ISO 3405 Petroleum products - Determination of distillation characteristics at atmospheric pressure
8 Apparatus verification
8.1 Level follower
For automated apparatus, the level follower/recording mechanism of the apparatus shall have a resolution of 0.1 ml with a maximum error of 0.3 ml between the 5 ml and 100 ml points. The calibration of the assembly shall be verified according to the manufacturer's instructions at intervals of not more than 6 months.

NOTE The typical verification procedure involves verifying the output with the receiver containing 5 ml and 100 ml of material respectively.

8.2 Electronic temperature-measurement devices
Temperature-measurement devices using other than the specified mercury-in-glass thermometers shall exhibit the same temperature lag, emergent stem effect and accuracy as the equivalent mercury-in-glass thermometer. Verification of the calibration of these temperature sensors shall be carried out at intervals of not more than 6 months. The electronic circuit for resistance thermometers shall be verified against a standard precision resistance. When performing this verification, ensure that any algorithms used to correct the temperature for lag and emergent stem effect are not applied (see the manufacturer's instructions). The response of the temperature-measurement system itself shall also be verified by one of the procedures described in 8.2.1 or 8.2.2.
8.2.1 Distill reagent grade toluene in accordance with ISO 918 and compare the 50 % (V/V) recovered temperature with that shown by the above-mentioned mercury-in-glass thermometer when carrying out a manual test under the same conditions. Use reagent grade toluene for this test unless it can be shown that the grade proposed is of sufficient purity to permit its use without lessening the accuracy of the determination.

NOTE 1 For the purposes of this International Standard, the term "% (V/V)" is used to represent the volume fraction of a material.

Toluene is used as a verification fluid for bias; it will yield almost no information on how well an electronic measurement system simulates the temperature lag of a mercury-in-glass thermometer. Annex B describes a method to determine this difference in lag time.

NOTE 2 Toluene is shown in reference manuals as boiling at 110.6 °C under the conditions of ISO 918, which uses a partial immersion thermometer. Because this International Standard uses thermometers calibrated for total immersion, the results will be lower, and different for each. The approximate figures are 109.3 °C for the low-range thermometer, and 109.9 °C for the high-range thermometer.

8.2.2 Distill a certified reference fluid of a specific product group, under the manual conditions of this International Standard, using in sequence, the appropriate mercury-in-glass thermometer followed by the alternative temperature-measurement device or system. Record systematic deviations over the range of temperatures measured to ensure that no deviation exceeds the repeatability of this test method, and that the algebraic sum of the deviations is close to zero.

NOTE Certified reference fluids, consisting of specified mixtures of single compounds, are commercially available for group 1 and group 4 product types.