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(c) Recirculating fuel. In any fuel-flow measurement, account for any fuel that bypasses the engine or returns from the engine to the fuel storage tank.
(d) Flow conditioning. For any type of fuel flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. You may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, straightening fins, or pneumatic pulsation dampeners to establish a steady and predictable velocity profile upstream of the meter.
§ 1065.225 Intake-air flow meter.
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(a) Application. You may use an intake-air flow meter in combination with a chemical balance of carbon (or oxygen) between the fuel, inlet air, and raw exhaust to calculate raw exhaust flow as described in §1065.650, as follows:
(1) Use the actual value of calculated raw exhaust in the following cases:
(i) For multiplying raw exhaust flow rate with continuously sampled concentrations.
(ii) For multiplying total raw exhaust flow with batch-sampled concentrations.
(2) In the following cases, you may use an intake-air flow meter signal that does not give the actual value of raw exhaust, as long as it is linearly proportional to the exhaust flow rate's actual calculated value:
(i) For feedback control of a proportional sampling system, such as a partial-flow dilution system.
(ii) For multiplying with continuously sampled gas concentrations, if the same signal is used in a chemical-balance calculation to determine work from brake-specific fuel consumption and fuel consumed.
(b) Component requirements. We recommend that you use an intake-air flow meter that meets the specifications in Table 1 of §1065.205. This may include a laminar flow element, an ultrasonic flow meter, a subsonic venturi, a thermal-mass meter, an averaging Pitot tube, or a hot-wire anemometer. Note that your overall system for measuring intake-air flow must meet the linearity verification in §1065.307 and the calibration in §1065.325.
(c) Flow conditioning. For any type of intake-air flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. You may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of the meter.
§ 1065.230 Raw exhaust flow meter.
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(a) Application. You may use measured raw exhaust flow, as follows:
(1) Use the actual value of calculated raw exhaust in the following cases:
(i) Multiply raw exhaust flow rate with continuously sampled concentrations.
(ii) Multiply total raw exhaust with batch sampled concentrations.
(2) In the following cases, you may use a raw exhaust flow meter signal that does not give the actual value of raw exhaust, as long as it is linearly proportional to the exhaust flow rate's actual calculated value:
(i) For feedback control of a proportional sampling system, such as a partial-flow dilution system.
(ii) For multiplying with continuously sampled gas concentrations, if the same signal is used in a chemical-balance calculation to determine work from brake-specific fuel consumption and fuel consumed.
(b) Component requirements. We recommend that you use a raw-exhaust flow meter that meets the specifications in Table 1 of §1065.205. This may involve using an ultrasonic flow meter, a subsonic venturi, an averaging Pitot tube, a hot-wire anemometer, or other measurement principle. This would generally not involve a laminar flow element or a thermal-mass meter. Note that your overall system for measuring raw exhaust flow must meet the linearity verification in §1065.307 and the calibration and verifications in §1065.330. Any raw-exhaust meter must be designed to appropriately compensate for changes in the raw exhaust's thermodynamic, fluid, and compositional states.
(c) Flow conditioning. For any type of raw exhaust flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. You may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of the meter.
(d) Exhaust cooling. You may cool raw exhaust upstream of a raw-exhaust flow meter, as long as you observe all the following provisions:
(1) Do not sample PM downstream of the cooling.
(2) If cooling causes exhaust temperatures above 202 °C to decrease to below 180 °C, do not sample NMHC downstream of the cooling for compression-ignition engines, 2-stroke spark-ignition engines, and 4-stroke spark-ignition engines below 19 kW.
(3) If cooling causes aqueous condensation, do not sample NOX downstream of the cooling unless the cooler meets the performance verification in §1065.376.
(4) If cooling causes aqueous condensation before the flow reaches a flow meter, measure dewpoint, Tdew and pressure, ptotal at the flow meter inlet. Use these values in emission calculations according to §1065.650.
§ 1065.240 Dilution air and diluted exhaust flow meters.
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(a) Application. Use a diluted exhaust flow meter to determine instantaneous diluted exhaust flow rates or total diluted exhaust flow over a test interval. You may use the difference between a diluted exhaust flow meter and a dilution air meter to calculate raw exhaust flow rates or total raw exhaust flow over a test interval.
