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Section 6
Sensor setup
6.1 Downlook ultrasonic sensor
The sampler uses a 40 kHz Downlook Ultrasonic Sensor.
6.2 Downlook ultrasonic sensor connection
The downlook ultrasonic sensor connection is located on the left side of the sampler
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.
6.2.1 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, then press
ACCEPT
.
6.2.2 Downlook ultrasonic sensor calibration
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.
6.2.2.1 Liquid depth
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. Many flumes have specific requirements.
Level Depth calibration is primarily is 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).
Note: Always re-check the Level Adjust when re-installing 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.
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 also
recommends 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 the
surrounding ambient temperature. Press
ACCEPT
.
Goodnal STP ST041 Pre Treatment (Sigma 900 MAX All Weather Refrigerated Sampler) Vendor Manual
Q-Pulse Id VM373
Active 29/10/2013
Page 73 of 122
