Hach Sigma 950 Instrument Manual

Contents

Hach Sigma 950 Instrument Manual Manual pdf 55 page image

53Optional Device Installation7. Select another channel to configure or press RETURN to back up one step. Press theMAIN MENU function key to return to the Main Menu.7.4.3 Dissolved Oxygen Probe Temperature Programming1. From the Main Menu, select OPTIONS>ADVANCED OPTIONS>DATALOG2. Highlight Select Inputs using the UP and DOWN soft keys, thenpress SELECT.3. Highlight D.O. Temp. using the UP and DOWN soft keys, then press SELECT.4. Press CHANGE CHOICE to cycle between Logged and Not Logged, then pressACCEPT.5. Enter a logging interval using the numeric keypad, then press ACCEPT. Valid loggingintervals are shown on the status bar along the bottom edge of the display.6. Press CHANGE CHOICE to select the temperature units (°C, °F).Press ACCEPT.7.4.4 Dissolved Oxygen Probe CalibrationNote: The membrane of a charged sensor must be kept moist. If the membrane is allowed to drycompletely, the electrolyte film between the membrane and the platinum will evaporate, destabilizingthe sensor. If the sensor will be out of water for more than 30 minutes, put a small amount of water inthe silicon soaking cap, and install it over the protective guard. Lift the edge of the cap to break theseal as it is being removed. This will prevent a vacuum from forming inside the soaking cap while itis being removed which can result in the membrane becoming stretched.1. Connect a suitable power supply to the flow meter.2. Power up the unit by pressing the ON button.3. From the Main Menu, select OPTIONS > ADVANCED OPTIONS > CALIBRATION > DO.4. Enter the ambient air temperature (the current reading is displayed for reference)using the numeric keypad.5. Enter the elevation above sea level for the specific location.6. Enter the membrane thickness. The operation of the 950 Flow Meter will be affectedby the choice of membrane thickness for the oxygen sensor.7. For general purpose applications, the 1-Mil membrane is standard. This membraneallows measurements in the 0 to 20 ppm range of dissolved oxygen and provides thebest general purpose trade-off between response time and durability.8. The 2-Mil membrane can be used to measure up to 40 ppm of dissolved oxygen. Itsincreased thickness slows the response time of the sensor, but this membrane hasincreased resistance to cuts and tears. For this reason, it is recommended for use inwastewater aeration basins where solids in the water are in rapid motion.9. Enter the chlorinity (salinity) of the flow stream (typical wastewater is zero, sea wateris higher).10. Place the D.O. probe in open air and press any key. The 950 Flow Meter will wait forthe reading to stabilize before storing the calibration value. The screen willautomatically return to the calibration menu.Calibrating the D.O. Temperature1. Place the probe and the thermometer in a liquid.2. Wait for the temperature reading to stabilize, approximately 30 minutes.3. Enter the actual temperature of the liquid.