(b) Component requirements. We recommend that you use a diluted exhaust flow meter that meets the specifications in Table 1 of §1065.205. Note that your overall system for measuring diluted exhaust flow must meet the linearity verification in §1065.307 and the calibration and verifications in §1065.340 and §1065.341. You may use the following meters:
(1) For constant-volume sampling (CVS) of the total flow of diluted exhaust, you may use a critical-flow venturi (CFV) or multiple critical-flow venturis arranged in parallel, a positive-displacement pump (PDP), a subsonic venturi (SSV), or an ultrasonic flow meter (UFM). Combined with an upstream heat exchanger, either a CFV or a PDP will also function as a passive flow controller in a CVS system. However, you may also combine any flow meter with any active flow control system to maintain proportional sampling of exhaust constituents. You may control the total flow of diluted exhaust, or one or more sample flows, or a combination of these flow controls to maintain proportional sampling.
(2) For any other dilution system, you may use a laminar flow element, an ultrasonic flow meter, a subsonic venturi, a critical-flow venturi or multiple critical-flow venturis arranged in parallel, a positive-displacement meter, a thermal-mass meter, an averaging Pitot tube, or a hot-wire anemometer.
(c) Flow conditioning. For any type of diluted exhaust flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. For some meters, you may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of the meter.
(d) Exhaust cooling. You may cool diluted exhaust upstream of a raw-exhaust flow meter, as long as you observe all the following provisions:
(1) Do not sample PM downstream of the cooling.
(2) If cooling causes exhaust temperatures above 202 °C to decrease to below 180 °C, do not sample NMHC downstream of the cooling for compression-ignition engines, 2-stroke spark-ignition engines, and 4-stroke spark-ignition engines below 19 kW.
(3) If cooling causes aqueous condensation, do not sample NOX downstream of the cooling unless the cooler meets the performance verification in §1065.376.
(4) If cooling causes aqueous condensation before the flow reaches a flow meter, measure dewpoint, Tdew and pressure, ptotal at the flow meter inlet. Use these values in emission calculations according to §1065.650.
§ 1065.245 Sample flow meter for batch sampling.
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(a) Application. Use a sample flow meter to determine sample flow rates or total flow sampled into a batch sampling system over a test interval. You may use the difference between a diluted exhaust sample flow meter and a dilution air meter to calculate raw exhaust flow rates or total raw exhaust flow over a test interval.
(b) Component requirements. We recommend that you use a sample flow meter that meets the specifications in Table 1 of §1065.205. This may involve a laminar flow element, an ultrasonic flow meter, a subsonic venturi, a critical-flow venturi or multiple critical-flow venturis arranged in parallel, a positive-displacement meter, a thermal-mass meter, an averaging Pitot tube, or a hot-wire anemometer. Note that your overall system for measuring sample flow must meet the linearity verification in §1065.307. For the special case where CFVs are used for both the diluted exhaust and sample-flow measurements and their upstream pressures and temperatures remain similar during testing, you do not have to quantify the flow rate of the sample-flow CFV. In this special case, the sample-flow CFV inherently flow-weights the batch sample relative to the diluted exhaust CFV.
(c) Flow conditioning. For any type of sample flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. For some meters, you may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of the meter.
§ 1065.248 Gas divider.
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(a) Application. You may use a gas divider to blend calibration gases.
(b) Component requirements. Use a gas divider that blends gases to the specifications of §1065.750 and to the flow-weighted concentrations expected during testing. You may use critical-flow gas dividers, capillary-tube gas dividers, or thermal-mass-meter gas dividers. Note that your overall gas-divider system must meet the linearity verification in §1065.307.
CO and CO2 Measurements
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§ 1065.250 Nondispersive infra-red analyzer.
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(a) Application. Use a nondispersive infra-red (NDIR) analyzer to measure CO and CO2 concentrations in raw or diluted exhaust for either batch or continuous sampling.
(b) Component requirements. We recommend that you use an NDIR analyzer that meets the specifications in Table 1 of §1065.205. Note that your NDIR-based system must meet the calibration and verifications in §1065.350 and §1065.355 and it must also meet the linearity verification in §1065.307. You may use an NDIR analyzer that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.
Hydrocarbon Measurements
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§ 1065.260 Flame-ionization detector.
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(a) Application. Use a flame-ionization detector (FID) analyzer to measure hydrocarbon concentrations in raw or diluted exhaust for either batch or continuous sampling. Determine hydrocarbon concentrations on a carbon number basis of one, C1. Determine methane and nonmethane hydrocarbon values as described in paragraph (e) of this section. See subpart I of this part for special provisions that apply to measuring hydrocarbons when testing with oxygenated fuels.
(b) Component requirements. We recommend that you use a FID analyzer that meets the specifications in Table 1 of §1065.205. Note that your FID-based system for measuring THC, THCE, or CH4 must meet all of the verifications for hydrocarbon measurement in subpart D of this part, and it must also meet the linearity verification in §1065.307. You may use a FID that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.
