The ACI Transmitter Outside Air Series pairs a Class A platinum RTD with an onboard temperature transmitter so the outdoor reading arrives at the controller as a scaled analog signal instead of a raw resistance. The 4-20 mA version is two-wire loop powered; the 1-5 VDC and 2-10 VDC versions are three-wire. Zero and span potentiometers allow field recalibration against NIST-certified reference equipment, and every unit ships in a weatherproof enclosure with 1/2 in knockouts or 1/2 in NPT threaded hubs for installation.
Specifications sourced from the ACI Transmitter Outside Air Data Sheet and ACI Outside Air Series Temperature Transmitter Installation & Operation Instructions (Version 2.0). Verified against ACI source documentation on 26 August 2026.
Best For
- Outside Air Temperature Sensing
- Economizer Control
- Cold Storage Facilities and Warehouses
- High Moisture Environments
Calibrated span is built to order. Specify the low and high temperature span in F or C on your purchase order. Minimum span 50 F (28 C), maximum span 300 F (148 C); ACI notes best accuracy in 100 F increments.
Key Features
Single-Point Outdoor Assembly
One platinum RTD sensing point paired with the transmitter board, supplied in a weatherproof enclosure with 1/2 in knockouts or 1/2 in NPT threaded hubs.
Euro Enclosure
PC/ASA Plastic with UV Protectant, rated Weatherproof (no NEMA/IP rating published), with an enclosure operating range of -40 to 88 C (-40 to 190 F).
Scaled Analog Output
4-20 mA Output, two-wire, loop powered, so the controller sees a linear signal rather than a raw resistance curve.
Field Recalibration
Onboard zero and span potentiometers allow adjustment against NIST-certified reference equipment. ACI also offers factory recalibration on returned transmitters.
Class A Platinum Element
+/-0.06% Class A RTD to DIN EN 60751 (IEC 751), 3850 ppm/C, for repeatable outdoor measurement across the calibrated span.
Matched and NIST Certified
Supplied as ACI's matched RTD configuration with a 3-point NIST Certificate included by default on TTM part numbers.
Technical Specifications
| Output Signal | Wiring | 4-20 mA Output | Two-wire, loop powered |
|---|---|
| Transmitter Supply Voltage | Supply Current | +8.5 to 32 VDC (reverse polarity protected) | 25 mA minimum |
| Minimum Supply Voltage for This Output | +8.5 to 32 VDC |
| Maximum Load Resistance | (Terminal Voltage - 8.5 V) / 0.020 A |
| Calibrated Accuracy | Linearity | Temperature spans below 500 F (260 C): +/-0.2%. Calibrated at 71 F (22 C) nominal |
| Thermal Drift | Spans below 100 F (38 C): +/-0.04%/F | Spans above 100 F (38 C): +/-0.02%/F |
| Minimum | Maximum Calibrated Temperature Span | 50 F (28 C) | 300 F (148 C) |
| Warm Up Time | Warm Up Drift | 10 minutes | +/-0.1% |
| Transmitter Operating Temperature Range | -40 to 185 F (-40 to 85 C) |
| Zero and Span Adjustment | Onboard potentiometers for field recalibration |
| Connections | Wire Size | Screw terminal blocks (polarity sensitive) | 16 AWG (1.31 mm2) to 26 AWG (0.129 mm2) |
| Terminal Block Torque Rating | 0.37 ft-lb (0.5 Nm) nominal |
| Sensor Type | Sensor Curve | Sensing Points | Platinum RTD | PTC (Positive Temperature Coefficient) | One |
| Sensor Resistance | Lead Wire Colors | 100 Ohms nominal at 0 C (32 F) | Brown/Brown |
| RTD Tolerance Class | Sensor Accuracy | +/-0.06% Class A. Tolerance formula: +/- C = 0.15 C + (0.002 x |t|), where |t| is the absolute temperature above or below 0 C in C |
| Sensor DIN Standard | Temperature Coefficient | DIN EN 60751 (IEC 751) | 3850 ppm/C |
| Sensor Response Time (63% Step Change) | 8 seconds nominal (I0000857 v2.0 installation instructions; not stated in the data sheet) |
| NIST Certification Points | 3-point NIST at 20%, 50% and 80% of span (default) | 5-point NIST at 20%, 35%, 50%, 65% and 80% of span, ordered separately as NIST TTM CERT-5PT. |
