Hach 900 MAX manual Section, Sensor Height, 4.1.3.3Setting the Invisible Range

Section 4

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 the surrounding ambient temperature. Press ACCEPT.

5.Select the Liquid Depth method and enter the new level.

6.Take a physical measurement of the liquid depth (level) and enter the value. Press ACCEPT when finished.

4.1.3.2 Sensor Height

This method requires entering the distance between the face of the ultrasonic sensor and the zero flow point in the primary device. The zero flow point in a primary device is the level at which flow ceases. In a round pipe the zero flow point would typically be the invert or bottom of the pipe. In a V-notch weir the zero flow point occurs when the liquid behind the weir is level with the bottom of the ‘V’. (There would still be liquid behind the weir plate but it would not be contributing to flow). Sensor Height calibration is generally used when:

•Access to the primary device is difficult (such as confined space entry in a manhole) or

•There is no liquid flowing during installation of the flow meter

1.From the Main Menu, select OPTIONS>ADVANCED

OPTIONS>CALIBRATION>ULTRASONIC SENSOR.

2.Select Calibrate U-Sonic using the UP and DOWN keys. Press SELECT.

3.Select Standard as the type of Ultrasonic Transducer using the CHANGE CHOICE key. Press ACCEPT to continue.

The speed of sound in air varies with the temperature of the air. The ultrasonic sensor is equipped with temperature compensation to help eliminate the effect of temperature variation under normal site conditions.

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 the surrounding ambient temperature. Press ACCEPT.

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 the primary device.

7.Press ACCEPT when finished.

4.1.3.3Setting the Invisible Range

1.From the Main Menu, select OPTIONS>ADVANCED

OPTIONS>CALIBRATION>ULTRASONIC SENSOR.

2.Select the Invisible Range option using the UP and DOWN keys. Press SELECT to continue.

3.Enter the Distance to End of the Invisible Range.

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