(c) Heated FID analyzers. For diesel-fueled engines, two-stroke spark-ignition engines, and four-stroke spark-ignition engines below 19 kW, you must use heated FID analyzers that maintain all surfaces that are exposed to emissions at a temperature of (191 ±11) °C.
(d) FID fuel and burner air. Use FID fuel and burner air that meet the specifications of §1065.750. Do not allow the FID fuel and burner air to mix before entering the FID analyzer to ensure that the FID analyzer operates with a diffusion flame and not a premixed flame.
(e) Methane. FID analyzers measure total hydrocarbons (THC). To determine nonmethane hydrocarbons (NMHC), quantify methane, CH4, either with a nonmethane cutter and a FID analyzer as described in §1065.265, or with a gas chromatograph as described in §1065.267. Instead of measuring methane, you may assume that 2% of measured total hydrocarbons is methane, as described in §1065.660. For a FID analyzer used to determine NMHC, determine its response factor to CH4, RFCH4, as described in §1065.360. Note that NMHC-related calculations are described in §1065.660.
§ 1065.265 Nonmethane cutter.
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(a) Application. You may use a nonmethane cutter to measure CH4 with a FID analyzer. A nonmethane cutter oxidizes all nonmethane hydrocarbons to CO2 and H2O. You may use a nonmethane cutter for raw or diluted exhaust for batch or continuous sampling.
(b) System performance. Determine nonmethane-cutter performance as described in §1065.365 and use the results to calculate NMHC emission in §1065.660.
(c) Configuration. Configure the nonmethane cutter with a bypass line for the verification described in §1065.365.
(d) Optimization. You may optimize a nonmethane cutter to maximize the penetration of CH4 and the oxidation of all other hydrocarbons. You may humidify a sample and you may dilute a sample with purified air or oxygen (O2) upstream of the nonmethane cutter to optimize its performance. You must account for any sample humidification and dilution in emission calculations.
§ 1065.267 Gas chromatograph.
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(a) Application. You may use a gas chromatograph to measure CH4 concentrations of diluted exhaust for batch sampling. While you may also use a nonmethane cutter to measure CH4, as described in §1065.265, use a reference procedure based on a gas chromatograph for comparison with any proposed alternate measurement procedure under §1065.10.
(b) Component requirements. We recommend that you use a gas chromatograph that meets the specifications in Table 1 of §1065.205, and it must also meet the linearity verification in §1065.307.
NOX Measurements
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§ 1065.270 Chemiluminescent detector.
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(a) Application. You may use a chemiluminescent detector (CLD) to measure NOX concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept a CLD for NOX measurement, even though it measures only NO and NO2, when coupled with an NO2-to-NO converter, since conventional engines and aftertreatment systems do not emit significant amounts of NOX species other than NO and NO2. Measure other NOX species if required by the standard-setting part. While you may also use other instruments to measure NOX, as described in §1065.272, use a reference procedure based on a chemiluminescent detector for comparison with any proposed alternate measurement procedure under §1065.10.
(b) Component requirements. We recommend that you use a CLD that meets the specifications in Table 1 of §1065.205. Note that your CLD-based system must meet the quench verification in §1065.370 and it must also meet the linearity verification in §1065.307. You may use a heated or unheated CLD, and you may use a CLD that operates at atmospheric pressure or under a vacuum. You may use a CLD that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.
(c) NO2-to-NO converter. Place upstream of the CLD an internal or external NO2-to-NO converter that meets the verification in §1065.378. Configure the converter with a bypass to facilitate this verification.
(d) Humidity effects. You must maintain all CLD temperatures to prevent aqueous condensation. To remove humidity from a sample upstream of a CLD, use one of the following configurations:
(1) Connect a CLD downstream of any dryer or chiller that is downstream of an NO2-to-NO converter that meets the verification in §1065.378.
(2) Connect a CLD downstream of any dryer or thermal chiller that meets the verification in §1065.376.
(e) Response time. You may use a heated CLD to improve CLD response time.
§ 1065.272 Nondispersive ultraviolet analyzer.
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(a) Application. You may use a nondispersive ultraviolet (NDUV) analyzer to measure NOX concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept an NDUV for NOX measurement, even though it measures only NO and NO2, since conventional engines and aftertreatment systems do not emit significant amounts of other NOX species. Measure other NOX species if required by the standard-setting part.
(b) Component requirements. We recommend that you use an NDUV analyzer that meets the specifications in Table 1 of §1065.205. Note that your NDUV-based system must meet the verifications in §1065.372 and it must also meet the linearity verification in §1065.307. You may use a NDUV analyzer that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.
