YiHeng LHS Series Temperature and Humidity Controlled Chamber – Balanced Control Architecture

Overview

The YiHeng LHS Series Temperature and Humidity Controlled Chambers are engineered for precise, long-term environmental simulation in laboratory and quality assurance settings. These upright chambers implement TMHM (Temperature–Humidity Hybrid Modulation), a balanced control architecture that dynamically coordinates refrigeration, heating, and steam/humidification subsystems to minimize thermal lag and humidity overshoot. Unlike conventional on-off or PID-only systems, TMHM continuously adjusts actuator duty cycles—compressor speed, heater power, and humidifier output—based on real-time feedback from dual high-stability platinum resistance thermometers (PT100) and capacitive RH sensors. This closed-loop strategy ensures stable chamber conditions even during frequent door openings or load changes, making the LHS series suitable for stability testing per ICH Q1A(R2), accelerated aging per ASTM D4332, and material conditioning per ISO 291. The chamber operates within a nominal ambient range of 15–30°C and requires no external water supply when equipped with integrated reservoir-based humidification.

Key Features

• Mirror-polished 304 stainless steel interior with fully radiused corners and seamless welds—compliant with ISO 14644-1 Class 7 cleanroom surface requirements for low particle shedding and ease of disinfection.
• Stepless vertical shelf positioning system with corrosion-resistant anodized aluminum supports—enabling flexible sample arrangement without tools and supporting up to 15 kg per shelf (uniformly distributed).
• Imported industrial-grade microcontroller with 0.1°C/0.1% RH resolution, 128×64 graphic LCD interface, and configurable alarm thresholds for temperature, humidity, and sensor fault conditions.
• Dual-stage safety architecture: primary control loop with adaptive tuning plus independent mechanical over-temperature limiter (settable between 50–100°C) that physically interrupts power to heating elements upon threshold breach.
• Zero-ozone R134a refrigerant system with copper-aluminum finned evaporator and high-efficiency scroll compressor—designed for continuous operation at 85°C/95% RH without condensate accumulation or coil icing.

Sample Compatibility & Compliance

The LHS series accommodates standard ISO/IEC 17025-accredited test loads—including pharmaceutical packaging, polymer films, electronic assemblies, and biological reference standards—within its working volume (dimensions available in manufacturer’s dimensional specification sheet). Internal airflow is optimized via rear-mounted axial fans and perforated top/bottom baffles to maintain ≤±1.0°C temperature uniformity and ≤±3% RH deviation across the workspace, verified per IEC 60068-3-5. The chamber meets CE marking requirements under Directive 2014/30/EU (EMC) and 2014/35/EU (LVD), and its control firmware supports audit-ready event logging required for GLP and GMP environments. Optional calibration certificates traceable to NIM (National Institute of Metrology, China) are available upon request.

Software & Data Management

An optional RS485/Modbus RTU interface enables integration with centralized lab monitoring systems (e.g., LabVantage, Siemens Desigo CC). The embedded controller logs timestamped temperature and humidity values at user-defined intervals (1–60 minutes), storing up to 30 days of data internally. Export is supported via USB flash drive in CSV format—with column headers compliant with ASTM E2500-18 Annex A2 for raw environmental data archiving. All logged events—including door openings, alarm triggers, and setpoint changes—are time-stamped and non-erasable, satisfying FDA 21 CFR Part 11 requirements for electronic records when used with validated third-party software.

Applications

• Pharmaceutical stability studies (ICH Q5C): long-term storage at 25°C/60% RH and accelerated conditions (40°C/75% RH).
• Polymer hygroscopic conditioning prior to tensile or impact testing per ISO 527 and ASTM D638.
• Electronics reliability screening: moisture soak per JESD22-A110 and thermal cycling per JEDEC J-STD-020.
• Adhesive and coating curing validation under controlled humidity to assess crosslinking kinetics.
• Reference material equilibration for gravimetric moisture analysis (ASTM D4442) and Karl Fischer titration.

FAQ

What is TMHM balanced control, and how does it differ from standard PID regulation?

TMHM integrates coupled thermal and moisture mass-transfer models into the control algorithm, allowing simultaneous optimization of cooling, heating, and humidification outputs—reducing recovery time after disturbance by up to 40% compared to sequential PID loops.
Is the chamber suitable for use with volatile organic solvents?

No. The LHS series is not explosion-proof and lacks intrinsically safe components; it is intended for non-hazardous, non-corrosive atmospheres only.
Can humidity be maintained below 45% RH?

Not natively. The standard configuration achieves minimum 45% RH; for lower ranges, a desiccant-based dry air purge option must be specified at time of order.
Does the system support remote monitoring via Ethernet or Wi-Fi?

Ethernet and Wi-Fi connectivity are not built-in but can be added via certified third-party gateway modules compatible with Modbus TCP.
What calibration documentation is included with shipment?

Each unit ships with a factory verification report covering temperature uniformity, humidity accuracy, and alarm response—traceable to national standards via internal metrology procedures.