Transmitter-Strap

Supported Applications

The ACI Strap-On Series is a family of single-point pipe-surface temperature transmitters. Instead of an inserted probe, the sensing element is a 1.5" square copper plate held against the pipe by a clamp, making the series well suited to retrofit applications where an immersion-style sensor cannot be inserted into the pipe or where high accuracy is not required. Each transmitter delivers a two-wire, 4-20 mA loop-powered output, with an optional 3-Wire voltage output of 1-5 VDC or 2-10 VDC, to a building automation system (BAS) or controller.

The clamp-mounted design fits pipe sizes from 1 1/4" (32 mm) to 4" (100 mm). For best thermal contact ACI recommends cleaning the pipe and applying heat transfer paste between the copper plate and the pipe wall. Hose-clamp and heat-transfer-paste accessories are offered to complete the installation.

Operating Conditions & Performance

The sensing element is a platinum RTD with a positive temperature coefficient (PTC) and a single sensing point conforming to DIN EN 60751 (IEC 751), coupled to a Copper sensing plate. It is offered as a 100 Ω nominal (A/TT100, A/TTM100) or 1 KΩ nominal (A/TT1K, A/TTM1K) element referenced at 0°C (32°F), with a tolerance of +/- 0.06% Class A.

Transmitters are powered from an unregulated or regulated +8.5 to 32 VDC supply (reverse-polarity protected) drawing 25 mA minimum. Maximum load resistance tracks the supply: a 250 Ω load needs +13.5 to 32 VDC and a 500 Ω load needs +18.5 to 32 VDC. Output is 4-20 mA (2-Wire, loop powered) current or 1-5 VDC or 2-10 VDC (3-Wires) voltage, landed on polarity-sensitive screw terminal blocks sized for 16 AWG to 26 AWG conductors.

Calibrated accuracy is ±0.2% for temperature spans up to 500°F (260°C) and ±0.5% for spans over 500°F (260°C); temperature drift is ±0.04%/°F for spans under 100°F (38°C) and ±0.02%/°F for spans over 100°F (38°C). The calibrated span is selectable from a minimum of 50°F (28°C) up to a maximum of 300°F (148°C). Transmitters are calibrated at 71°F (22°C) nominal, operate over -40°F to 185°F (-40 to 85°C), store at -40 to 71 °C (-40 to 160 °F), and tolerate 0 to 90% non-condensing humidity.

Configuration Options

The lineup differs first by sensing element: the A/TT100 and matched A/TTM100 use the 100 Ω platinum element, while the A/TT1K and matched A/TTM1K use the 1 KΩ element. Matched TTM parts are supplied with a defined calibrated span and default to a 3-point NIST certificate, upgradeable to a 5-point certificate via the -5PTNIST suffix.

Output type is a second differentiator: current models provide 4-20 mA (2-Wire, loop powered) and voltage models provide 1-5 VDC or 2-10 VDC (3-Wires).

Enclosure choice sets rating, material and temperature limits. The Galvanized Steel -GD is NEMA 1 (IP 10) rated for -40 to 93 °C (-40 to 200 °F); the ABS Plastic -PB is UL94-HB plenum rated for -30 to 85 °C (-22 to 185 °F); and the Polystyrene -4X is UL94-V2, NEMA 4X (IP 66), rated for -40 to 70 °C (-40 to 158 °F).

Key Product Differences

Part numbers follow the pattern A/<SENSOR SERIES>-S-<OUTPUT>-<ENCLOSURE>, assembled from the sensor element, output signal and enclosure, and may specify a calibrated span.

• Element: TT100 / TTM100 (100 Ω) and TT1K / TTM1K (1 KΩ), with matched TTM parts available NIST certified.
• Output signal: 4-20 mA (2-Wire, loop powered) current or 1-5 VDC or 2-10 VDC (3-Wires) voltage.
• Enclosure: Galvanized Steel (-GD), ABS Plastic (-PB) and Polystyrene NEMA 4X (-4X).

Representative catalog part numbers include A/TT100-S-2-GD, A/TT1K-S-4-4X and A/TTM100-S-4-GD. Installation accessories include A/HOSE CLAMP-2-5" and A/HOSE CLAMP-2-12" clamps and NSG heat transfer paste; matched TTM parts add the -5PTNIST 5 Point Calibration and Certificate option.