RH-200 Relative Humidity Generator

Overview

The RH-200 Relative Humidity Generator is a benchtop, fully computer-controlled environmental conditioning system engineered for precision generation and delivery of stable, traceable humidity levels within controlled gas streams. Based on the dual-mass-flow mixing principle—where dry carrier gas (air or nitrogen) and saturated wet gas are dynamically blended under real-time feedback—the RH-200 achieves high reproducibility in relative humidity output across its full operational range (3–95% RH). Its core measurement architecture integrates a secondary chilled-mirror dew point analyzer, providing independent, NIST-traceable verification of humidity setpoints and enabling closed-loop correction. Designed explicitly for integration into analytical workflows, the RH-200 delivers a constant, laminar flow (standard 500 mL/min; optional 5 L/min) with minimal thermal and vapor-phase perturbation—making it suitable for coupling with sensitive instruments including differential scanning calorimeters (DSC), thermogravimetric analyzers (TGA), dynamic mechanical analyzers (DMA), X-ray diffractometers (XRD), gas chromatographs (GC), gloveboxes, and controlled-atmosphere dryers. First introduced by VTI Instruments in 1994 as the second-generation successor to its predecessor, the RH-200 incorporates enhanced hardware stability, improved thermal management, and a robust Windows-based graphical user interface supporting automated method sequencing and audit-ready data logging.

Key Features

• Fully automated, software-driven operation with intuitive GUI for defining multi-step RH and temperature profiles
• Dual mass flow controllers (MFCs) for precise, independent regulation of dry and saturated gas streams
• Integrated secondary chilled-mirror dew point analyzer for continuous, high-fidelity RH validation and closed-loop stabilization
• Thermostatically controlled chamber (ambient to 50 °C) ensuring consistent saturation temperature and minimizing condensation risk downstream
• Standard 500 mL/min flow rate with optional high-flow configuration (up to 5 L/min) for large-volume enclosures or rapid equilibration
• Optional heated transfer line (1–2 m length) featuring integrated PID temperature control, thermocouple feedback, and uniform thermal profiling to prevent dew formation in delivery tubing
• Optional remote RH/T sensor with analog/digital output, enabling real-time monitoring at the sample zone of connected instrumentation
• Compliant with GLP/GMP documentation requirements: full timestamped event logging, user-access controls, and electronic signature support via native software

Sample Compatibility & Compliance

The RH-200 is designed for compatibility with a broad spectrum of analytical platforms requiring controlled hygrothermal environments—including but not limited to ASTM E104 (Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions), ISO 18877 (Soil quality — Determination of water-soluble anions), and USP (Pharmaceutical Dosage Forms). Its modular architecture allows seamless interfacing with instruments operating under inert atmospheres (e.g., nitrogen-purged gloveboxes) or vacuum-compatible configurations (with optional pressure-compensated MFCs). All firmware and software comply with FDA 21 CFR Part 11 requirements for electronic records and signatures, including audit trails, role-based access, and non-erasable data archiving. The system supports IQ/OQ documentation packages and is routinely deployed in regulated QC laboratories performing stability testing, material hygroscopicity assessment, and moisture sorption isotherm characterization per ICH Q5C guidelines.

Software & Data Management

The RH-200 is operated via proprietary Windows-native software featuring a responsive graphical interface with drag-and-drop method builder, real-time trend visualization, and synchronized multi-parameter logging (RH %, temperature, dew point, flow rates, valve status, and error flags). Data export is supported in CSV, XML, and PDF formats—with embedded metadata compliant with FAIR principles (Findable, Accessible, Interoperable, Reusable). The software includes built-in calibration scheduling, automatic drift compensation alerts, and configurable alarm thresholds with email/SNMP notification. All session logs include digital signatures, operator ID, instrument serial number, and firmware revision—ensuring full traceability for regulatory submissions and internal quality audits. Remote monitoring and control are supported over Ethernet (TCP/IP), with optional OPC UA server integration for enterprise-level LIMS/SCADA connectivity.

Applications

• Hygroscopicity and moisture sorption isotherm studies of pharmaceutical excipients, polymers, and battery electrode materials
• In situ environmental conditioning during thermal analysis (TGA, DSC, DMA) to evaluate humidity-dependent decomposition, glass transition, or viscoelastic behavior
• Controlled-humidity aging of electronic components and packaging materials per IPC-TM-650 standards
• Calibration and verification of standalone hygrometers, dew point meters, and climate chamber sensors
• Stability testing of catalysts, MOFs, and desiccants under programmable RH cycling protocols
• Conditioning of samples prior to XRD, FTIR, or Raman analysis to isolate structural changes induced by water uptake
• Humidity-controlled operation of gloveboxes and anaerobic chambers for biological or electrochemical experimentation

FAQ

What carrier gases are compatible with the RH-200?
Dry air and nitrogen are the standard and validated carrier gases. Other inert gases (e.g., argon) may be used subject to MFC calibration verification and compatibility with internal wet-gas saturation components.
Is the RH-200 suitable for use with vacuum-based instruments?
Yes—when equipped with optional pressure-compensated mass flow controllers and configured with back-pressure regulation, the RH-200 can deliver conditioned gas into evacuated systems such as low-pressure TGA or surface science chambers.
How is RH accuracy verified and maintained over time?
The integrated secondary chilled-mirror dew point analyzer provides continuous, traceable verification. Users perform routine calibration using NIST-traceable saturated salt solutions or certified dew point generators, with software-guided procedures and certificate generation.
Can the RH-200 operate unattended for extended periods?
Yes—its embedded controller supports 24/7 operation with watchdog timers, automatic fault recovery, and configurable shutdown protocols. All events and deviations are logged with timestamps and severity tagging.
Does the system support external triggering or synchronization with other instruments?
Yes—digital I/O ports (TTL) and Ethernet-based API (RESTful JSON) enable hardware-level triggering and bidirectional communication with third-party instruments for synchronized environmental ramping and data acquisition.