Document ID: chunk:federal_register_of_legislation:F2023L00129:reg:13:p46
Version: federal_register_of_legislation:F2023L00129
Segment Type: reg
Provision Reference: reg 13 (pt 46/56)
Character Range: 420956–423575

of the difference shall be such that the accuracy of qmp is within 5 per cent when the dilution ratio is less than 15. It can be calculated by taking root-mean-square of the errors of each instrument.

 Acceptable accuracies of qmp can be obtained by either of the following methods:

(a) The absolute accuracies of qmdew and qmdw are 0.2 per cent which guarantees an accuracy of qmp of  5 per cent at a dilution ratio of 15. However, greater errors will occur at higher dilution ratios;
(b) Calibration of qmdw relative to qmdew is carried out such that the same accuracies for qmp as in (a) are obtained. For details see paragraph 9.4.6.3.;
(c) The accuracy of qmp is determined indirectly from the accuracy of the dilution ratio as determined by a tracer gas, e.g. CO2. Accuracies equivalent to method (a) for qmp are required;
(d) The absolute accuracy of qmdew and qmdw is within 2 per cent of full scale, the maximum error of the difference between qmdew and qmdw is within 0.2 per cent, and the linearity error is within 0.2 per cent of the highest qmdew observed during the test.
9.4.6.3. Calibration of differential flow measurement
 The flowmeter or the flow measurement instrumentation shall be calibrated in one of the following procedures, such that the probe flow qmp into the tunnel shall fulfil the accuracy requirements of paragraph 9.4.6.2.:

(a) The flowmeter for qmdw shall be connected in series to the flowmeter for qmdew, the difference between the two flowmeters shall be calibrated for at least five set points with flow values equally spaced between the lowest qmdw value used during the test and the value of qmdew used during the test. The dilution tunnel may be bypassed;

(b) A calibrated flow device shall be connected in series to the flowmeter for qmdew and the accuracy shall be checked for the value used for the test. The calibrated flow device shall be connected in series to the flowmeter for qmdw, and the accuracy shall be checked for at least five settings corresponding to dilution ratio between 3 and 50, relative to qmdew used during the test;

(c) The transfer tube (TT) shall be disconnected from the exhaust, and a calibrated flow-measuring device with a suitable range to measure qmp shall be connected to the transfer tube. qmdew shall be set to the value used during the test, and qmdw shall be sequentially set to at least five values corresponding to dilution ratios between 3 and 50. Alternatively, a special calibration flow path may be provided, in which the tunnel is bypassed, but the total and diluent flow through the corresponding meters as in the actual