Hach 900 MAX manual Sensor Setup, Downlook Ultrasonic Sensor Connection, Section

Section 4 Sensor Setup

4.1 Downlook Ultrasonic Sensor

4.1.1 Downlook Ultrasonic Sensor Connection

The downlook ultrasonic sensor connection is located on the back side of the refrigerated cabinet. The gray rectangular box houses the ultrasonic module and the transducer connector labeled ULTRASONIC. The connector is keyed and can only be inserted in the proper orientation (key up).

4.1.2 Downlook Ultrasonic Sensor Programming

The downlook ultrasonic sensor does not require specific programming, unless more than one sensor option is connected to the sampler. When more than one sensor option is connected to the sampler:

1.From the Main Menu, select OPTIONS>LEVEL SENSOR.

2.Select Ultra-Sonic using the CHANGE CHOICE key. Press ACCEPT.

4.1.3Downlook Ultrasonic Sensor Calibration

4.1.3.1 Liquid Depth

Note: Always re-check the

Level Adjust when re-installing the flow meter.

Calibrate the current water level via one of two methods; Liquid Depth or Sensor Height. An Invisible Range can also be set which allows the transducer to ignore reflections from obstructions between the sensor and the water surface, such as ladder rungs, channel side walls, etc. Each method has its own advantages and disadvantages; selecting the proper method will depend upon the site conditions. Calibrate the ultrasonic sensor each time the sensor is installed at a new site.

This method requires the level or depth of liquid in the channel that is contributing to flow. In a round pipe, the entire depth typically contributes to flow. In a weir, only the depth that is flow over the weir plate contributes to flow. Level Depth calibration is primarily used when:

•Access is available to the primary device for a physical measurement of the liquid depth, and

•When water is flowing during installation (channel is not dry).

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.

Temperature Time Constant

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. The transducer must be equal to the ambient air temperature at the site prior to calibration for optimum results. The manufacturer recommends that sensors be shielded from direct sunlight for this reason.

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