OTT SLD Series User manual
English
Quick Reference
Side Looking Doppler
OTT SLD
We reserve the right to make technical changes and improvements without notice.
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Table of contents
1 System description 5
2 Parts supplied/components of the OTT SLD 6
3 Preparing for installation 7
3.1 Installing the operating software 7
3.2 Cable connection 7
3.3 Checking the communication 8
3.4 Programming the datalogger 8
4 Installation 9
4.1 Calibrating the pressure sensor 9
4.2 Setting the operating parameters 10
4.3 Aligning the sensor 15
4.4 Checking the water level 17
4.5 Checking the range 17
5 Operation 19
5.1 Disconnecting the PC from the sensor 19
5.2 Connection to datalogger 20
5.3 Verifying the data 21
Appendix A 22
A.1 Technical data 22
A.2 Information on electromagnetic compatibility 23
A.3 Firmware update 23
Appendix B – SDI-12 commands and responses 24
B.1 Basic commands 24
B.2 Advanced commands 30
Appendix C – OTT SLD and Modbus fieldbus protocol 31
Appendix D – Representation of the accumulated discharge volumes 34
D.1 Representation in SDI-12 protocol 34
D.2 Representation in Modbus protocol 35
Appendix E – Installation examples 36
E.1 Example #1 – Installation at a staircase for water level measurement
(mounting rail with slide) 37
E.2 Example #2 – Installation at a staircase for water level measurement
(dual T rail with roller slide) 38
E.3 Example #3 – Installation at a natural river bank slope
(mounting rail with slide) 39
E.4 Example #4 – Installation at a vertical edge wall
(mounting rail with slide) 40
E.5 Example #5 – Installation on a concrete base in the river bed 41
E.6 Example #6 – Installation at a sheet pile 42
E.7 Example #7 – Installation at a vertical edge wall (mounting plate) 43
1 System description
During installation, the sensor is connected to the PC and parameterized using a
serial interface (a). After completing the installation, serial communication is termi-
nated. Thereafter, the sensor is controlled from the datalogger through SDI-12 or
RS-422/RS-485 (b) (SDI-12 protocol).
a) Sensor – Cable – PC/power supply
b) Sensor – Cable – Datalogger/power supply
Fig. 1: Schematic diagram of the
wiring configuration used for setting
the operating parameters.
Fig. 2: Schematic diagram of the wiring
configuration used for measuring.
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2 Parts supplied/components of the OTT SLD
Please check the contents of the shipping crate against the packing list supplied.
The sensor specification may be obtained from the name plate.
Basically, the OTT SLD scope of supply includes 3 items:
Connection cable
Sensor
Operating software CD
The following instrument versions are available:
Discharge
– Measured variables: Flow velocity and water level;
– Built-in discharge calculation;
– Frequencies: 600 kHz, 1.0 MHz, or 2.0 MHz;
– Design: Horizontal or vertical type;
– Interfaces: RS-232 and SDI-12 or RS-422/RS-485 (SDI-12 protocol).
Velocity (flow velocity)
– Measured variable: Flow velocity;
– Frequencies: 600 kHz, 1.0 MHz, or 2.0 MHz;
– Design: Horizontal or vertical type;
– Interface: RS-232 and SDI-12 or RS-422/RS-485 (SDI-12 protocol).
Fig. 3: Components of the OTT SLD.
1 – Sensor head
2 – Sensor housing
3 – End piece with connector socket
The figure shows the "Discharge" instrument
version (measured variable: flow velocity
and discharge); Frequency: 1.0 MHz;
horizontal installation; RS-422/RS-485
interface (SDI-12 protocol).
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3 2 1
3 Preparing for installation
This chapter covers preparing the installation and may be carried out in office.
Within the operating software menus, please use dots instead of commas as
decimal separators (e.g. 1.5m for one and a half meters).
3.1 Installing the operating software
The software is run on the Microsoft Windows XP®operating system or later.
Insert the CD-ROM into the CD drive. Start the "setup.exe" file. Follow the instruc-
tions displayed.
3.2 Cable connection
There are 2 cable options.
a) RS-232 in combination with SDI-12 (maximum 65m);
b) RS-422/RS-485 (SDI-12 protocol) (maximum 500m).
The cables have a coded underwater connector.
Spray the contact pins of the connector and the socket with a silicone spray.
Use the "Scotch™ 1609" silicone spray manufactured by "3M" for this
purpose. Each time you subsequently establish an electrical connection, you
must spray again!