(c) NO2-to-NO converter. If your NDUV analyzer measures only NO, place upstream of the NDUV analyzer an internal or external NO2-to-NO converter that meets the verification in §1065.378. Configure the converter with a bypass to facilitate this verification.
(d) Humidity effects. You must maintain NDUV temperature to prevent aqueous condensation, unless you use one of the following configurations:
(1) Connect an NDUV downstream of any dryer or chiller that is downstream of an NO2-to-NO converter that meets the verification in §1065.378.
(2) Connect an NDUV downstream of any dryer or thermal chiller that meets the verification in §1065.376.
O2 Measurements
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§ 1065.280 Paramagnetic and magnetopneumatic O2 detection analyzers.
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(a) Application. You may use a paramagnetic detection (PMD) or magnetopneumatic detection MPD) analyzer to measure O2 concentration in raw or diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow measurements to calculate exhaust flow rate according to §1065.650.
(b) Component requirements. We recommend that you use a PMD/MPD analyzer that meets the specifications in Table 1 of §1065.205. Note that it must meet the linearity verification in §1065.307. You may use a PMD/MPD that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.
Air-to-Fuel Ratio Measurements
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§ 1065.284 Zirconia (ZrO2) analyzer.
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(a) Application. You may use a zirconia (ZrO2) analyzer to measure air-to-fuel ratio in raw exhaust for continuous sampling. You may use O2 measurements with intake air or fuel flow measurements to calculate exhaust flow rate according to §1065.650.
(b) Component requirements. We recommend that you use a ZrO2 analyzer that meets the specifications in Table 1 of §1065.205. Note that your ZrO2-based system must meet the linearity verification in §1065.307. You may use a Zirconia analyzer that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.
PM Measurements
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§ 1065.290 PM gravimetric balance.
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(a) Application. Use a balance to weigh net PM on a sample medium for laboratory testing.
(b) Component requirements. We recommend that you use a balance that meets the specifications in Table 1 of §1065.205. Note that your balance-based system must meet the linearity verification in §1065.307. If the balance uses internal calibration weights for routine spanning and linearity verifications, the calibration weights must meet the specifications in §1065.790. While you may also use an inertial balance to measure PM, as described in §1065.295, use a reference procedure based on a gravimetric balance for comparison with any proposed alternate measurement procedure under §1065.10.
(c) Pan design. We recommend that you use a balance pan designed to minimize corner loading of the balance, as follows:
(1) Use a pan that centers the PM sample on the weighing pan. For example, use a pan in the shape of a cross that has upswept tips that center the PM sample media on the pan.
(2) Use a pan that positions the PM sample as low as possible.
(d) Balance configuration. Configure the balance for optimum settling time and stability at your location.
§ 1065.295 PM inertial balance for field-testing analysis.
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(a) Application. You may use an inertial balance to quantify net PM on a sample medium for field testing.
(b) Component requirements. We recommend that you use a balance that meets the specifications in Table 1 of §1065.205. Note that your balance-based system must meet the linearity verification in §1065.307. If the balance uses an internal calibration process for routine spanning and linearity verifications, the process must be NIST-traceable. You may use an inertial PM balance that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.
Subpart D—Calibrations and Verifications
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§ 1065.301 Overview and general provisions.
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(a) This subpart describes required and recommended calibrations and verifications of measurement systems. See subpart C of this part for specifications that apply to individual instruments.
(b) You must generally use complete measurement systems when performing calibrations or verifications in this subpart. For example, this would generally involve evaluating instruments based on values recorded with the complete system you use for recording test data, including analog-to-digital converters. For some calibrations and verifications, we may specify that you disconnect part of the measurement system to introduce a simulated signal.
(c) If we do not specify a calibration or verification for a portion of a measurement system, calibrate that portion of your system and verify its performance at a frequency consistent with any recommendations from the measurement-system manufacturer, consistent with good engineering judgment.
(d) Use NIST-traceable standards to the tolerances we specify for calibrations and verifications. Where we specify the need to use NIST-traceable standards, you may alternatively ask for our approval to use international standards that are not NIST-traceable.
§ 1065.303 Summary of required calibration and verifications.
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The following table summarizes the required and recommended calibrations and verifications described in this subpart and indicates when these have to be performed:
Table 1 of § 1065.303_Summary of Required Calibration and
Verifications
------------------------------------------------------------------------
Type of calibration or
verification Minimum frequency \a\
------------------------------------------------------------------------
§ 1065.305: accuracy, Accuracy: Not required, but recommended
repeatability and noise. for initial installation.
