Overview
ISO 11614:1999 specifies requirements for apparatus (opacimeters) used to measure opacity and to determine the light absorption coefficient (k) of exhaust gas from reciprocating compression‑ignition (diesel) engines. The standard covers general principles, instrument design and installation, measurement conditions (steady and transient), data/instrumentation requirements, verification procedures and in‑service conformity checks. ISO 11614 replaces earlier ISO 3173:1974 and ISO/TR 4011:1976.
Key topics and technical requirements
- Principle of measurement: transmission of light through an exhaust gas path; opacity is the percentage of light prevented from reaching the receiver, and k is defined via the Beer–Lambert law. The standard notes temperature and pressure influence k and that readings must reference an optical path length.
- Opacimeter types: sampling (partial flow), in‑line full‑flow, end‑of‑line (plume‑type), and instruments for free‑acceleration tests - each with specific installation requirements.
- Performance specs:
- Indicator resolution: at least 0.1 % opacity.
- Zero and full‑scale stability: drift ≤ 0.5 % opacity or 2 % of full scale (whichever is smaller) over 1 hour or test duration.
- Effective optical path length must be defined and controlled (design and calibration considerations).
- Transient measurements: definitions and verification of response behavior including physical delay time, electrical and overall response times, temperature response time, and peak‑hold features.
- Verification & conformity: manufacturer data, type verification, performance checks, verification of response characteristics, and in‑service conformity procedures are specified.
- Data & instrumentation: requirements for sampling, signal conditioning, and test reporting; Annex A provides guidance for mean exhaust gas temperature in certain chambers.
Practical applications
- Ensuring reliable measurement of diesel exhaust opacity in engine test cells, R&D labs and certification facilities.
- Comparing emissions across engines or test conditions by providing standardized measurement and verification procedures.
- Selecting and installing opacimeters for engine bench tests, transient engine mapping, production testing, or regulatory compliance checks.
- Verifying instrument performance (type approval and periodic in‑service checks) to maintain measurement traceability and repeatability.
Who uses this standard
- Engine test laboratories and OEM R&D teams
- Emission test facilities and certification bodies
- Instrument manufacturers and calibration laboratories
- Regulatory agencies and environmental monitoring organizations
Related standards
Keywords: ISO 11614, opacimeter, opacity measurement, light absorption coefficient, exhaust gas, diesel engine emissions, transient response, instrument verification.