User manual HANNA INSTRUMENTS HI 8043

[. . . ] Dissolved oxygen is indicated in mg/l (ppm) and this value is compensated for the temperature effect (ATC). The dissolved oxygen probe has a membrane covering the polarographic sensors and a builtin thermistor for temperature measurements and compensation. The thin permeable mem3 brane isolates the sensor elements from the sample tested, but allows oxygen to enter. A voltage is applied across the sensor, and the oxygen that has passed through the membrane reacts causing the current to flow, hence determining a reading. [. . . ] The indications given by the instrument must fall to stabilization levels. If the probe has not been sufficiently polarized, the readout will continue to fluctuate. °C O2 STB OFF °C O2 · 9 · In this case, switch back STB °C O to "STB" position, place OFF the protective cap and wait for a few hours for complete polarization before proceeding. Using a small screwdriver, turn the Zero Calibration screw until the display reads zero. 2 ZERO SLOPE °C · If the zero point is passed, "1" will appear on the display. If you cannot get zero reading the probe is probably defective, in which case you should check the membrane, electrode and electrolyte solution (see below). Rinse the probe thoroughly with normal tap water after the zero calibration has been completed. SLOPE CALIBRATION: In order to perform a highly accurate calibration, take a B. O. D. bottle and then fill with water to a depth of 1 or 2 cm (½ or ¾"), then seal the bottle with the probe inside. If this calibration is to be carried out with the bottle opened to air rather than according to the conditions described above, the margin of error is approximately 0. 1 ppm. · Switch the instrument to "°C", wait for readings to stabilize and then note the temperature of the water. 10 STB OFF °C O2 · · Refer to Table 1 on page 10 for the corresponding dissolved oxygen reading at that temperature. Switch to "O2" position STB °C and adjust the "Slope" OFF O trimmer until the correct reading is displayed; e. g. at 20. 5°C the trimmer should be adjusted until display reads 9. 08. 2 ZERO SLOPE °C CORRECTION FOR ALTITUDE EFFECT If the calibration is not performed at sea level a correction should be made for the difference in altitude according to Table 2 on page 11; e. g. if calibrated at 20. 5°C at an altitude of 300 m above sea level, the display should be adjusted to 9. 08 x 0. 96 = 8. 72. ZERO SLOPE °C CORRECTION FOR SALINITY EFFECT Another correction has to be performed if the sample presents significant salinity concentrations. In such case, the reading has to be adjusted according to Table 3 on page 12; e. g. This is to ensure that the oxygen-depleted membrane surface is constantly replenished. To quickly check if the water speed is sufficient, wait for the reading to be stable and then move the D. O. If the reading is still stable, the measurement conditions are right, while if the reading increases the water movement is too low. During field measurements, this condition may be met by manually agitating the probe. During laboratory measurements, the use of a magnetic stirrer to ensure a certain velocity in the fluid is recommended. In this way, errors due to the diffusion of the oxygen present in the air in the solution are reduced to a minimum. At all times, the time necessary for thermal equilibrium to occur between the probe and the sample must be allowed (a few minutes for temperature difference of several degrees). 16 PROBE & MEMBRANE MAINTENANCE The oxygen probe body is made of reinforced plastic for maximum durability. A thermistor temperature sensor provides temperature measurements of the sample tested. It is always recommended that the protective cap be kept on the probe when the probe is not in use to provide protection against damage and dirt. [. . . ] If the repair is not covered by the warranty, you will be notified of the charge for repair or replacement. If the instrument is to be returned to Hanna Instruments, obtain a Return Goods Authorization from the Customer Service Department first and then send it with shipment cost prepaid. When shipping any instrument, make sure it is properly packaged for complete protection. All rights are reserved. Reproduction in whole or in part is prohibited without the written consent of the copyright owner. [. . . ]