Attach the connector to the plug on the sensor. Secure the connection by
tightening the cap nut (manually – don't use a tool).
The second cable end is open. For communication with your PC, you can
temporarily attach the sub-D socket (9-pin) provided for this open end.
Connect this to your PC's serial interface (possibly RS-232/use a USB adapter).
Connect "+ Supply" to the positive pole and "GND Supply" to the negative
pole of your 12V power supply.
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0
RS-232
Supply + Supply (typ. +12 V)
GND
SDI-12
RS-232
Not used
OTT SLD
Shielding
RS-232 Rx
RS-232 Tx
SDI-12 Data
SDI-12 GND
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0
OTT SLD
RS-422
Supply + Supply (typ. +12 V)
GND
Not used
RS-422
RS-422
Shielding
RS-422 Tx–
RS-422 Tx+
RS-422 Rx+
RS-422 Rx–
Fig. 5: RS-422 connection diagram.
Fig. 4: RS-232 connection diagram.
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Please note:
Never grease the contact pins. Risk of corrosion!
Never pull on the cable when disconnecting the connector from the plug!
Handle the connector with care! Avoid unnecessary long-term exposure to
sunlight!
Avoid placing tensile load on the cable!
Do not bend the cable!
Recommendation: Check the connection on a regular basis.
3.3 Checking the communication
Start the OTT SLD EasyUse Software.
From the "Communication" menu, select the "Serial Port" option.
Select "OK" to confirm the "9600" option of the "Baud rate" item.
From "Communication", select the "Connect" option. Now your PC is con-
nected to the sensor.
3.4 Programming the datalogger
Configure your datalogger (refer to the OTT netDL/OTT DuoSens Operating
Instructions). In Appendix B, all SDI-12 commands of the OTT SLD are described.
Make sure that the SDI-12 address of the datalogger matches the SDI-12 address
of the OTT SLD.
Please note: For an OTT SLD "Discharge" instrument version in combination
with an OTT DuoSens, discharge calculation must be performed in the OTT SLD!
There is no option for creating a configuration for calculating the discharge within
the OTT DuoSens.
Fig. 6: Selecting the serial port.
Fig. 7: Setting the baud rate.
Fig. 8: Connection test is successful.
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4 Installation
Please note: Install the OTT SLD in such a way that it will be immersed in water
under any operating conditions. In case this cannot be ensured, provide suitable
equipment for automatically disconnecting the operating voltage when the unit is
"falling dry". Only thus, safe and trouble-free operation of the OTT SLD will be
ensured.
Route the cable from the place of installation of the sensor to the location of the
datalogger. Now repeat all steps described in Chapter 3.
4.1 Calibrating the pressure sensor
The pressure sensor is available only in combination with water level measurement
("Discharge" instrument version).
Calibrate the pressure sensor at the place of installation. The sensor may be
calibrated when it is inside or outside the water.
Perform the following steps:
From the "On-line" menu, select the "Set Pressure Offset" option.
Set the present water coverage of the sensor (outside the water: 0m).
Select "OK" to confirm. The pressure sensor will be calibrated now.
Fig. 9: Set pressure offset.
Fig. 10: Setting the offset.
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4.2 Setting the operating parameters
When you want to create a completely new parameterization,
– select the "Deployment planning"option from the "Deployment" menu;
– select "Load From Instrument", when you want to use the configuration stored
in the sensor.
Select the "Standard" tab and parameterize the following boxes:
Sensor :
Frequency Select the acoustic frequency of the sensor.
Enter the measurement interval. The measurement interval is
triggered by the sensor during serial communication only.
When a datalogger is connected (SDI-12 protocol), this inter-
val is controlled by it. In such a case, leave the measurement
interval of 300 seconds unchanged! Minimum measurement
interval [s] = Flow average interval [s] + Level average
interval [s] + 5 s
River bank Select the river bank side (in flow direction) at which the OTT
SLD is installed: "Left" or "Right". The OTT SLD is designed to
be installed at the right-hand bank side of a flowing water-
way. When it is installed on the left-hand bank side, it will
provide negative flow velocities because of its design. When
"Left" is selected, the OTT SLD will change the sign of the
negative flow velocities the absolute amount of which is,
however, correct.
Fig. 11: "Deployment" menu.
Measurement
interval
Fig. 12: "Deployment Planning"
option, "Standard" tab.