Repeatability: Not required, but
recommended for initial installation.
Noise: Not required, but recommended for
initial installation.
§ 1065.307: linearity... Speed: Upon initial installation, within
370 days before testing and after major
maintenance.
Torque: Upon initial installation, within
370 days before testing and after major
maintenance.
Electrical power: Upon initial
installation, within 370 days before
testing and after major maintenance.
Clean gas and diluted exhaust flows: Upon
initial installation, within 370 days
before testing and after major
maintenance, unless flow is verified by
propane check or by carbon or oxygen
balance.
Raw exhaust flow: Upon initial
installation, within 185 days before
testing and after major maintenance,
unless flow is verified by propane check
or by carbon or oxygen balance.
Gas analyzers: Upon initial installation,
within 35 days before testing and after
major maintenance.
PM balance: Upon initial installation,
within 370 days before testing and after
major maintenance.
Stand-alone pressure and temperature:
Upon initial installation, within 370
days before testing and after major
maintenance.
§ 1065.308: Continuous Upon initial installation, after system
analyzer system response and reconfiguration, and after major
recording. maintenance.
§ 1065.309: Continuous Upon initial installation, after system
analyzer uniform response. reconfiguration, and after major
maintenance.
§ 1065.310: torque...... Upon initial installation and after major
maintenance.
§ 1065.315: pressure, Upon initial installation and after major
temperature, dewpoint. maintenance.
§ 1065.320: fuel flow... Upon initial installation and after major
maintenance.
§ 1065.325: intake flow. Upon initial installation and after major
maintenance.
§ 1065.330: exhaust flow Upon initial installation and after major
maintenance.
§ 1065.340: diluted Upon initial installation and after major
exhaust flow (CVS). maintenance.
§ 1065.341: CVS and Upon initial installation, within 35 days
batch sampler verification. before testing, and after major
maintenance.
§ 1065.345: vacuum leak. Before each laboratory test according to
subpart F of this part and before each
field test according to subpart J of
this part.
§ 1065.350: CO2 NDIR H2O Upon initial installation and after major
interference. maintenance.
§ 1065.355: CO NDIR CO2 Upon initial installation and after major
and H2O interference. maintenance.
§ 1065.360: FID Calibrate, optimize, and determine CH4
optimization, etc.. response: upon initial installation and
after major maintenance.
Verify CH4 response: upon initial
installation, within 185 days before
testing, and after major maintenance.
§ 1065.362: raw exhaust Upon initial installation, after FID
FID O2 interference. optimization according to §
1065.360, and after major maintenance.
§ 1065.365: nonmethane Upon initial installation, within 185
cutter penetration. days before testing, and after major
maintenance.
§ 1065.370: CLD CO2 and Upon initial installation and after major
H2O quench. maintenance.
§ 1065.372: NDUV HC and Upon initial installation and after major
H2O interference. maintenance.
§ 1065.376: chiller NO2 Upon initial installation and after major
penetration. maintenance.
§ 1065.378: NO2-to-NO Upon initial installation, within 35 days
converter conversion. before testing, and after major
maintenance.
§ 1065.390: PM balance Independent verification: upon initial
and weighing. installation, within 370 days before
testing, and after major maintenance.
Zero, span, and reference sample
verifications: within 12 hours of
weighing, and after major maintenance.
§ 1065.395: Inertial PM Independent verification: upon initial
balance and weighing. installation, within 370 days before
testing, and after major maintenance.
Other verifications: upon initial
installation and after major
maintenance.
------------------------------------------------------------------------
\a\ Perform calibrations and verifications more frequently, according to
measurement system manufacturer instructions and good engineering
judgment.
§ 1065.305 Verifications for accuracy, repeatability, and noise.
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(a) This section describes how to determine the accuracy, repeatability, and noise of an instrument. Table 1 of §1065.205 specifies recommended values for individual instruments.
(b) We do not require you to verify instrument accuracy, repeatability, or noise.
However, it may be useful to consider these verifications to define a specification for a new instrument, to verify the performance of a new instrument upon delivery, or to troubleshoot an existing instrument.
(c) In this section we use the letter “y” to denote a generic measured quantity, the superscript over-bar to denote an arithmetic mean (such as y ), and the subscript “ref” to denote the reference quantity being measured.
(d) Conduct these verifications as follows:
(1) Prepare an instrument so it operates at its specified temperatures, pressures, and flows. Perform any instrument linearization or calibration procedures prescribed by the instrument manufacturer.
