Transmitter-Rigid-Averaging

Supported Applications

The ACI Rigid Averaging Transmitter Series uses a continuous sensing element that reports a better average temperature over the full probe length than a single-point sensor. The rigid probes are designed to be installed in small to medium size ducts and feed 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 an electronic controller or building automation system in HVAC applications.

The probe is mounted by drilling a 3/8" hole in the duct and inserting it until the foam pad is tight to the duct wall, using a 1/8"-27 NPSM process connection. All transmitters include Zero and Span adjustments for field calibration and are factory calibrated. The 304 Stainless Steel probe and choice of enclosures let the same unit average supply, return or mixed-air temperature across a duct cross-section.

Operating Conditions & Performance

The sensing element is a platinum RTD with a positive temperature coefficient (PTC) and a Continuous sensing profile conforming to DIN EN 60751 (IEC 751), referenced at 1 KΩ nominal at 0°C (32°F). Sensor accuracy is +/- 0.1% at 0°C (32°F), +/- 0.25% at 21°C (70°F) and +/- 1.0% at 130°C (266°F), and response time is 15 Seconds nominal at a 63% step change. The sensor operating range is -40 to 135 °C (-40 to 275 °F).

Transmitters are powered from +8.5 to 32 VDC (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 under 500°F (260°C); temperature drift is +/- 0.04%/°F for spans under 100°F (38°C) and +/- 0.02% 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 400°F (204°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 80 °C (-40 to 176 °F), and tolerate 0 to 90% non-condensing humidity.

Configuration Options

All Rigid Averaging models share the same continuous 1 KΩ platinum element and differ principally by probe length, output type, calibration and enclosure. The standard TT1K and the matched TTM1K are the two element grades; the matched TTM1K is supplied with a defined calibrated span and NIST certification. Its default certificate is a 3 Point NIST at 20%, 50% and 80% of span, upgradeable to a 5 Point NIST at 20%, 35%, 50%, 65% and 80% of span.

Rigid probe insertion length is selectable at 12", 18", 24" or 36" to match duct width, with each probe using a 0.250" (6.35mm) 304 Stainless Steel sheath. Output type is either 4-20 mA (2-Wire loop powered) current or 1-5 VDC or 2-10 VDC (3-Wires) voltage.

Enclosure choice sets rating, material and temperature limits. The Galvanized Steel -GD is NEMA 1 (IP10) rated for -40 to 115 °C (-40 to 239 °F); the ABS Plastic -PB is UL94-HB plenum rated for -30 to 90 °C (-22 to 194 °F); the Aluminum bell-box -BB is NEMA 3R (IP 14); and the Polystyrene -4X is UL94-V2, NEMA 4X (IP 66).

Key Product Differences

Part numbers follow the pattern A/TT1K-RA-xx"-x-yy, where A/ is the sensor series, TT1K the model series, RA the averaging configuration, xx" the probe length, x the output signal and yy the enclosure.

• Element grade: standard TT1K or matched TTM1K (defined calibrated span, NIST certified).
• Probe length: 12", 18", 24" and 36" rigid averaging probes.
• Output signal: 4-20 mA (2-Wire loop powered) current or 1-5 VDC or 2-10 VDC (3-Wires) voltage.
• Enclosure: ABS Plastic (-PB), Galvanized Steel (-GD), Aluminum bell box (-BB) and Polystyrene NEMA 4X (-4X).

Representative catalog part numbers include A/TT1K-RA-24"-4-PB, A/TTM1K-RA-18"-4-GD and A/TT1K-RA-36"-4-4X. Matched TTM1K parts default to a 3 point NIST certificate; a 5 point certificate can be specified by adding -5PTNIST to the end of any TTM part number.