HUANKONG GHK-7000Z Electronic Soap Film Flowmeter

Overview

The HUANKONG GHK-7000Z Electronic Soap Film Flowmeter is a precision primary standard instrument engineered for traceable volumetric flow calibration of low-to-moderate gas flow rates (typically 1–5000 mL/min). It operates on the soap film displacement principle—a gravimetric time-of-flight method where a calibrated soap film traverses a transparent, temperature-stabilized vertical tube of known internal diameter. The elapsed transit time between two optically defined reference points is measured via high-speed infrared photogates, enabling direct calculation of volumetric flow rate under defined thermobaric conditions. Unlike thermal or differential pressure-based flowmeters, the GHK-7000Z delivers intrinsic accuracy without reliance on gas-specific calibration curves or dynamic compensation models. Its design conforms to JJG 586–2006, the national metrological verification regulation governing soap film flowmeters in China, and supports traceability to national standards through documented uncertainty budgets per ISO/IEC 17025 requirements.

Key Features

• Modular architecture: Interchangeable soap film tubes with distinct inner diameters enable seamless switching among low-, medium-, and high-flow ranges—eliminating cross-range interpolation errors.
• Optical integrity: Light-shielded borosilicate glass tubes minimize ambient light interference and thermal drift; surface-treated inner walls ensure consistent film formation and rupture-free travel.
• High-temporal-resolution timing: Infrared sensing system achieves ±0.001 s time measurement resolution, directly contributing to sub-0.5% relative expanded uncertainty (k=2) in flow rate determination.
• Real-time environmental correction: Integrated temperature and pressure sensors feed into NIST-traceable algorithms that convert measured volume to standardized conditions—either at 273.15 K / 101.325 kPa (STP) or 293.15 K / 101.325 kPa (NTP)—per ISO 10780 and EPA Method 4.
• Embedded data governance: Onboard memory stores ≥1000 calibration records with timestamps, operator IDs, and environmental metadata; USB export enables secure transfer to LIMS or audit-ready spreadsheets.
• Field-deployable power system: Rechargeable lithium-ion battery sustains continuous operation for ≥8 hours; auto-switching AC/DC input ensures uninterrupted use during laboratory validation or mobile environmental monitoring campaigns.

Sample Compatibility & Compliance

The GHK-7000Z is validated for use with dry, non-corrosive, particle-free gases—including ambient air, nitrogen, helium, and synthetic air—across sampling applications compliant with ISO 16000-22 (indoor air), ISO 7708 (aerosol inhalation), EN 12341 (PM₁₀/PM_2.5 monitoring), and OSHA Method ID-121 (airborne contaminants). It meets metrological requirements for Class II calibration devices per JJG 586–2006 and serves as a reference standard in GLP-regulated laboratories performing instrument qualification per ICH Q2(R2). While not intrinsically safe for explosive atmospheres, it is routinely deployed in certified cleanrooms, stack testing vans, and accredited environmental testing facilities.

Software & Data Management

The device runs a deterministic real-time operating system (RTOS) with no external dependencies. All measurements are timestamped using an onboard RTC synchronized to UTC via optional NTP over USB Ethernet adapter. Data files follow CSV format with UTF-8 encoding and include columns for raw transit time, ambient T/P, corrected volume, uncertainty components (time, geometry, thermal expansion), and user-defined sample ID. Audit trail functionality logs all configuration changes, firmware updates, and calibration events—supporting FDA 21 CFR Part 11 compliance when paired with controlled electronic signatures. Optional Bluetooth thermal printers generate tamper-evident paper records with QR-coded traceability links.

Applications

• Primary calibration of personal and stationary air sampling pumps used in occupational hygiene (NIOSH/OSHA protocols).
• Verification of mass flow controllers (MFCs) and rotameters in GC carrier gas lines prior to method validation.
• Field validation of low-flow passive samplers and diffusion badges per ISO 16017-1.
• Uncertainty budgeting for ISO/IEC 17025-accredited testing laboratories conducting particulate matter or VOC analysis.
• Teaching metrology principles—including gas law application, uncertainty propagation, and primary vs. secondary standards—in university analytical chemistry labs.

FAQ

What gases can be calibrated using the GHK-7000Z?

Dry, non-reactive gases such as air, N₂, He, Ar, and CO₂ (at concentrations ≤5%) are suitable. Condensable or corrosive gases (e.g., NH₃, Cl₂, H₂S) must be avoided to preserve optical path integrity and sensor longevity.
Does the GHK-7000Z require annual recalibration?

Per JJG 586–2006, verification frequency depends on usage intensity and criticality; most accredited labs perform semi-annual checks against a national standard. Geometry verification (tube ID measurement) and timing system validation are recommended before each major campaign.
Can the GHK-7000Z operate in high-humidity environments?

Yes—provided inlet gas is filtered to remove aerosols and condensate. Humidity does not affect soap film velocity if dew point remains below ambient temperature; however, >80% RH may increase film rupture risk and necessitate more frequent solution replacement.
Is firmware upgrade supported in the field?

Yes—via USB-connected PC using manufacturer-provided signed firmware packages. Each update includes version-stamped changelog and cryptographic signature verification to maintain regulatory compliance.
How is measurement uncertainty quantified?

According to GUM (JCGM 100:2008), contributors include time measurement (±0.001 s), tube bore diameter (±0.5 µm via coordinate measuring machine), thermal expansion coefficient (glass + gas), and pressure/temperature sensor accuracy (±0.1 °C, ±0.1 kPa). Typical combined standard uncertainty is 0.32% (k=1) at mid-range flows.