| Operating | Storage Temperature Range | -40 to 71 C (-40 to 160 F) |
| Sensor Operating Humidity Range | 0 to 100% RH (data sheet) |
| Transmitter Operating Humidity Range | 0 to 90% RH, non-condensing (I0000857 v2.0 installation instructions) |
| Lead Length | Conductor Size | 14 in (35.6 cm) | 22 AWG (0.65 mm) |
| Lead Wire Insulation | Wire Rating | Etched Teflon (PTFE) colored leads | MIL-W-16878/4 (Type E) |
| Conductor Material | Silver plated copper |
| Cord Grip Fitting Material | Flammability | Polyamide 6.6 | UL94-V2 (included with the -4X enclosure option only) |
| Cord Grip Seal Material | NEMA / IP Rating | Neoprene | IP68 (NEMA 4X) |
| Cord Grip Torque Recommendation | 1.83 ft-lbs (2.50 Nm) |
| Enclosure Material | PC/ASA Plastic with UV Protectant |
| Enclosure Operating Temperature Range | -40 to 88 C (-40 to 190 F) |
| Enclosure Flammability Rating | UL94-V0 |
| Enclosure NEMA / IP Rating | Weatherproof (no NEMA/IP rating published) |
| Product Dimensions | See dimensional drawing on the back page of the data sheet |
| Product Weight | 0.49 lbs (0.222 kg) |
| Agency Approvals | RoHS2, WEEE |
Documentation
ACI Transmitter Outside Air Data Sheet- ACI Outside Air Series Temperature Transmitter Installation & Operation Instructions (Version 2.0)
Related Products
- ACI A/TTM100-O-4-BB : Outside Air Temperature Transmitter, Matched 100 Ohm Platinum RTD, 4-20 mA Output, Aluminum NEMA 3R Enclosure, 3-Point NIST Certificate
- ACI A/TTM100-O-4-4X : Outside Air Temperature Transmitter, Matched 100 Ohm Platinum RTD, 4-20 mA Output, Plastic NEMA 4X Enclosure, 3-Point NIST Certificate
Frequently Asked Questions
What temperature span does the A/TTM100-O-4-EH ship with?
The calibrated span is specified at the time of order and is not a stock attribute. The minimum span is 50 F (28 C) and the maximum span is 300 F (148 C); ACI notes best accuracy is achieved in 100 F increments. Provide the required low and high span values with your purchase order.
What supply voltage does the A/TTM100-O-4-EH need?
The transmitter accepts +8.5 to 32 VDC and is reverse polarity protected, drawing 25 mA minimum. For this 4-20 mA Output version the practical minimum is +8.5 to 32 VDC. ACI transmitters do not accept an AC input.
What does the TTM designation mean?
TTM part numbers are ACI's matched RTD configuration and carry a 3-point NIST Certificate by default. Five-point certification is available under part number NIST TTM CERT-5PT. ACI does not define the matching process further in the Outside Air transmitter data sheet.
Where should the A/TTM100-O-4-EH be mounted?
Mount it in shade on the north side of the structure (south side in the southern hemisphere), 1 to 2 ft (0.3 to 0.6 m) below the eave and at least 4 ft (1.22 m) above grade. The sensing tube must point downward so water, ice and debris cannot settle inside it. Avoid chimney walls, vents, doors, dampers and locations above windows.
What is the Euro enclosure rated for?
The Plastic Euro Enclosure is PC/ASA Plastic with UV Protectant, rated Weatherproof (no NEMA/IP rating published), with an enclosure operating range of -40 to 88 C (-40 to 190 F).
ACI Five (5) Year Limited Warranty. This series is covered by ACI's Five (5) Year Limited Warranty. ACI publishes the full warranty terms in the front of the ACI Sensors & Transmitters catalog and on workaci.com; refer to that document for the scope of coverage.
ACI offers recalibration service for transmitters returned to the factory, for a nominal fee.
- Sensor Type:
- Outside Air
- Output Signal:
- 4-20 mA
- CO2 Element:
- None
- Humidity Element:
- None
- VOC Element:
- None
- Temperature Element:
- 100 Ohm Platinum RTD
- Display:
- None
- Supported Protocols:
- None
- Enclosure:
- Plastic Euro
- NIST Certificate:
- Yes
