Document ID: chunk:federal_register_of_legislation:F2024L00447:reg:0:p19
Version: federal_register_of_legislation:F2024L00447
Segment Type: reg
Provision Reference: reg 0 (pt 19/57)
Character Range: 144199–147348

analysers, exhaust mass flow meters and traceably calibrated sensors, whenever damage is observed, as required by internal audit procedures or by the instrument manufacturer but no longer than one year before the actual test.

              The linearity requirements pursuant to paragraph 3.2. for sensors or ECU signals that are not directly traceable shall be performed using a measurement device with a traceable calibration on the chassis dynamometer, once for each PEMS-vehicle setup.

              3.4. Procedure of linearity verification

              3.4.1. General requirements

              The relevant analysers, instruments and sensors shall be brought to their normal operating condition according to the recommendations of their manufacturer. The analysers, instruments and sensors shall be operated at their specified temperatures, pressures and flows.

              3.4.2. General procedure

              The linearity shall be verified for each normal operating range by executing the following steps:

                  (a) The analyser, flow-measuring instrument or sensor shall be set to zero by introducing a zero signal. For gas analysers, purified synthetic air or nitrogen shall be introduced to the analyser port via a gas path that is as direct and short as possible.

                  (b) The analyser, flow-measuring instrument or sensor shall be spanned by introducing a span signal. For gas analysers, an appropriate span gas shall be introduced to the analyser port via a gas path that is as direct and short as possible.

                  (c) The zero procedure of (a) shall be repeated.

                  (d) The linearity shall be verified by introducing at least 10, approximately equally spaced and valid, reference values (including zero). The reference values with respect to the concentration of components, the exhaust mass flow rate or any other relevant parameter shall be chosen to match the range of values expected during the emissions test. For measurements of exhaust mass flow, reference points below 5 per cent of the maximum calibration value can be excluded from the linearity verification.

                  (e) For gas analysers, known gas concentrations in accordance with paragraph 5. shall be introduced to the analyser port. Sufficient time for signal stabilisation shall be given. For particle number analysers, the particle number concentrations shall be at least two times the limit of detection (defined in paragraph 6.2.).

                  (f) The values under evaluation and, if needed, the reference values shall be recorded at a constant frequency which is a multiple of 1.0 Hz over a period of 30 seconds (60 s for particle number analysers).

                  (g) The arithmetic mean values over the 30 seconds (or 60 s) period shall be used to calculate the least squares linear regression parameters, with the best-fit equation having the form:

                  where:

              y is the actual value of the measurement system

              a1 is the slope of the regression line

              x is the reference value

              a0 is the y intercept