Document ID: chunk:federal_register_of_legislation:F2024L00447:reg:0:p18
Version: federal_register_of_legislation:F2024L00447
Segment Type: reg
Provision Reference: reg 0 (pt 18/57)
Character Range: 141061–144488

—   oxygen interference
F             —   water temperature [K]
G             —   saturation vapour pressure [kPa]
H             —   water vapour concentration [%]
Hm            —   maximum water vapour concentration [%]
NOX,dry       —   moisture-corrected mean concentration of the stabilized NOX recordings
NOX,m         —   mean concentration of the stabilized NOX recordings
NOX,ref       —   reference mean concentration of the stabilized NOX recordings
r2            —   coefficient of determination
t0            —   time point of gas flow switching [s]
t10           —        time point of 10 % response of the final reading
t50           —   time point of 50 % response of the final reading
t90           —   time point of 90 % response of the final reading
Tbd           —   to be determined
X             —   independent variable or reference value
xmin          —   minimum value
Y             —   dependent variable or measured value

3. Linearity verification
              3.1. General

              The accuracy and linearity of analysers, flow-measuring instruments, sensors and signals shall be traceable to international or national standards. Any sensors or signals that are not directly traceable (e.g., simplified flow-measuring instruments) shall be calibrated alternatively against chassis dynamometer laboratory equipment that has been calibrated against international or national standards.

              3.2. Linearity requirements

              All analysers, flow-measuring instruments, sensors and signals shall comply with the linearity requirements given in Table A5/1. If air flow, fuel flow, the air-to-fuel ratio or the exhaust mass flow rate is obtained from the ECU, the calculated exhaust mass flow rate shall meet the linearity requirements specified in Table A5/1.

    Table A5/1
    Linearity requirements of measurement parameters and systems

Measurement parameter/instrument                 Slope               Standard error of the estimate  Coefficient of determination r2
                                                 a1                  SEE
Fuel flow rate[14]                ≤ 1 % xmax      0.98 – 1.02         ≤ 2 %  of xmax                  ≥ 0.990

Air flow rate[15]                 ≤ 1 % xmax      0.98 – 1.02         ≤ 2 %  of xmax                  ≥ 0.990

Exhaust mass flow rate             ≤ 2 % xmax     0.97 – 1.03         ≤ 3 %  of xmax                  ≥ 0.990

Gas analysers                     ≤ 0.5 % max    0.99 – 1.01          ≤ 1 %  of xmax                  ≥ 0.998

Torque[16]                         ≤ 1 % xmax     0.98 – 1.02         ≤ 2 %  of xmax                  ≥ 0.990

PN analysers[17]                   ≤ 5 % xmax     0.85 – 1.15[18]     ≤ 10 %  of xmax                 ≥ 0.950

3.3. Frequency of linearity verification
              The linearity requirements pursuant to paragraph 3.2. shall be verified:

                  (a) For each gas analyser at least every 12 months or whenever a system repair or component change or modification is made that could influence the calibration;

                  (b) For other relevant instruments, such as PN 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