4.73" (120.14 mm) x 3.70" (93.98 mm).