On-Line System

octane determinations

Electronic Systems Design (ESD), formerly based in Palatine, Illinois, has been an industry leader for almost 50 years, focusing on innovative solutions for determining the octane ratings of fuels.


ESD is well-known for supplying On-Line and Laboratory Analyzers and for pioneering the use of the Falling Level Method (Dynamic Fuel Level) for octane number determination. Installation, parts and service are available throughout the world.


conforms to astm standards

ESD Representatives have been active participants in the development and maintenance of industry standards. All equipment meets or exceeds the requirements outlined in: ASTM D2699 Research Method, ASTM D2700 Motor Method and ASTM D2885 Test Method for Determining Octane Number of Spark-Ignition Fuels by On-Line Direct Comparison Technique.

Lab System

What is the falling level method?

The ESD Octane Analyzer Systems employ the well-known and proven Falling Level (Dynamic Fuel Level) Method for determining the octane number of a fuel sample. This method is documented in ASTM D2699 - Standard Method for Research Octane Number of Spark-Ignition Engine Fuel (Procedure B), ASTM D2700 - Standard Test Method for Motor Octane Number of Spark-Ignition Engine Fuel (Procedure B) and, by reference, in ASTM D2885 - Determination of Octane Number of Spark-Ignition Engine Fuels by On-Line Direct Comparison Technique.


With the Falling Level Method, a specifically designed and calibrated fuel supply bowl is filled and is allowed to empty as the CFR test engine runs. The bowl design is such that a test cycle on any fuel sample can be completed in a reasonable amount of time while ensuring that a consistent and repeatable range of fuel mixtures are delivered to the engine without the need for intervention by the operator.


As the liquid level in the supply bowl falls, the rate of fuel supplied to the engine decreases and the fuel / air ratio changes. The knock intensity of the engine is measured continuously over the range of fuel / air ratios. In a properly calibrated system, this is characterized by a light knock condition, through a peak knock measurement and then back to a light knock.


The peak knock intensity levels of fuels with known octane numbers higher and lower than the sample fuel are plotted in a straight-line graph. The sample's octane number can then be determined by the position of its measured peak knock intensity along this plotted curve. The Falling Level Method has been statistically proven and accepted by the ASTM as a valid octane number determination procedure.



By comparing peak knock intensity with known reference fuels, a simple straight-line interpolation reveals the octane number of the unknown fuel.



The Octamatic Octane Analyzer Systems are based on the Falling Level Method of measuring octane rating in fuel. This is a variant of the standard Bracketing Method (Procedure B) used by laboratories and refineries.


Determination of the proper fuel / air ratio is far more accurate than that obtained by manual methods. Unlike manual methods, the operator is out of the control loop which determines peak fuel / air ratio. Errors in recording, transcribing and calculating octane numbers are eliminated.


There are two versions of the ESD Octamatic Analyzer: The ON-LINE SYSTEM and the LABORATORY SYSTEM. Both systems use the same high precision methods as described in ASTM D2699, ASTM D2700 and ASTM D2885.

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  • Economical with a fast payback on investment. Can run tests on multiple engines simultaneously and the system precision reduces octane "giveaway".
  • In compliance with ASTM Standards: D2699 Research Method, D2700 Motor Method and D2885 Test Method for Determining Octane Number of Spark-Ignition Fuels by On-Line Direct Comparison Techniques.
  • Very precise system eliminating manual data calculation and recording. Frees operator from continually adjusting fuel / air ratio.
  • Always finds the fuel / air mixture resulting in maximum engine knock. Fuel / air ratio is adjusted automatically by the falling level of the fuel bowl.