User manual HANNA INSTRUMENTS C 125

[. . . ] 4 Principle of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] · At start-up the meter will show the full display for a few seconds, then changes to the measurement mode. · When the LCD displays "----" the meter is ready to measure. · Fill a clean cuvette up to 0. 5 cm (one quarter inch) from its rim with the thoroughly agitated sample. · Allow sufficient time for bubbles to escape before securing the cap. · Wipe the cuvette thoroughly with a lint-free tissue (HI731318) before inserting into the measurement cell. The cuvette must be completely free of fingerprints and other oil or dirt, particularly in the area where the light goes through (approximately the bottom 2 cm/1 inch of the cuvette). · Place the cuvette into the cell and check that the notch on the cap is positioned securely into the groove. · The mark on the cuvette cap should point towards the LCD. 8 · Press the READ/ key and the LCD will display a blinking "SIP" (Sampling In Progress). The limpidity value will appear after approximately 25 seconds. SOURCES OF INTERFERENCE · Presence of floating debris and coarse sediment which settle out rapidly will give false readings. · The infrared light source used for C125 limpidity meter can effectively minimize errors due to coloured dissolved substances. This effect, named "true colour", is a common interference for most commercially available instruments operating in the range of visible light. · Air bubbles and the effect of vibrations that disturb the surface of the sample will give false results. · Dirty glassware could also affect readings along with scratched or edged cuvette. 9 CALIBRATION If repeated measurements differ more than an acceptable value, check if the meter calibration status by measuring a standard solution. Anyway, it is recommended to perform a monthly calibration of the meter, or more frequently for greatest accuracy. To check the date of last calibration, press and hold the DATE/ key down for few seconds. CALIBRATION PROCEDURE · Turn the meter on and wait for the display to show "----". · Press the CAL key once, the "CAL" message will blink on the display for about 6 seconds, then the calibration mode stops. · While the "CAL" message is still blinking, press CAL again. The instrument is now in the calibration mode and a "CL" will appear on the lower part of the display. The date of calibration can be edited now by simply pressing the DATE/ key. The first blinking parameter is the month, on the left hand of the display (MM. DD). · To confirm the displayed data values and to go to the next step, press the CAL key once. [. . . ] Do not shake (to prevent air bubbles) and do not let the sample settle. · Rinse the cuvette twice with 5 ml of the liquid to be tested for removing the effect of dust or any previous liquid. Gently pour the liquid down the side of the cuvette to reduce air bubbles. · Before inserting the cuvette into the instrument, wipe it with soft, lint-free tissue. [. . . ]