DRETOP EHSW-6500 Precision Temperature- and Humidity-Controlled Weighing System

Overview

The DRETOP EHSW-6500 Precision Temperature- and Humidity-Controlled Weighing System is an engineered environmental chamber specifically designed for gravimetric analysis of particulate matter filters in compliance with national and international ambient air and stack emission monitoring standards. It integrates a high-stability climate-controlled enclosure with precision weighing infrastructure to eliminate thermal and hygroscopic drift during filter mass measurement — a critical requirement for low-concentration particulate mass determination per HJ 836–2017, HJ 656, and GB/T 16157. The system operates on the principle of controlled equilibration: samples (e.g., quartz or PTFE membrane filters) are conditioned at defined temperature and relative humidity for ≥24 hours prior to weighing, ensuring thermodynamic equilibrium between the filter substrate and surrounding atmosphere. This eliminates moisture sorption/desorption artifacts and minimizes static charge accumulation, directly addressing the metrological challenges outlined in ISO/IEC 17025-accredited environmental laboratories.

Key Features

• Optimized dual-path airflow design ensures uniform temperature and humidity distribution (±2 °C / ±2 %RH) while suppressing laminar turbulence near the weighing pan — critical for microgram-level repeatability.
• Stainless steel interior chamber and vibration-isolated external housing decouple mechanical noise from compressors, fans, and cooling circuits, preventing transmission of structural resonance to integrated analytical balances.
• 7-inch color TFT touchscreen controller with real-time graphical display of temperature/humidity trends, historical data logging (time-stamped tabular export via USB), and programmable setpoint profiles.
• Negative-pressure sealed chamber architecture maintains internal isolation during operator access, preventing cross-contamination between samples and ingress of ambient airborne particles (>0.3 µm).
• Independent heating and refrigeration circuits enable rapid stabilization (<30 minutes post-door opening) and consistent operational readiness without thermal overshoot or hysteresis.
• Multi-layer anti-vibration workbench with adjustable leveling feet and optional custom sample fixtures (filter holders, weighing boats, glass vials) supports traceable mass measurement across diverse substrates.
• RS232/USB interfaces compliant with METTLER TOLEDO, SARTORIUS, and OHAUS balance protocols; automatic weight capture, timestamping, and local storage within the chamber’s embedded controller.
• Modular expansion architecture includes standardized I/O ports for robotic arm integration, ionizing de-static modules, auto-sampler carousels, and PLC-based sequencing — enabling full unattended operation under GLP/GMP audit trails.

Sample Compatibility & Compliance

The EHSW-6500 accommodates standard 47 mm and 90 mm diameter filter media (quartz fiber, Teflon®, cellulose ester), Petri dishes, aluminum pans, and volumetric glassware used in EPA Method 201A, HJ 836–2017, and ISO 12103-1 reference dust protocols. Its environmental performance meets calibration verification requirements per GB/T 5170.2–1996 (temperature equipment), GB/T 5170.5–1996 (humidity equipment), and GB/T 2423.3–2016 (IEC 60068-2-78, constant damp heat). Regulatory alignment includes HJ 76–2017 (CEMS QA/QC), HJ/T 397–2007 (stack sampling QA), and JG 1036–2001 (electronic balance verification). All control firmware supports audit-ready event logging required under CNAS-CL01:2018 and ISO/IEC 17025:2017 Clause 7.7.

Software & Data Management

The embedded controller runs deterministic real-time OS with non-volatile memory for ≥12 months of continuous environmental logs (1-min intervals). Data export conforms to CSV and Excel-compatible formats with embedded metadata: chamber ID, operator code, sample ID, equilibration duration, final RH/°C setpoints, and balance serial number. Optional Ethernet connectivity enables remote monitoring via HTTP API and integration into LIMS platforms supporting ASTM E1578 or ISO/IEC 17025-compliant electronic records. Audit trail functionality satisfies FDA 21 CFR Part 11 requirements for electronic signatures, user-level access control, and immutable change history.

Applications

• Gravimetric quantification of PM_2.5, PM₁₀, and low-concentration stack particulates (<20 mg/m³) per HJ 836–2017 and EPA Method 5I.
• Pre- and post-sampling conditioning of filters in ambient air monitoring networks (e.g., national reference sites, urban background stations).
• Method validation and interlaboratory comparison studies requiring strict adherence to ISO 12103-1 and ISO 4406 particle counting standards.
• Research on hygroscopic growth factors of aerosol particles under controlled RH gradients (40–90 %RH).
• QC/QA workflows in third-party environmental testing labs accredited to CNAS, CMA, or ILAC-MRA frameworks.

FAQ

What is the minimum detectable mass change supported by this system?
The detection limit is governed by the connected analytical balance (not the chamber itself); the EHSW-6500 provides environmental stability compatible with 1 µg readability balances when operated within its specified uniformity tolerances.
Does the system support automated calibration of internal sensors?
Yes — built-in sensor self-diagnostic routines verify thermistor and capacitive RH sensor drift against factory calibration curves; NIST-traceable external probes can be used for periodic verification per GB/T 5170.2–1996 Annex B.
Can the chamber operate continuously for 72-hour unattended conditioning cycles?
Yes — rated for continuous duty with redundant safety cutoffs (compressor overheat, fan failure, door-open alarm, and dual-stage temperature limiters) meeting Class II electrical safety per GB 4793.1.
Is the data export format compatible with common LIMS platforms?
CSV and Excel exports include ISO 8601 timestamps, ISO 3166-1 alpha-2 country codes, and SI unit annotations; API endpoints support RESTful GET/POST requests for direct middleware ingestion.
How is electrostatic interference mitigated during weighing?
The chamber incorporates grounded stainless steel surfaces, conductive flooring interface, and optional ionizer port — reducing surface voltage to <±100 V per ANSI/ESD S20.20 guidelines when configured with external neutralization modules.