RH-Combo-Outdoor-Air-Thermistor

Supported Applications

The ACI A/RH Outside Series Sensor is a Relative Humidity transmitter designed for use with electronic controllers in commercial heating and cooling building management systems. The series measures outdoor air conditions, providing data equivalent to 0 to 100% RH. An optional temperature sensor can be included for monitoring space temperature.

Operating Conditions & Performance

The A/RH Outside Series operates within a relative humidity range of 0 to 95% RH, non-condensing (Conformally Coated PCB's), with an operating temperature range of -40 to 140 °F (-40 to 60 °C). Storage is supported from -40 to 149 °F (-40 to 65 °C).

Relative humidity accuracy is specified as +/- 1% over a 20% RH Range between 20 to 90%, or +/- 2%, 3%, or 5% from 10 to 95%. The sensor utilizes a capacitive element with a hydrophobic filter and exhibits less than 2% drift / 5 years stability. Response time is listed as 20 Seconds Typical, with a recommended transmitter stabilization time of 30 Minutes before accuracy verification.

When configured with an optional temperature sensor, performance varies by element type:

• A/1.8K Series Thermistor: +/- 0.5 °C @ 25 °C (77 °F) and (+/-1.0 °C) (+/-1.8 °F)
• A/10K-E1 Series Thermistor: +/- 0.3 °C (+/-0.54 °F)
• All Else (Thermistors): +/- 0.2 °C (+/-0.36 °F) @ 0-70 °C (32 - 158 °F)
• Platinum Sensors: Class A tolerance formula of +/- °C = (0.15 °C + (0.002 * |t|))
• Nickel and Balco Sensors: Accuracy varies by temperature point, e.g., Nickel at 21.1 °C (70 °F) is +/- 0.17 °C (+/- 0.34 °F).

Configuration Options

The series supports field-selectable output signals including 2-wire: 4 - 20 mA (Default), or 3-wire configurations for 0-5 VDC, 0-10 VDC, and 4 - 20 mA. Power supply requirements depend on the selected signal:

• 4-20 mA Output: 15 - 40 VDC / 18 - 28 VAC (with 250 Ω Load) or 18 - 40 VDC / 18 - 28 VAC (with 500 Ω Load)
• 0-5 VDC Output: 12 - 40 VDC / 18 - 28 VAC
• 0-10 VDC Output: 18 - 40 VDC / 18 - 28 VAC

The series is available in two primary enclosure types with distinct materials and dimensions:

• -EH Enclosure (EURO): ABS Plastic with UV Protectant, UL94-VO. Dimensions: Diameter 3.54" (90 mm), Depth 4.30" (109.22 mm). Sensing tube and filter material is 304 Series Stainless Steel.
• -4X Enclosure: Polystyrene Plastic, UL94-V2. Dimensions: Height 4.70" (119.46 mm), Width 3.77" (93.98 mm), Depth 2.23" (56.71 mm). Sensing tube is Schedule 40 PVC (White) with a slotted PVC filter without additional filtration.

Both enclosures carry an NEMA 4X (IP 66) rating. 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). Load resistance limits are 700 Ω maximum for 4-20 mA and 4k Ω minimum for voltage outputs.

Key Product Differences

Variants within the series differ primarily by enclosure style, sensor element type, and calibration options. Model numbers indicate specific configurations:

• Sensor Elements: Models include thermistors (A/1.8K, A/3K, A/AN Type III 10 KΩ nominal, A/CP Type II 10 KΩ nominal, A/50K), platinum sensors (A/100 Ω, A/1K), nickel sensors (1 KΩ nominal), and Balco sensors (1 KΩ nominal).
• Enclosure Suffixes: The "-O" suffix denotes the outdoor air ABS plastic (-EH) configuration. Models with a "-4X" suffix utilize the polystyrene enclosure.
• NIST Calibration: Specific variants include an "NIST" designation, indicating NIST-traceable calibration options are available for certain model numbers (e.g., A/RH2-10KS-O-NIST).