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Flow:
Average interval Enter the averaging interval for velocity measurement.
The recommended values are 60s (30s (high flow
velocities above 1m/s) …120s (low flow velocities up
to approx. 0.3m/s).
Cell size Enter the cell size (refer to Fig. 13).
Blanking distance Enter the blanking distance (refer to Fig. 13).
Ship/Vessel filter:
The ship filter is able to detect ships passing the measuring station. To this end, the
OTT SLD uses a mathematical algorithm to compare the signal amplitudes of the
echoed signals in measuring cells that may be selected. When no ship is passing the
measuring station, the signal amplitudes are continuously decreasing with increasing
distance to the OTT SLD. When a measuring cell has a signal amplitude caused by
reflection at an object that is significantly higher than that of the previous signal, this
is considered to be an indication of a ship passing by. In such a case, the OTT SLD
will retain the previous measured value for an adjustable period of time.
Please note: The ship filter is available only for the „Discharge“ instrument version
and with the „Discharge“ checkbox selected (see Fig. 15)! In any other case the
boxes for setting parameters are dimmed.
Tolerance Responsiveness of the ship filter.
Recommendation for setting the value: During commission-
ing, set the slider to the center position between "Low" and
"High". Thereafter, use the on-line measurement window
to check whether the ship filter is responding appropriate-
ly. As necessary, move the slider in the "Low" direction
(ship filter has detected a ship passing by although there
is only flotsam), or move the slider in the "High" direction
(ship filter has not detected that a ship is passing by).
Hold old value for [s] Time in seconds the OTT SLD will retain the previous
value after the ship filter has detected a ship passing by.
Message shown in the online measurement window:
"Ship filter holding".
Start Cell First measuring cell in which the ship filter is active;
End Cell Last measuring cell in which the ship filter is active.
From the defined measured volume, select the range in
which ships may actually pass by.
OTT SLD
Cell size
Blanking
Cell 1 Cell 2 Cell 3 Cell 4 Cell 5 Cell 6 Cell 7 Cell 8 Cell 9
Fig. 13: Schematic diagram for
"Cell size" and "Blanking".
Fig. 14: Available status messages of the
ship filter (On-line measurement window).
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Level:
Average interval Enter the averaging interval for the water level measure-
ment. The recommended value is 15s (up to 30s).
Quality threshold Enter a value for the quality lower limit of the water level
measurement. The optimum setting is between 80 and 120.
Alternatively, you can also enter "0". In this case the
OTT SLD determines the value for the lower quality limit
for each measurement independently (recommended pro-
cedure). Detailed information can be found in chapter4.4.
Caution: For sensors without water level measurement (instrument version:
"Velocity"; refer to Chapter 2), the "Level" checkbox must not be selected.
Speed of sound parameter:
The speed of sound in water depends on its density. The density itself is influenced
by the temperature and the salinity of the water. The OTT SLD calculates the flow
velocity of a water body based on the speed of sound. There are two ways to do
this:
Measured salinity The OTT SLD compensates the speed of sound (reference
velocity: 1500 m/s at 20 °C and 0 ppt) on the basis of
the currently measured water temperature and the entered
salt content. You have to measure the salt content once
on site and enter it in the unit ppt (parts per thousand;
1 ppt ≈ 1 g/l). If the salt content is not known, enter "0".
The OTT SLD then calculates on the basis of pure water.
(The influence of the salt content on the speed of sound is
clearly smaller than the influence of the temperature).
Fixed There is no compensation of the speed of sound based on
the water temperature and the salt content. The OTT SLD
calculates the flow velocity based on the set speed of
sound. With this setting, strong fluctuations of the water
temperature and the salt content inevitably lead to a higher
inaccuracy of the flow velocity.
Deployment planning:
Power consumption Reflects the energy consumption in Wh per day.
Power level – Flow This parameter is set by the OTT SLD.
Default: "HIGH".
Power level – Level This parameter is set by the OTT SLD.
Default: "LOW".
For "Discharge" instrument version: Select the "Discharge" tab.
Select the "Discharge" checkbox and parameterize the following boxes:
Discharge:
Total volume interval Interval in hours that the OTT SLD uses to determine
the accumulated discharge from individual Q values.
Value range: 1 … 24 hours.
Start Cell The first measuring cell the OTT SLD uses for discharge
calculation. (Example based on the result of the range
check of Fig. 23: Cell #1).
