RH-Room

Supported Applications

The ACI Relative Humidity Room Series is a relative humidity transmitter designed for use with electronic controllers in commercial heating and cooling building management systems. The series utilizes a thermoset polymer capacitive sensing element featuring a factory-fitted hydrophobic filter to improve moisture resistance. This multilayer construction provides excellent resistance in applications where dust, dirt, oils, and common environmental chemicals are present.

Operating Conditions & Performance

The series measures relative humidity across a range of 0-100% with an operating RH range of 0 to 95% RH, non-condensing. Accuracy specifications vary by model selection: +/- 1% over a 20% RH Range between 20 to 90%, or +/- 2% and +/- 3% from 10 to 95%. The operating temperature range is 35 to 122 °F (1.5 to 60 °C), with a storage temperature range of -40 to 149 °F (-40 to 65 °C). Performance characteristics include an RH response time (T63) of 20 Seconds Typical, repeatability of less than 2% drift / 5 years, and sensitivity/resolution of 0.1% RH.

Power requirements depend on the output signal configuration:

• 4-20 mA Output: 250 Ω Load: 15 - 40 VDC / 18 - 28 VAC; 500 Ω Load: 18 - 40 VDC / 18 - 28 VAC (Reverse Polarity Protected).
• 0-5 VDC Output: 12 - 40 VDC / 18 - 28 VAC.
• 0-10 VDC Output: 18 - 40 VDC / 18 - 28 VAC.

The series supports load resistances of up to 700 Ω maximum for 4-20 mA outputs and a minimum of 4K Ω for 0-5 VDC or 0-10 VDC outputs. Electrical connections utilize screw terminal blocks (polarity sensitive) compatible with wire sizes from 16 AWG (1.31 mm²) to 26 AWG (0.129 mm²).

Configuration Options

The series offers configurable options for enclosure style, accuracy class, output signal type, and optional temperature sensing.

• Housing Options: Two enclosures are available: "R" Enclosure (ABS Plastic, Beige) and "R2" Enclosure (ABS Plastic, White). Both feature a UL94-HB flammability rating and four-way airflow to minimize self-heating. Dimensions for both versions are 4.50" (114.3 mm) x 2.75" (69.85 mm) x 1.12" (28.45 mm).
• Output Signals: Units ship from the factory set to a 2-wire 4-20 mA output. Field-selectable options via on-board DIP switches include 3-wire 0-5 VDC or 0-10 VDC outputs.
• Accuracy Classes: Models are available with +/- 1%, +/- 2%, or +/- 3% accuracy ratings depending on the selected RH range and model number (e.g., A/RH1, A/RH2, A/RH3).
• Temperature Sensing Options: An optional temperature sensor can be included. Available thermistor types include 1.8KΩ, 3KΩ, AN (Type III), CP (Type II), and various other resistance values up to 100KS.
• Calibration & Configuration: Single-point field calibration is performed using increment/decrement DIP switches in +/- 0.5% increments. Three-point NIST Calibration Certificates are available as an option, with default test points at 20%, 50%, and 80%. For the +/- 1% models, a five-point certificate within a selected 20% range is also offered.
• Special Configurations: Custom configurations include Room with Override (RO), Room with Setpoint (S), or combinations thereof. These variants support setpoint and override signals via dedicated terminal blocks.

Key Product Differences

The series distinguishes between standard humidity-only transmitters and models integrated with temperature sensors. Standard ordering includes the A/RH1, A/RH2, and A/RH3 model families corresponding to their respective accuracy classes.

• Housing Distinction: The "R" suffix denotes a beige enclosure, while "R2" denotes a white enclosure. Both share identical dimensions and internal specifications but differ in color for commercial decor compatibility.
• NIST Certification: Models with the "-NIST" suffix include a calibration certificate. Standard certificates provide three test points (20%, 50%, 80%), while specific +/- 1% models may offer five-point verification within a defined range.
• Functional Variants: Suffixes such as "O", "S", and combinations like "SO" indicate the inclusion of Override or Setpoint signal capabilities, requiring additional wiring connections for temperature sensor signals (SEN +/ -), set point signals (SET +/ -), and override signals (O/R +/ -).