Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:13:p44
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 13 (pt 44/56)
Character Range: 415816–418734

year.
9.4.5.3. Analytical balance
 The analytical balance used to determine the filter weight shall meet the linearity verification criterion of paragraph 9.2., Table 7. This implies a precision (standard deviation) of at least 2 µg and a resolution of at least 1 µg (1 digit = 1 µg).
 In order to ensure accurate filter weighing, it is recommended that the balance be installed as follows:
(a) Installed on a vibration-isolation platform to isolate it from external noise and vibration;
(b) Shielded from convective airflow with a static-dissipating draft shield that is electrically grounded.
9.4.5.4. Elimination of static electricity effects
 The filter shall be neutralized prior to weighing, e.g. by a Polonium neutralizer or a device of similar effect. If a PTFE membrane filter is used, the static electricity shall be measured and is recommended to be within
2.0 V of neutral.
 Static electric charge shall be minimized in the balance environment. Possible methods are as follows:
(a) The balance shall be electrically grounded;
(b) Stainless steel tweezers shall be used if PM samples are handled manually;
(c) Tweezers shall be grounded with a grounding strap, or a grounding strap shall be provided for the operator such that the grounding strap shares a common ground with the balance. Grounding straps shall have an appropriate resistor to protect operators from accidental shock.
9.4.5.5. Additional specifications
 All parts of the dilution system and the sampling system from the exhaust pipe up to the filter holder, which are in contact with raw and diluted exhaust gas, shall be designed to minimize deposition or alteration of the particulates. All parts shall be made of electrically conductive materials that do not react with exhaust gas components, and shall be electrically grounded to prevent electrostatic effects.
9.4.5.6. Calibration of the flow measurement instrumentation
 Each flowmeter used in a particulate sampling and partial flow dilution system shall be subjected to the linearity verification, as described in paragraph 9.2.1., as often as necessary to fulfil the accuracy requirements of this Regulation. For the flow reference values, an accurate flowmeter traceable to international and/or national standards shall be used. For differential flow measurement calibration see paragraph 9.4.6.2.
9.4.6. Special requirements for the partial flow dilution system
 The partial flow dilution system has to be designed to extract a proportional raw exhaust sample from the engine exhaust stream, thus responding to excursions in the exhaust stream flow rate. For this it is essential that the dilution ratio or the sampling ratio rd or rs be determined such that the accuracy requirements of paragraph 9.4.6.2. are fulfilled.
9.4.6.1. System response time
 For the control of a partial flow dilution system, a fast system response is required. The transformation time for the system