(2) Zero the instrument as you would before an emission test by introducing a zero signal. Depending on the instrument, this may be a zero-concentration gas, a reference signal, a set of reference thermodynamic conditions, or some combination of these. For gas analyzers, use a zero gas that meets the specifications of §1065.750.
(3) Span the instrument as you would before an emission test by introducing a span signal. Depending on the instrument, this may be a span-concentration gas, a reference signal, a set of reference thermodynamic conditions, or some combination of these. For gas analyzers, use a span gas that meets the specifications of §1065.750.
(4) Use the instrument to quantify a NIST-traceable reference quantity, yref. For gas analyzers the reference gas must meet the specifications of §1065.750. Select a reference quantity near the mean value expected during testing. For all gas analyzers, use a quantity near the flow-weighted mean concentration expected at the standard or expected during testing, whichever is greater. For a noise verfication, use the same zero gas from paragraph (e) of this section as the reference quantity. In all cases, allow time for the instrument to stabilize while it measures the reference quantity. Stabilization time may include time to purge an instrument and time to account for its response.
(5) Sample and record values for 30 seconds, record the arithmetic mean, y i, and record the standard deviation, si, of the recorded values. Refer to §1065.602 for an example of calculating arithmetic mean and standard deviation.
(6) Also, if the reference quantity is not absolutely constant, which might be the case with a reference flow, sample and record values of yrefi for 30 seconds and record the arithmetic mean of the values, y ref. Refer to §1065.602 for an example of calculating arithmetic mean.
(7) Subtract the reference value, yref (or y ref), from the arithmetic mean, y i. Record this value as the error, ei.
(8) Repeat the steps specified in paragraphs (d)(2) through (6) of this section until you have ten arithmetic means (y 1, y 2, y i,. . . y 10), ten standard deviations, (s1, s2, si,. . .s10), and ten errors (e1, e2, ei,. . .e10).
(9) Use the following values to quantify your measurements:
(i) Accuracy. Instrument accuracy is the absolute difference between the reference quantity, yref (or y ref), and the arithmetic mean of the ten y i, y values. Refer to the example of an accuracy calculation in §1065.602. We recommend that instrument accuracy be within the specifications in Table 1 of §1065.205.
(ii) Repeatability. Repeatability is two times the standard deviation of the ten errors (that is, repeatability = 2 · se). Refer to the example of a standard-deviation calculation in §1065.602. We recommend that instrument repeatability be within the specifications in Table 1 of §1065.205.
(iii) Noise. Noise is two times the root-mean-square of the ten standard deviations (that is, noise = 2 · rmss) when the reference signal is a zero-quantity signal. Refer to the example of a root-mean-square calculation in §1065.602. We recommend that instrument noise be within the specifications in Table 1 of §1065.205. Use this value in the noise correction specified in §1065.657.
(10) You may use a measurement instrument that does not meet the accuracy, repeatability, or noise specifications in Table 1 of §1065.205, as long as you meet the following criteria:
(i) Your measurement systems meet all the other required calibration, verification, and validation specifications in subparts D, F, and J of this part, as applicable.
(ii) The measurement deficiency does not adversely affect your ability to demonstrate compliance with the applicable standards.
§ 1065.307 Linearity verification.
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(a) Scope and frequency. Perform a linearity verification on each measurement system listed in Table 1 of this section at least as frequently as indicated in the table, consistent with measurement system manufacturer recommendations and good engineering judgment. Note that this linearity verification may replace requirements we previously referred to as “calibrations”. The intent of a linearity verification is to determine that a measurement system responds proportionally over the measurement range of interest. A linearity verification generally consists of introducing a series of at least 10 reference values to a measurement system. The measurement system quantifies each reference value. The measured values are then collectively compared to the reference values by using a least squares linear regression and the linearity criteria specified in Table 1 of this section.
(b) Performance requirements. If a measurement system does not meet the applicable linearity criteria in Table 1 of this section, correct the deficiency by re-calibrating, servicing, or replacing components as needed. Before you may use a measurement system that does not meet linearity criteria, you must demonstrate to us that the deficiency does not adversely affect your ability to demonstrate compliance with the applicable standards.
(c) Procedure. Use the following linearity verification protocol, or use good engineering judgment to develop a different protocol that satisfies the intent of this section, as described in paragraph (a) of this section:
(1) In this paragraph (c), we use the letter “y” to denote a generic measured quantity, the superscript over-bar to denote an arithmetic mean (such as y ), and the subscript “ref” to denote the known or reference quantity being measured.
(2) Operate a measurement system at its specified temperatures, pressures, and flows. This may include any specified adjustment or periodic calibration of the measurement system.
