RH-Combo-Outdoor-Air-Temp-Transmitter

Supported Applications

The ACI Relative Humidity with Temperature Outside Air series is a combination transmitter that measures outdoor air humidity and temperature for commercial heating and cooling building management systems. It uses a thermoset polymer capacitive sensing element with a factory-applied hydrophobic filter, which adds resistance to moisture, dust, and other chemicals for greater long-term outdoor reliability.

The transmitter delivers a proportional 4 to 20 mA current signal or a field-selectable voltage signal to electronic controllers. Because it is intended for outdoor mounting, guidance is to mount it in shade on the north side of the structure, at least 4' (1.22 m) above ground, so solar and thermal radiation do not affect the reading.

Operating Conditions & Performance

The RH measurement range is 0 to 100%, with an operating range of 0 to 95% RH, non-condensing. At 77 °F (25 °C), RH accuracy is ±1% over a specified 20% range between 20 to 90% RH, or ±2% or 3% from 10 to 95%. The capacitive RH element has a T63 response time of 20 Seconds Typical, while the platinum RTD responds in 8 Seconds nominal, and RH stability is less than 2% drift over 5 years.

The platinum RTD outputs 100 Ohms at 32 °F (0 °C) on TT100 versions and 1000 Ohms on TT1K versions, with Class A accuracy of ±0.06%. Temperature accuracy is ±0.2% for spans of 500 °F (260 °C) or less and ±0.5% for larger spans.

• Output: 4 to 20 mA (2-wire, loop powered) with field-selectable 0-5 VDC or 0-10 VDC (3-wire), and a temperature output of 1-5 VDC or 2-10 VDC.
• Supply: 8.5 to 32 VDC (reverse polarity protected) at 25 mA minimum; a 250 Ohms load requires 13.5 to 32 VDC and a 500 Ohms load requires 18.5 to 32 VDC.
• Output load: 700 Ohms maximum on 4 to 20 mA, or 4K Ohms minimum on the voltage outputs.
• Operating temperature: -40 to 140 °F (-40 to 60 °C); storage -40 to 149 °F (-40 to 65 °C).
• Sensing tube: 4.73" (120.14 mm) long by 0.845" (21.46mm) in diameter, ASA/PC FA-30 material.
• Enclosure: NEMA 4X (IP 66) polystyrene plastic, UL94-V2, rated -40 to 158 °F (-40 to 70 °C).

Wiring is to polarity-sensitive screw terminal blocks accepting 16 to 26 AWG conductors, and each transmitter has a recommended stabilization time of 30 minutes before accuracy verification.

Configuration Options

Every model in this series shares the capacitive RH sensing element, hydrophobic filter, platinum RTD, and 4 to 20 mA output in an outdoor-air NEMA 4X enclosure. Models differ by accuracy grade, temperature-sensing element, transmitter output, and calibration options.

Accuracy Grade

The RH1, RH2, and RH3 codes select accuracy: RH1 is ±1% over a specified 20% range between 20 to 90% RH, RH2 is ±2%, and RH3 is ±3%.

RTD Element

The model series code sets the temperature element: TT100 uses a 100 Ohms platinum RTD and TT1K uses a 1000 Ohms RTD, while the TTM100 and TTM1K matched versions add a factory NIST calibration, with 3 point or 5 point certification available.

Options

All models use the O outside-air configuration in a 4X enclosure, and additional options such as an extended 3.25" probe or a POTTED build are available on selected models for demanding installations.

Key Product Differences

A catalog number is assembled from the A/ sensor series prefix, the accuracy grade, the model series, the O outside-air configuration, the 4X enclosure, the transmitter output, and the calibrated span. For example, A/RH2-TT100-O-4X-4 pairs a ±2% RH sensor with a 100 Ohms RTD in a NEMA 4X outside-air enclosure.

Representative configurations include:

• A/RH1-TT100-O-4X-4 — ±1% RH accuracy with a 100 Ohms RTD.
• A/RH3-TT1K-O-4X-4 — ±3% RH accuracy with a 1000 Ohms RTD.
• A/RH2-TTM1K-O-4X-4-POTTED — a matched, NIST-calibrated 1K element with a potted build.