End Cell The last measuring cell the OTT SLD uses for discharge
calculation. (Example based on the result of the range
check of Fig. 23: Cell #4).
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k*A Table:
Data pairs for "Water level" and corrected areas
"k*A". You may manually enter individual data pairs
or load them into the operating software as a complete
table (refer to the "Import Prodis 2 k*A table" button).
Loads a complete table into the operating software that
was created using the OTT Prodis 2 calibrating soft-
ware. File format: "*.XML".
Please note:
The k*A table created must match the cells used! When the OTT SLD e.g. uses
the cell numbers 3 through 7 for discharge calculation, the k*A table must also
have been created based on these cells.
To set the reference height of the OTT SLD water level sensor later (see
Figure 17), you must first prepare the k*A table generated by OTT Prodis 2:
Open the table (file format: "*.XML") with any text editor; e.g. with the
"Notepad" from Microsoft (included with the operating system).
Delete the line "<zeropointlevel>...</zeropointlevel>" completely; see
Figure 16. Do not make any further changes to the file.
Save the file. You can then import the table using the "Import Prodis 2 k*A
table" function.
Fig. 15: "Deployment Planning"
option, "Discharge" tab.
Water level [m]
k*A [m2]
Import Prodis 2
k*A table
Fig. 16: Prepare OTT Prodis 2
k*A table.
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Using the settings made in this window, the OTT SLD calculates the discharge "Q"
from the flow velocity measured as well as from the table values for water level
and corrected areas (k*A) ("Q" calculation based on the index method). More-
over, the OTT SLD uses the Q values calculated to determine an accumulated
discharge value over a selectable period of time. Between two measurement
intervals, the discharge is assumed to be constant.
Example
– Measurement interval: 5 minutes (300 seconds)
– Accumulating interval: 1 hour
QAccum. = Q1x 300 + Q2x 300 + … + Q11 x 300 + Q12 x 300
Within one accumulating interval, the accumulated discharge QAccum will increase
with every measurement interval. At the beginning of a new accumulating interval,
the OTT SLD will reset this value to zero.
Set the reference height of the OTT SLD water level sensor:
– When the k*A table used is based on the "coverage" of the water level
sensor (OTT SLD ↔water surface distance) ➝ Enter "0".
– When the k*A table used is based on another reference point (e.g. "above
mean sea level") ➝ Enter the distance from the reference point to the water
level sensor.
Select the "OK" button.
Do not start the online data collection: Select the "No" button.
When you want to change the parameterization at a later time, data collection
must be stopped! Then proceed as described in this section.
Fig. 17: Entering the reference height for
the OTT SLD water level sensor.
Fig. 18: Starting the on-line data collection.
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4.3 Aligning the sensor
Attach the sensor to the bracket. Position the sensor in the water as desired. To
check proper operation of the sensor, the sensor head must be within the water.
The pressure cell requires a minimum water coverage of 15cm. Ensure that there
are no obstructions in the water that may affect sensor operation. Perform the
alignment test as follows:
From the "On-line" menu, select the "Start Level Check" option.
In the lower left corner of the window, "Tilt", „"Pitch", and "Roll" are displayed.
Move the sensor so that "OK" will be shown for "Tilt". Fix the sensor in this position.
Fig. 19: Starting the level check.
Fig. 20: "Level check" evaluation window.
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0°
0°
z
x
Roll
Roll = Roll angle in x axis
Pitch = Tilt angle in y axis
y
Pitch
positive pitch/roll values* (OTT SLD rotated clockwise)
OTT SLD horizontal instrument versionOTT SLD vertical instrument version
negative pitch/roll values* (OTT SLD rotated counter-clockwise)
z
x
Roll
y
Pitch
When installing the OTT SLD, align it such that the “Tilt”** value is within the range of -3° … +3° (“Tilt: OK”)
(Tilt = Pitch
2
+ Roll
2
)
*
Value range: ±25° (shown in gray, beyond this value, the OTT SLD will set bit 3/ bit 4 in status value to “1”
**
Refer to “Level Check” window (“On-line” menu) in OTT EasyUse software
+
+
+
+
Fig. 21: Pitch/Roll values when aligning the OTT SLD.
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4.4 Checking the water level
The water level is determined by evaluating the runtime an acoustic signal takes
from the sensor to the water surface and back. Runtime measurement is supported
by a pressure sensor.