(3) Zero the instrument as you would before an emission test by introducing a zero signal. Depending on the instrument, this may be a zero-concentration gas, a reference signal, a set of reference thermodynamic conditions, or some combination of these. For gas analyzers, use a zero gas that meets the specifications of §1065.750 and introduce it directly at the analyzer port.
(4) Span the instrument as you would before an emission test by introducing a span signal. Depending on the instrument, this may be a span-concentration gas, a reference signal, a set of reference thermodynamic conditions, or some combination of these. For gas analyzers, use a span gas that meets the specifications of §1065.750 and introduce it directly at the analyzer port.
(5) After spanning the instrument, check zero with the same signal you used in paragraph (c)(3) of this section. Based on the zero reading, use good engineering judgment to determine whether or not to rezero and or re-span the instrument before proceeding to the next step.
(6) Use instrument manufacturer recommendations and good engineering judgment to select at least 10 reference values, yrefi, that are within the range from zero to the highest values expected during emission testing. We recommend selecting a zero reference signal as one of the reference values of the linearity verification.
(7) Use instrument manufacturer recommendations and good engineering judgment to select the order in which you will introduce the series of reference values. For example you may select the reference values randomly to avoid correlation with previous measurements, you may select reference values in ascending or descending order to avoid long settling times of reference signals, or as another example you may select values to ascend and then descend which might incorporate the effects of any instrument hysteresis into the linearity verification.
(8) Generate reference quantities as described in paragraph (d) of this section. For gas analyzers, use gas concentrations known to be within the specifications of §1065.750 and introduce them directly at the analyzer port.
(9) Introduce a reference signal to the measurement instrument.
(10) Allow time for the instrument to stabilize while it measures the reference value. Stabilization time may include time to purge an instrument and time to account for its response.
(11) At a recording frequency of at least f Hz, specified in Table 1 of §1065.205, measure the reference value for 30 seconds and record the arithmetic mean of the recorded values, y i. Refer to §1065.602 for an example of calculating an arithmetic mean.
(12) Repeat steps in paragraphs (c)(9) through (11) of this section until all reference quantities are measured.
(13) Use the arithmetic means y i, and reference values, yrefi , to calculate least-squares linear regression parameters and statistical values to compare to the minimum performance criteria specified in Table 1 of this section. Use the calculations described in §1065.602.
(d) Reference signals. This paragraph (d) describes recommended methods for generating reference values for the linearity-verification protocol in paragraph (c) of this section. Use reference values that simulate actual values, or introduce an actual value and measure it with a reference-measurement system. In the latter case, the reference value is the value reported by the reference-measurement system. Reference values and reference-measurement systems must be NIST-traceable. We recommend using calibration reference quantities that are NIST-traceable within 0.5% uncertainty, if not specified otherwise in other sections of this part 1065. Use the following recommended methods to generate reference values or use good engineering judgment to select a different reference:
(1) Engine speed. Run the engine or dynamometer at a series of steady-state speeds and use a strobe, a photo tachometer, or a laser tachometer to record reference speeds.
(2) Engine torque. Use a series of calibration weights and a calibration lever arm to simulate engine torque. You may instead use the engine or dynamometer itself to generate a nominal torque that is measured by a reference load cell or proving ring in series with the torque-measurement system. In this case use the reference load cell measurement as the reference value. Refer to §1065.310 for a torque-calibration procedure similar to the linearity verification in this section.
(3) Electrical work. Use a controlled source of current and a watt-hour standard reference meter. Complete calibration systems that contain a current source and a reference watt-hour meter are commonly used in the electrical power distribution industry and are therefore commercially available.
(4) Fuel rate. Operate the engine at a series of constant fuel-flow rates or re-circulate fuel back to a tank through the fuel flow meter at different flow rates. Use a gravimetric reference measurement (such as a scale, balance, or mass comparator) at the inlet to the fuel-measurement system. Use a stopwatch or timer to measure the time intervals over which reference masses of fuel are introduced to the fuel measurement system. The reference fuel mass divided by the time interval is the reference fuel flow rate.
(5) Flow rates—inlet air, dilution air, diluted exhaust, raw exhaust, or sample flow. Use a reference flow meter with a blower or pump to simulate flow rates. Use a restrictor, diverter valve, a variable-speed blower or a variable-speed pump to control the range of flow rates. Use the reference meter's response as the reference values.
