CFR > Title 40 - Protection of Environment > CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY > SUBCHAPTER C—AIR PROGRAMS (Parts 50–99) > PART 86—CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES > SUBPART D—Emission Regulations for New Gasoline-Fueled and Diesel-Fueled Heavy-Duty Engines; Gaseous Exhaust Test Procedures (§86.301-79 to §86.348-79) > 86.330-79—NDIR analyzer calibration.

86.330-79—NDIR analyzer calibration.

(a) Detector optimization. If necessary, follow the manufacturer's instructions for initial start-up and basic operating adjustments.
(b) Calibration curve. Develop a calibration curve for each range used as follows:
(1) Zero the analyzer.
(2) Span the analyzer to give a response of approximately 90 percent of full-scale chart deflection.
(3) Recheck the zero response. If it has changed more than 0.5 percent of full scale, repeat steps (1) and (2).
(4) Record the response of calibration gases having nominal concentrations of 15, 30, 45, 60, 75, and 90 percent of full-scale concentration.
(5) Generate a calibration curve. The calibration curve shall be of fourth order or less, have five or fewer coefficients, and be of the form of equation (1) or (2). Include zero as a data point. Compensation for known impurities in the zero gas can be made to the zero-data point. The calibration curve must fit the data points within 2 percent of point or 1 percent of full scale, whichever is less.
where:
y = concentration
x = chart deflection
(6) Option. A new calibration curve need not be generated if: (i) A calibration curve conforming to step (5) exists; (ii) The responses generated in step (4) are within 1 percent of full scale or 2 percent of point, whichever is less, of the responses predicted by the calibration curve for the gases used in step (4).
(7) If multiple range analyzers are used, only the lowest range must meet the curve fit requirements below 15 percent of full scale.
(c) If any range is within 2 percent of being linear a linear calibration may be used. To determine if this criterion is met:
(1) Perform a linear least-square regression on the data generated. Use an equation of the form y = mx, where x is the actual chart deflection and y is the concentration.
(2) Use the equation z = y/m to find the linear chart deflection (z) for each calibration gas concentration (y ).
(3) Determine the linearity (%L ) for each calibration gas by:
(4) The linearity criterion is met if the %L is less than ±2 percent for each data point generated. For each emission test, a calibration curve of the form Y = mx is to be used. The slope (m) is defined for each range by the spanning process.

Code of Federal Regulations

[42 FR 45154, Sept. 8, 1977, as amended at 46 FR 50495, Oct. 13, 1981; 47 FR 49807, Nov. 2, 1982]