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Downlook Ultrasonic Sensor
Section 4
4.10.3 Programming the Downlook Ultrasonic Sensor
The downlook ultrasonic sensor does not require specific programming,
unless more than one sensor option is connected to the 980 Flow Meter.
When more than one sensor option is connected to the 980 Flow Meter:
1. From the Main Menu, select
OPTIONS > LEVEL SENSOR
2. Select Ultra-Sonic Sensor using the CHANGE CHOICE soft key, then press
the
ACCEPT soft key.
4.10.4 Calibrating the Downlook Ultrasonic Sensor
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.
4.10.4.1 Liquid Depth
This method requires the “head” 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, refer to Working with Primary
Devices on page 109. 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 of the 980 Flow Meter (channel
is not dry).
Transducer Ringing
(False return echoes mask
“real” echoes)
Try moving the transducer farther from the liquid.
Check the area under the transducer for obstructions. This includes the area in front and to
the sides of the transducer.
Check the face of the transducer for a coating. This is rare, but cleaning the transducer face
may correct the problem. If this is a constant problem due to site conditions, coat the face of
the sensor with a thin film of silicone grease to keep debris from clinging.
Make sure that you are using the proper rubber isolation washers on the mounting bracket.
The transducer can resonate against steel mounting rails. See Mounting the Ultrasonic
Sensor on page 81.
RS485 Time Out
(Flow meter did not receive
data within the specified time)
If the CPU is having trouble communicating with the velocity board, RS485 time outs may
occur. Wait a few minutes and see if it goes away. If it continues, a problem with the ultrasonic,
velocity, or CPU board may exist.
May be caused by difficulty getting a good velocity reading. If the logging interval is 1 or 2
minutes, conditions are poor, and the problem continues indefinitely, try increasing the logging
interval to capture more signals.
This condition may occur occasionally. When using a combination of area velocity and
ultrasonic sensors, this condition may occur more frequently if site conditions are less than
ideal. This is not necessarily an indication of a defective sensor.
Check to see if wires were shorted. Check the RS485 fuse.
Problem/Error Message Possible Causes and Solutions