MEXA-7200SLE

Analyzer Features

• Critical components are insulated to protect against temperature fluctuations - improves analyzer signal stability.
• CLD reaction chamber is smaller than previous LE model - boosts signal strength and minimizes noise.
• New vacuum pump in the CLD has a higher vacuum rate than previous LE model - increases measurement sensitivity and improves quench resolution.
• Volume of the GC sample loop is larger than previous LE model and column conditions have been optimized - increases measurement resolution.
• High voltage of the FID has been further stabilized - increases signal stability and minimizes noise.
• Analyzer electronics have been improved - increases sensitivity and minimizes noise.

MEXA-7200SLE includes these analyzers and ranges:

Signal-to-noise ratio is 2 times greater in the new FID and CLD and 1.5 times greater in the new GC-FID compared to the previous LE models.

O2 Interference Correction for THC Analyzer

MEXA-7200SLE includes an optional kit that allows the FIA-726SLE analyzer output to be corrected for O2 interference. This interference can occur when a bag mini-diluter (BMD) or CVS is used for sample dilution and bag collection. The effect - and benefit of compensation - is greatest when THC concentrations approach zero.

SF6 Mass Tracer Analyzer

To verify overall system accuracy during a test with vehicle exhaust, a known mass of inert gas is injected into the system and measured by the SF6 analyzer. Mass is calculated and compared to the known injected mass. This procedure is similar to a propane injection test but offers the advantage of running while a test is in progress.

SLE Sample Handling

MEXA-7200SLE's sample handling system incorporates the following features to assure measurement accuracy for SULEV emissions:

• Heated purge and backflush from the sample inlet to the THC analyzer minimizes HC contamination of the diluted exhaust sample from the CVS or BMD.
• Small manifold and simple flow schematic reduce the surface area exposed to sample gas, thus minimizing opportunities for HC adsorption and off-gassing.
• Stainless steel tube between the sample inlet and THC analyzer reduces HC adsorption and off-gassing.
• Idle purge function allows system to be continuously purged while not in use.
• New Teflon® tube provides approximately half the HC emissions of conventional Teflon® tubing.

A separate sample line is used to analyze CVS sample bag 1, since cold-start emissions are higher than subsequent test phases. A "clean" line is used for sample bags from subsequent test phases, all ambient bags, and all bags when a bag mini-diluter is used. Reduces the potential for HC contamination of clean samples.