ASTM D4308 Test Method for Electrical Conductivity of Liquid Hydrocarbons by Precision Meter
13. Report
13.1 The report is to include the following:
13.1.1 The calculated conductivity of the sample in pS/m after correcting for the zero reading. Note MANUAL or AUTO mode.
13.1.2 Temperature of sample.
NOTE 8 - It is recognized that the electrical conductivity of a fuel varies significantly with temperature and that the relationship differs for various types of aviation and distillate fuel. If it is necessary to correct conductivity readings to a particular temperature, each laboratory would have to establish this relationship for the fuels and temperature range of interest.
14. Precision and Bias
14.1 The precision of this test method obtained by statistical examination of test results in the range between 0.1 and 2000 pS/m by operator/instrument pairs at a common test site is described in 14.2 and 14.3.
NOTE 9 - The data used to determine the precision of this test method were obtained using the auto mode.
14.2 Repeatability - The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test samples would, in the long run, in the normal and correct operation of the test method, exceed the values in Fig. 3 in only one case in twenty.
14.3 Reproducibility - The difference between two single and independent results obtained by different operators working at the same location on identical test materials would, in the long run, exceed the values in Fig. 3 only in one case in twenty.
14.3.1 In the event of a dispute or concern regarding shipped sample conductivity, it is recommended that operators come to the bulk hydrocarbon storage site to measure conductivity on freshly obtained samples according to the cited procedure. This ensures that samples identical to bulk storage are tested by either or both parties and the precision data in Fig. 3 shall apply (Note 10).
NOTE 10 - In 1987, a test program using Test Method D2624 was carried out to investigate reproducibility of results when samples are shipped between laboratories. 10 While repeatability values were similar to those from common site testing, it was concluded that adequate reproducibility values were not obtained due to changes in conductivity of samples during shipment and storage. The same possibility of conductivity change would occur for samples tested according to Test Method D4308.
14.4 Bias - Since there is no accepted reference material suitable for determining the bias of the procedure in Test Method D4308 for measuring conductivity, bias cannot be determined.
