Operating Instructions - Snap-on Equipment

InterpretationDiscussionUnder certain conditions, the analyzer adds a dilution correction factor (DCF) tothe measured HC, CO, and NO values. This means the gas values reported in thetest results are greater than the gas values measured by the analyzer. The DCFwas developed by the State of California in 1994 to correct measured gas valuesfor exhaust system leaks.Select DCF OFF to see the measured gas values and select DCF ON to see thereported values. The DFC applied range is from 1.0 to 3.0. If the factor required is lessthan 1.0 or more than 3.0, the analyzer uses 1.0, which has no effect on gas values.Examples:measured gas x DCF = reported gas220 HC x 2.5 DCF = 550 PPM HC220 HC x 1.0 DCF = 220 PPM HC✓ Actual state I/M programs use:— DCF for Idle Test.— Both DCF and HCF for ASM Tests.Humidity Correction FactorsWhen using the Humidity Correction Factor (HCF) to report I/M results, select aHCF preference by choosing HCF ON or OFF.SpecificationsApplication:Purpose:Gas Value Affected:Affect:Factor Range: 0.739 – 2.52Temperature Range: 32 °F – 86 °FHumidity Range: 1% – 100%Barometric Pressure Range: 28.00" – 32.00" HgDiscussionCertain test resultsCorrects for water content of the ambient airNOHCF may increase or decrease gas valuesUnder certain conditions, the analyzer adjusts the measured NO (NO x ) value with ahumidity correction factor (HCF). This means that NO value reported with results maybe less or greater than NO values measured by the analyzer. Depending on currenttemperature, humidity, and barometric pressure conditions, the HCF may increase ordecrease the measured NO value. The EPA developed the HCF to compensate forrelative ambient humidity. The HCF is not applied during vehicle diagnosis.The HCF factor ranges from 0.739 to 2.52. The factor is applied over a widerange of temperatures (32 °F to 86 °F), humidities (1% to 100%), and pressures(28.00" to 32.00" Hg).Examples:measured NO x HCF = reported NO1500 ppm NO x 0.948 HCF = 1422 ppm NO1500 ppm NO x 2.03 HCF = 3045 ppm NOUsing Correction Factors (DCF and HCF) for RepairUse this simple, effective repair strategy to avoid any confusion based oncorrection factors.1. Pretest the vehicle with the analyzer program to obtain “baseline”emissions data.5-4