Hach Sigma 950 Instrument Manual

Contents

Hach Sigma 950 Instrument Manual Manual pdf 37 page image

35Sensor Installation3. Select Standard as the type of Ultrasonic Transducer using the CHANGE CHOICE softkey. Press ACCEPT to continue.Temperature Time ConstantThe speed of sound in air varies with the temperature of the air. The ultrasonic sensor isequipped with temperature compensation to help eliminate the effect of temperaturevariation under normal site conditions. The transducer must be equal to the ambient airtemperature at the site prior to calibration for optimum results. The manufacturer alsorecommends that sensors be shielded from direct sunlight for this reason.4. Enter the ambient air temperature at the transducer location. For optimum results,allow enough time (100 minutes) to ensure that the sensor is at equilibrium with thesurrounding ambient temperature. Press ACCEPT to continue.5. Select the Liquid Depth method and enter the new level.6. Take a physical measurement of the liquid depth and enter the value.7. Press ACCEPT when finished.6.1.3.2 Sensor HeightThis method requires you to enter the distance between the face of the ultrasonic sensorand the zero flow point in the primary device. The zero flow point in a primary device isthe level at which flow ceases. In a round pipe the zero flow point would typically be theinvert or bottom of the pipe. In a V-notch weir the zero flow point occurs when the liquidbehind the weir is level with the bottom of the ‘V’. (There would still be liquid behind theweir plate but it would not be contributing to flow). Sensor Height calibration is generallyused when access to the primary device is difficult (such as confined space entry in amanhole) or there is no liquid flowing during installation of the flow meter.1. From the Main Menu, select OPTIONS>ADVANCEDOPTIONS>CALIBRATION>ULTRASONIC SENSOR.2. Select Calibrate U-Sonic using the UP and DOWN soft keys. Press SELECT.3. Select Standard as the type of Ultrasonic Transducer using the CHANGE CHOICE softkey. Press ACCEPT to continue.4. Enter the ambient air temperature at the transducer location. For optimum results,allow enough time (100 minutes) to ensure that the sensor is at equilibrium with thesurrounding ambient temperature. Press ACCEPTto continue.5. Select the Sensor Height method and enter the new level.6. Enter the distance from the face of the transducer to the zero flow point of theprimary device.7. Press ACCEPT when finished.6.1.3.3 Setting the Invisible Range1. From the Main Menu, select OPTIONS>ADVANCEDOPTIONS>CALIBRATION>ULTRASONIC SENSOR.2. Select the Invisible Range option using the UP and DOWN soft keys. Press SELECT tocontinue.3. Enter the Distance to End of the Invisible Range using the keypad.4. Select either inches or centimeters using the CHANGE UNITS soft key. The distancemust be greater than the minimum deadband of 25.4 cm (10 in.) for the 75 kHzsensor and 38.1 cm (15 in.) for the 50 kHz sensor.5. Press ACCEPT when finished.