§ 169.8. Instrument checks.
(a) Smoke opacimeter. The smoke opacimeter shall be checked according to the following procedure prior to each test:
(1) Check the surfaces of the optical section to verify that they are clean and free from foreign material and fingerprints.
(2) Adjust the zero control under conditions of ‘‘no smoke’’ to give a recorder trace of zero.
(3) Use calibrated neutral density filters having approximately 10%, 20% and 40% opacity to check the linearity of the instrument. Deviations in excess of 1% of the calibrated value of a filter should be corrected.
(i) Insert the filter in the light path perpendicular to the axis of the beam and adjacent to the opening from which the beam of light from the light source emanates and note the recorder response.
(ii) For maximum correlation of results, the calibration of the neutral density filters should be traceable to the United States National Bureau of Standards.
(b) Other instruments. The instruments for measuring engine speed, torque, air inlet restrictions, exhaust system back pressure, fuel rate and so forth, and for recording engine speed and smoke opacity used in the tests prescribed herein shall be calibrated periodically in accordance with good technical practice.
Source The provisions of this § 169.8 adopted August 26, 1977, effective August 27, 1977, 7 Pa.B. 2432.
Cross References This section cited in 67 Pa. Code § 169.4 (relating to smoke emission test).
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