The Greystone Model HAHTOBB218E002 High Accuracy Outside Air Humidity and Temperature Transmitter, engineered and manufactured by Greystone Energy Systems Inc. in Moncton, New Brunswick, Canada, is a premium meteorological-grade sensing instrument designed for high-performance Building Automation Systems (BAS/BMS) and advanced commercial HVAC applications.

Accurate outside air enthalpy measurement is the cornerstone of modern energy-efficient HVAC design. Building automation controllers rely on precise ambient temperature and relative humidity telemetry to compute true outdoor enthalpy. This data determines the exact thermodynamic conditions under which an air-side economizer system can bring in 100% outside air to cool the interior (free cooling), saving significant chiller compressor energy while keeping indoor thermal comfort optimized.

Model Number Code Architecture Breakdown (HAHTOBB218E002):
- HAHT: High Accuracy Humidity / Temperature Transmitter Series.
- OB: Outside Air mounting style, featuring an integrated multi-plate aerodynamic solar radiation and wind shield.
- B: Industrial grey polycarbonate enclosure with a hinged and gasketed cover.
- 2: High-accuracy 2% relative humidity specification across 5% to 95% RH.
- 18: Precision 1000 Ohm Platinum RTD, 2-wire, IEC 751 compliant, 385 temperature coefficient, thin film, Class A.
- E: 0 to 10 VDC dual analog output scaling for both humidity and temperature channels.
- 002: Factory calibrated temperature transmitter range of 0°C to 50°C (32°F to 122°F).

Key Engineering Features & Operational Advantages:
- Precision Thermoset Polymer Capacitive RH Sensor (2% Accuracy): Utilizes an advanced thermoset polymer capacitive sensing element that delivers a calibrated accuracy of ±2% RH. The element offers high chemical resistance, fast recovery from condensation, and long-term stability with minimal annual calibration drift.
- Class A Platinum Pt1000 Thin-Film Temperature Sensor: Incorporates a high-precision 1000 Ohm Platinum RTD conforming to IEC 751 Class A specifications (interchangeability error of only ±0.15°C at 0°C). The internal transmitter circuitry converts the resistance value into a linearized 0 - 10 VDC output proportional to 0°C to 50°C.
- Integrated Multi-Plate Solar Radiation & Wind Shield: The sensing elements are enclosed within an aerodynamic, multi-plate louvred solar radiation shield molded from white UV-reflective thermoplastic. This shield completely blocks solar thermal radiation heating and wind-driven precipitation while promoting unrestricted natural ambient airflow across the sensors.
- Weatherproof IP65 / NEMA 4X Polycarbonate Enclosure (B-Style): The electronic transmitter module is enclosed in a heavy-duty UL94-V0 flame-retardant grey polycarbonate housing sealed with a continuous neoprene perimeter gasket. The hinged cover with a snap-latch mechanism allows rapid access for field wiring without the risk of dropping loose cover screws.
- Dual 0 - 10 VDC Analog Output Architecture: Provides two completely independent 0 - 10 VDC analog outputs (one for 0 - 100% RH and one for 0°C - 50°C temperature), ensuring immediate compatibility with standard commercial DDC controllers and PLC platforms (Honeywell, Johnson Controls, Siemens, Schneider Electric).

Typical Industrial Applications:
- Air-side economizer cycle control and enthalpy optimization for corporate office towers, luxury hotels, and enterprise data centers.
- Cooling tower water basin temperature/humidity optimization and central chiller plant automation.
- Commercial greenhouse environmental monitoring and high-value agricultural climate control.
- Ambient environmental weather stations and industrial facility perimeter air monitoring.

• Manufacturer: Greystone Energy Systems Inc.
• Country of Origin: 100% Canada (Made in Canada)
• Product Line: HAHT Series High Accuracy Humidity & Temperature Transmitters
• Model Designation: HAHTOBB218E002
• Relative Humidity Channel:
  - Sensor Type: Thermoset polymer capacitive sensor
  - Measurement Range: 0 to 100% RH
  - Accuracy: ±2% RH over 5% to 95% RH span
  - Hysteresis: ±1.5% RH maximum
  - Response Time: 15 seconds typical (for 63% step change @ 25°C in slow-moving air)
  - Long-Term Stability: < ±1.2% RH drift over 5 years
• Temperature Channel:
  - Sensor Element: 1000 Ohm Platinum RTD (Pt1000)
  - Wiring Configuration: 2-wire
  - Standard Compliance: IEC 751, 385 alpha temperature coefficient, Thin Film
  - RTD Accuracy Class: Class A (±0.15°C @ 0°C)
  - Transmitter Scaled Range: 0°C to 50°C (32°F to 122°F)
  - Transmitter Electronics Accuracy: ±0.1°C of calibrated span
• Analog Output Signals:
  - Humidity Output: 0 - 10 VDC linear (representing 0 - 100% RH)
  - Temperature Output: 0 - 10 VDC linear (representing 0°C to 50°C)
• Minimum Output Load Resistance: 10,000 Ω (10 kΩ)
• Power Supply Requirements: 18 to 30 VDC or 15 to 26 VAC (half-wave rectified)
• Current Consumption: Current draw: 22 mA maximum @ 24 VDC; 50 mA maximum @ 24 VAC
• Sensor Protection: Multi-plate white UV-resistant solar radiation and wind shield
• Probe Tip Filter: Sintered porous filter protecting sensor element from dust and airborne particulates
• Enclosure Construction: Grey Polycarbonate, UL94-V0 flame retardant, hinged cover with latch and neoprene perimeter gasket
• Ingress Protection Rating: IP65 / NEMA 4X (sealed against driving rain, dust, and washdown spray)
• Conduit / Cable Entry: Knockout with supplied liquid-tight cable gland fitting
• Wiring Terminations: Screw terminal blocks accommodating 14 to 22 AWG conductors
• Operating Ambient Temperature: -40°C to +60°C (-40°F to +140°F)
• Operating Ambient Humidity: 0% to 100% RH (condensing environments permitted outside shield)
• Quality & Safety Approvals: CE marked, RoHS compliant, ISO 9001 certified manufacturing
• Net Instrument Weight: Approximately 450 g (1.0 lb).