(i) Reference flow meters. Because the flow range requirements for these various flows are large, we allow a variety of reference meters. For example, for diluted exhaust flow for a full-flow dilution system, we recommend a reference subsonic venturi flow meter with a restrictor valve and a blower to simulate flow rates. For inlet air, dilution air, diluted exhaust for partial-flow dilution, raw exhaust, or sample flow, we allow reference meters such as critical flow orifices, critical flow venturis, laminar flow elements, master mass flow standards, or Roots meters. Make sure the reference meter is calibrated by the flow-meter manufacturer and its calibration is NIST-traceable. If you use the difference of two flow measurements to determine a net flow rate, you may use one of the measurements as a reference for the other.
(ii) Reference flow values. Because the reference flow is not absolutely constant, sample and record values of n refi for 30 seconds and use the arithmetic mean of the values, n ref, as the reference value. Refer to §1065.602 for an example of calculating arithmetic mean.
(6) Gas division. Use one of the two reference signals: (i) At the outlet of the gas-division system, connect a gas analyzer that meets the linearity verification described in this section and has not been linearized with the gas divider being verified. For example, verify the linearity of an analyzer using a series of reference analytical gases directly from compressed gas cylinders that meet the specifications of §1065.750. We recommend using a FID analyzer or a PMD/MPD O2 analyzer because of their inherent linearity. Operate this analyzer consistent with how you would operate it during an emission test. Connect a span gas to the gas-divider inlet. Use the gas-division system to divide the span gas with purified air or nitrogen. Select gas divisions that you typically use. Use a selected gas division as the measured value. Use the analyzer response divided by the span gas concentration as the reference gas-division value. Because the instrument response is not absolutely constant, sample and record values of xrefi for 30 seconds and use the arithmetic mean of the values x ref, as the reference value. Refer to §1065.602 for an example of calculating arithmetic mean.
(ii) Using good engineering judgment and gas divider manufacturer recommendations, use one or more reference flow meters to verify the measured flow rates of the gas divider.
(7) Continuous constituent concentration. For reference values, use a series of gas cylinders of known gas concentration or use a gas-division system that is known to be linear with a span gas. Gas cylinders, gas-division systems, and span gases that you use for reference values must meet the specifications of §1065.750.
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§ 1065.308 Continuous gas analyzer system-response and updating-recording verification.
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(a) Scope and frequency. Perform this verification after installing or replacing a gas analyzer that you use for continuous sampling. Also perform this verification if you reconfigure your system in a way that would change system response. For example, perform this verification if you add a significant volume to the transfer lines by increasing their length or adding a filter; or if you change the frequency at which you sample and record gas-analyzer concentrations.
(b) Measurement principles. This test verifies that the updating and recording frequencies match the overall system response to a rapid change in the value of concentrations at the sample probe. Gas analyzer systems must be optimized such that their overall response to a rapid change in concentration is updated and recorded at an appropriate frequency to prevent loss of information.
(c) System requirements. To demonstrate acceptable updating and recording with respect to the system's overall response, use good engineering judgment to select one of the following criteria that your system must meet:
(1) The product of the mean rise time and the frequency at which the system records an updated concentration must be at least 5, and the product of the mean fall time and the frequency at which the system records an updated concentration must be at least 5. This criteria makes no assumption regarding the frequency content of changes in emission concentrations during emission testing; therefore, it is valid for any testing.
(2) The frequency at which the system records an updated concentration must be at least 5 Hz. This criteria assumes that the frequency content of significant changes in emission concentrations during emission testing do not exceed 1 Hz.
(3) You may use other criteria if we approve the criteria in advance.
(4) For PEMS, you do not have to meet this criteria if your PEMS meets the overall PEMS check in §1065.920.
(d) Procedure. Use the following procedure to verify the response of a continuous gas analyzer system:
(1) Instrument setup. Follow the analyzer system manufacturer's start-up and operating instructions. Adjust the system as needed to optimize performance.
(2) Equipment setup. Using minimal gas transfer line lengths between all connections, connect a zero-air source to one inlet of a fast-acting 3-way valve (2 inlets, 1 outlet). Using a gas divider, equally blend an NO–CO–CO2–C3H8–CH4 (balance N2) span gas with a span gas of NO2. Connect the gas divider outlet to the other inlet of the 3-way valve. Connect the valve outlet to an overflow at the gas analyzer system's probe or to an overflow fitting between the probe and transfer line to all the analyzers being verified.
(3) Data collection. (i) Switch the valve to flow zero gas.
(ii) Allow for stabilization, accounting for transport delays and the slowest instrument's full response.
(iii) Start recording data at the frequency used during emission testing. Each recorded value must be a unique updated concentration measured by the analyzer; you may not use interpolation to increase the number of recorded values.
(iv) Switch the valve to flowthe blended span gases. (continued)