RainWise RH/T Thermo-Hygrometer Sensor

Overview

The RainWise RH/T Thermo-Hygrometer Sensor is a precision environmental monitoring instrument engineered for long-term stability, high reproducibility, and field-deployable reliability in meteorological, industrial hygiene, HVAC validation, and environmental research applications. Designed around dual-sensor architecture—comprising an integrated solid-state temperature transducer with on-board signal conditioning and a polymer-film capacitive relative humidity sensing element—the RH/T operates on well-established physical principles: resistance-based thermal measurement (via user-selectable RTD, thermistor, or thermocouple configurations) and dielectric constant variation detection in hygroscopic polymer films for RH quantification. Its compact, weather-resistant housing is mounted within a naturally aspirated, ISO 7726-compliant radiation shield (standard white-painted aluminum louvre enclosure), minimizing solar loading and convective bias while ensuring representative ambient air sampling. All RH/T units are supplied with NIST-traceable calibration documentation, supporting compliance with ISO/IEC 17025 laboratory accreditation requirements and GLP/GMP data integrity expectations.

Key Features

• Integrated signal-conditioning circuitry with built-in operational amplifier ensures stable analog output across variable cable lengths (up to 300 m) and electromagnetic interference-prone environments.
• Polymer-film capacitive RH sensor housed behind a sintered hydrophobic PTFE filter, providing particulate and condensation protection without compromising response time (t₉₀ < 15 s at 1 m/s airflow).
• Multiple temperature sensing options: platinum RTD (Pt100 or Pt1000), NTC thermistor (e.g., 10 kΩ @ 25 °C), or Type E/K thermocouple—field-configurable to match system integration needs.
• Wide operational envelope: functional from −40 °C to +85 °C ambient, with calibrated performance specified from −40 °C to +65 °C for temperature and 0–100% RH across the full range.
• Dual-output capability: selectable RS-232 serial interface (ASCII protocol, configurable baud rate) or analog outputs (0–5 VDC, 0–10 VDC, or 4–20 mA) for direct integration into SCADA, DAQ, or BMS platforms.
• Modular mechanical design enables rapid mounting onto RainWise Monopod masts or third-party 1″–1.5″ OD pole systems using standard U-bolt hardware.

Sample Compatibility & Compliance

The RH/T sensor is intended for continuous measurement of ambient atmospheric air in outdoor and semi-conditioned indoor environments. It is not designed for use in corrosive, explosive, or high-particulate gas streams without supplemental filtration or enclosure. The device complies with IEC 60529 IP65 ingress protection specifications when installed with its standard radiation shield. Its calibration methodology adheres to ASTM E2234 (Standard Practice for Calibration of Hygrometers) and supports traceability to NIST SRM 2365 (Relative Humidity Standard Generator). For regulated environments—including pharmaceutical cleanrooms, environmental chambers, and climate-controlled storage facilities—the RH/T meets foundational requirements for data integrity under FDA 21 CFR Part 11 when paired with compliant data acquisition software featuring audit trail, electronic signature, and change control functionality.

Software & Data Management

While the RH/T operates as a standalone analog/digital sensor, it is fully compatible with RainWise’s proprietary WeatherLink platform and third-party systems supporting Modbus RTU, SDI-12, or ASCII serial protocols. When deployed in networked configurations, time-stamped measurements (temperature and RH) can be logged at user-defined intervals (1 s to 24 h), with optional linearization and dew point calculation performed either onboard (in RS-232 mode with firmware v2.1+) or externally. Raw output values retain native resolution (0.1 °C / 0.1% RH), enabling post-acquisition uncertainty propagation per GUM (JCGM 100:2008). All calibration certificates include measurement uncertainty budgets referenced to NIST standards, facilitating ISO 17025 internal audit readiness.

Applications

• Meteorological networks requiring long-term, low-drift environmental baselines (e.g., NOAA COOP, USCRN, ECA&D)
• HVAC system commissioning and seasonal performance verification per ASHRAE Guideline 1
• Pharmaceutical warehouse and stability chamber monitoring per ICH Q1A(R2) and EU Annex 15
• Agricultural microclimate studies, including greenhouse and post-harvest storage profiling
• Indoor air quality (IAQ) assessment in schools, offices, and healthcare facilities per ASHRAE Standard 62.1
• Environmental stress testing of materials and electronics per MIL-STD-810 and IEC 60068-2 series

FAQ

Is the RH/T sensor suitable for use inside enclosed chambers or ducts?
Yes—when installed with appropriate mounting adapters and airflow management (minimum 1 m/s recommended), though the standard radiation shield should be omitted indoors.
Does the RH/T require periodic recalibration?
Annual recalibration is recommended for applications governed by ISO/IEC 17025 or GxP; field verification using saturated salt solutions may be performed quarterly.
Can the analog output be used with data loggers lacking excitation voltage?
Yes—the integrated op-amp provides active voltage output; no external excitation is required for 0–5 V or 0–10 V modes.
What is the typical drift specification over two years?
Under normal outdoor exposure, RH drift is ≤±0.8% RH/year; temperature drift is ≤±0.05 °C/year (based on accelerated aging tests per IEC 60751 Annex D).
Is firmware update capability available?
Firmware updates are supported via RS-232 connection using RainWise-provided utilities; version history and release notes are documented in the Technical Reference Manual v4.3+.