55Standard programs9. Select the required data analysis interval.It is possible to select a fixed interval and an specificcustomised interval with start and end dates.10. Press OK to confirm.11. Choose an upper and lower control limit for the first andsecond parameters and press Next to confirm.12. All of the selected functions are displayed in Ratio Settings.Press OK to confirm.13. Select the ratio with the defined settings from the ratiodirectory. Press Select.A table with the defined values is shown.Values outside the defined limits are displayed in red.5.3.4.3 Interference Check (not available on all models)The DR 3900 automatically tests for interfering ions. Typicalinterferences, such as chloride for nitrate, are recognised fromdefined concentrations and a warning is displayed. This check isonly carried out for barcode tests that are indicated with identicalsample IDs.