Figure 20 shows the strength of the amplitude (green) and the quality (yellow) of
the received (reflected) signal in the horizontal axis. The vertical axis shows the
distance of the water surface to the sensor. The dashed horizontal white line
shows the water surface height determined by the pressure sensor, and the purple
line shows the water surface height measured by the acoustic sensor. The sensor
takes into account only those values that are within ±30cm of the pressure sensor
value (red dashed lines).
Furthermore, the screen shows information on the alignment of the sensor at the
bottom left-hand side (refer to Chapter 4.3), the water temperature in °C (degC)
and water depth (Level) in the bottom center, and the value of the pressure sensor
(Pressure) as well as the combined water level (Level (P)) at the bottom right-hand
side. The combined water level includes the pressure and acoustic sensors to avoid
incorrect measurements caused by e.g. reflections. For further calculations, the
combined water level is recommended to be used.
Figure 20 shows 3 significant amplitudes at approx. 65cm, 130cm, and
195cm. This is an indication of multiple reflections. In the "Deployment" dialog,
set the threshold (Threshold – the red vertical line in the Figure) so that the quality
and amplitude values corresponding to the present water height will exceed the
threshold. Any values below the threshold will not be included in the calculation.
Complete the test: From the "On-line" menu, select the "Stop Data Collection"
option.
4.5 Checking the range
The range check is to ensure that the flow velocity is gathered in an optimum way.
It helps identify underwater obstructions and adapt the size of the measuring cell
and the blanking distance to the river geometry. Figures 23 and 24 show the dis-
tance from the sensor and the position of the measuring cells in the horizontal axis
and the strength of the received (reflected) signal in the vertical axis.
From the "On-line" menu, select the "Start Range Check" option.
The following figures show typical curves obtained from range checks. To get a
better overview, you may remove individual curves by disabling the respective
checkboxes ([X] ➝[ ]). It is recommended to display beams 1 and 2 only (disable
beams 3 and 4).
Fig. 22: Starting the range check.
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Figure 23 shows a test that provides an optimum result. For both acoustic beams,
the strength of the echo signal continuously decreases over the entire distance. The
increase obtained in cell #5 is caused by reflections from the opposite bank.
Therefore, only cells #1 through #4 should be used.
Please make sure that the last cell of the measured value ends at 80% of the
waterway width (based on the width in the mounting height of the sensor) to pre-
vent interference from the opposite bank affecting the signal evaluation.
The red area in Figure 24 identifies those cells in which the reflected signal is too
weak to be evaluated. That means that even cell #5 does not provide usable data.
Furthermore, signal amplifications at 2.5 m and 10 m are indications of interfer-
ence (e.g. obstructions).
Complete the test: From the "On-line" menu, select the "Stop Data Collection"
option.
Fig. 23: Successful range check.
Fig. 24: Range check failed.
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5 Operation
After completing all tests to be done during installation, the sensor is ready for use.
5.1 Disconnecting the PC from the sensor
Check whether the datalogger measurement interval is larger than the averaging
interval of the flow or level measurements (for the formula, refer to Chapter 4.2).
From the "Deployment" menu, select the "Start SDI-12 Mode" option.
Set the sensor address. The default address is "0". When the sensor is fitted
with an RS-422 interface, select "SDI-12 over RS-485".
Select the "Start" button.
Save the configuration to your PC.
Fig. 25: Starting SDI-12.
Fig. 26: Setting the SDI-12 address.
Fig. 27: Saving the deployment.
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In the subsequent window, the final parameterization of the sensor is dis-
played. Please check it carefully. Use the "Confirm" button to confirm the
configuration.
Now you have successfully configured the OTT SLD.
Use the "OK" button to disconnect the connection to the PC.
Also, physically disconnect the connection to the PC.
5.2 Connection to datalogger
Connect the sensor to the OTT netDL/OTT DuoSens using the SDI-12 interface
(refer to the OTT netDL/OTT DuoSens Operating Instructions).
Fig. 28: Confirming the deployment.
Fig. 29: SDI-12 started.
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4312
SDI-12 Data
SDI-12 GND
+ 12 V
GND
OTT DuoSens/
OTT netDL screw
terminal A/C
OTT SLD
RS-232
Supply
SDI-12
RS-232
Not used
Shielding
Fig. 30: Connecting the OTT SLD to
OTT DuoSens/OTT netDL using
the SDI-12 interface.
The GND connection represented by the
dashed line is necessary only in case the
OTT SLD/OTT netDL, and the OTT DuoSens
are powered by separate power supplies.
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