1. Time Alignment For Real Time Measurement

2. Time Alignment
Time Alignment is an important factor in the calculation of mass emissions from vehicles operating under transient conditions from raw exhaust measurements
Key parameters include :-
speed of response of the exhaust flow measurement
speed of response of the exhaust analysers
corrections for water content differences between exhaust flow rate and measured concentrations (exhaust flow is usually wet base, analysers can be wet or dry base)
Analyser interferences can be an issue
Ambient corrections to be considered (Nox correction, altitude)

3. HORIBA study on time alignment
EXSA-240 flow configuration
Response Time
EXSA-240 Nox/O2 analyser Speed of response

4. Nox is the main issue (EPA-505)

5. Other gases are not so sensitive - CO2

6. CO

7. HC - NDIR

8. OBS Time Alignment
OBS has freely adjustable time delays. Current setting is Td + T50
A check utility will be included to measure Td T50 and T90 in the future software for the OBS-2000 series

9. OBS Mass Calculations

10. Standard Mass Calculation
Mass Emissions Mass = Exhaust_Flow * Concentration * Density Where Exhaust flow = deg C / kPa Concentration = ppm/10e6 Density = standard densities (CFR) in deg C/101.3 kPa
Mass is calculated in 10 Hz basis and integrated
OBS-1000 does NOT correct the Nox mass for the Nox engine air humidity (Nox correction factor)