Assemblad OPA-105.LCD Benchtop Opacity Meter

Overview

The Assemblad OPA-105.LCD Benchtop Opacity Meter is a precision-engineered instrument designed for quantitative assessment of light attenuation in diesel exhaust smoke, expressed as opacity (%), and its fundamental physical correlate — the specific extinction coefficient k (m⁻¹). Based on the Beer–Lambert law, the device measures the ratio of incident to transmitted radiant flux across a standardized 240 mm optical path, using a reflective photoelectric cell architecture that ensures stable signal acquisition under variable thermal and particulate-loading conditions. Unlike filter-based or scattering-based methods, this absorption-based approach delivers direct traceability to international regulatory definitions of smoke density, particularly those codified in EEC Directive 72/306/EEC for type-approval and in-service testing of compression-ignition engines. The unit integrates active thermal management — maintaining photodetector housing at a constant ≥70 °C — to suppress condensation-induced measurement artifacts and ensure long-term baseline stability. Its dual-mode output (k-value and % opacity) supports both legacy reporting requirements and modern emission modeling workflows requiring physically meaningful extinction coefficients.

Key Features

• Microprocessor-controlled heating system with thermostatic stabilization ≥70 °C for optical components, minimizing dew formation and thermal drift
• Automated zero calibration and span verification routines, reducing operator dependency and improving inter-laboratory reproducibility
• Integrated RS-232 serial interface for real-time data streaming to host PCs or automated test benches
• Dual-parameter display: simultaneous readout of opacity (%) with 0.1% resolution and specific extinction coefficient k (m⁻¹) with 0.01 m⁻¹ resolution
• Dedicated rpm counter input for synchronized engine speed correlation during transient smoke profiling
• Hybrid power architecture: internal 7.2 Ah rechargeable battery (12 V DC) plus universal 220 V AC adapter, enabling flexible deployment in workshop, chassis dyno, or roadside inspection settings
• Compact benchtop form factor (290 × 198 × 175 mm) with robust aluminum housing optimized for vibration resistance and thermal inertia

Sample Compatibility & Compliance

The OPA-105.LCD is validated for use with undiluted raw diesel exhaust gas streams from light- and heavy-duty vehicles, stationary generators, marine auxiliary engines, and non-road mobile machinery. It meets the optical geometry, response time, and calibration traceability requirements of EEC Directive 72/306/EEC Annex II, including mandatory warm-up time ≤5 minutes and maximum permissible error limits (±10% FS). While not certified to ISO 11614 or EPA 40 CFR Part 1065 subpart J by default, its measurement principle and documented performance parameters align with the foundational metrological framework of those standards. For GLP/GMP-regulated environments, optional firmware upgrades support audit-trail logging of calibration events, operator ID tagging, and timestamped measurement records — compatible with FDA 21 CFR Part 11-compliant data management systems when paired with validated software clients.

Software & Data Management

The instrument supports bidirectional communication via ASCII-based RS-232 protocol, enabling remote configuration of measurement units, alarm thresholds, averaging intervals, and auto-zero frequency. Assemblad provides Windows-compatible PC software (OM00538EST001b/NET) for parameter setup, firmware updates, real-time waveform visualization, and export of time-stamped datasets in CSV or XML format. All calibration actions — including manual zeroing, reference span adjustment, and sensitivity verification — are logged with date/time stamps, user identifiers (if configured), and pre/post-calibration deviation metrics. Data files include embedded instrument serial number, firmware version, and environmental metadata (e.g., ambient temperature, battery voltage), facilitating full traceability in accredited laboratory audits.

Applications

• Periodic technical inspections (PTI) and roadside enforcement of diesel vehicle emissions compliance
• Engine development and calibration labs evaluating smoke-limited torque curves and EGR optimization strategies
• Chassis dynamometer testing where continuous opacity monitoring is required during WHTC or RMC cycles
• After-treatment system validation (DPF, DOC, SCR) through comparative smoke reduction quantification
• Training and certification programs for automotive technicians and emissions inspectors
• Research applications requiring high-temporal-resolution k-value time series for soot nucleation and agglomeration modeling

FAQ

What regulatory standards does the OPA-105.LCD comply with?
It conforms to EEC Directive 72/306/EEC for smoke emission testing of motor vehicles, specifically meeting requirements for optical path length (240 mm), thermal stabilization (≥70 °C), and maximum permissible error (±10% FS).
Can the OPA-105.LCD be used with dilution tunnels?
No — it is designed exclusively for raw exhaust sampling. Diluted streams require correction factors outside its certified operating envelope and invalidate compliance with EEC 72/306.
Is the internal battery user-replaceable?
Yes. The sealed 7.2 Ah 12 V rechargeable battery is field-serviceable using standard M5 fasteners; replacement part number is OM-BAT-7200-ASB.
Does the instrument support analog output (e.g., 4–20 mA)?
No — only digital RS-232 communication is provided. Analog conversion requires external interface hardware.
How often is recalibration recommended?
Annual calibration against NIST-traceable opacity standards is recommended for regulatory use; biannual verification is sufficient for internal quality control applications.