OTT SVR 100 User manual

English
Operating Instructions
Surface Velocity adar
OTT SV 100

We reserve the right to make technical improvements!

3
Table of contents
1 Scope of supply 4
2 Order numbers 4
3 Basic safety instructions 5
4 Introduction 6
5 Installing the OTT SV 100 9
5.1 riteria for selecting a suitable installation location 9
5.2 Information on supply voltage 11
5.3 ompatible cable types 11
5.4 Installing the OTT SVR 100 12
5.5 onnecting the OTT SVR 100 to the data logger 16
5.6 Information on using the RS-485 interface 16
6 SDI-12-commands and responses 17
6.1 Overview of standard SDI-12 commands 17
6.2 Standard commands 18
6.2 Advanced SDI-12 commands 20
7 Performing maintenance work 22
8 epairs 22
9 Information on disposal of old devices 23
10 Troubleshooting 24
11 Technical Data 25
Appendix A – Connecting the OTT SV 100 to OTT netDL
via the S-485 interface 26
Appendix B – Wall bracket dimensions/mounting hole positions 28
Appendix C – Note on the declaration of conformity 29
Appendix D – S-485 interface with Modbus protocol ( TU) 30
Appendix E – OTT SV 100 Operating Program 32

1 Scope of supply
䊳
OTT SV 100 – Radar sensor for contactless measurement of the surface velocity of a flowing
waterway; with RS-232- and RS-485-interface (SDI-12- or Modbus protocol)
– Installation accessory kit (two-piece swivel mount, consisting of device and wall
brackets, and four M8 hexagon bolts)
– onnecting cable, 10 m; with 12-pin angled connector
– Quick guide
– Acceptance test certificate (FAT)
2 Order numbers
䊳
OTT SV 100 OTT SV 100 radar sensor
– RS-485 interface with SDI-12 protocol (preset) 63.151.001.9.0
– RS-485 interface with Modbus protocol (preset) 63.151.002.9.0
䊳 Accessories OTT USB/SDI-12 interface 65.050.001.9.2
– for temporary connection of OTT sensors to a P
using an SDI-12 or RS-485-interface
– including USB connecting lead; USB A
to USB B connector; 3 m
S-232 connecting lead 97.120.371.4.2
– 1.5 metres, 9-pin Sub-D socket/
open cable end (5 wires)
S-232/USB interface adapter 97.961.168.9.5
OTT SV 100 Operating Program
– P Software for
· Setting the OTT SVR 100 operating parameters
(protocol on RS-485 interface)
· Updating the OTT SVR 100 firmware
· ontinuous measurement and representation of graphs
– User interface language: English
– Download setup file from "www.ott.com/resources"
Operating instructions
Format DIN A4, 32 pages; supplementary information
to quick guide (included in scope of supply)
– German 63.151.001.B.D
– English 63.151.001.B.E
– French 63.151.001.B.F
– Spanish 63.151.001.B.S
4

3 Basic safety instructions
䊳 Before commissioning the OTT SVR 100, read these operating instructions and
the quick guide enclosed with the device. Ensure you are very familiar with
how to install and operate the OTT SVR 100. Retain these operating instruc-
tions for subsequent reference
䊳 The OTT SVR 100 is used for contactless measurement of the surface velocity of a
flowing waterway. Only use the OTT SVR 100 as described in these operating
instructions. For further information ➝ see hapter 4, Introduct on.
䊳 Observe all detailed safety instructions provided for the individual work steps.
All safety instructions provided here are indicated by a warning symbol placed
next to them.
䊳 Never use the OTT SVR 100 in potentially explosive areas.
For further information ➝ see hapter 5, Install ng the OTT SVR 100
䊳 Note that the OTT SVR 100 may only be installed by specialist personnel
(e.g. qualified electrician).
For further information ➝ see hapter 5, Install ng the OTT SVR 100
䊳 Make sure that the electrical, mechanical and climatic specifications set out in
the technical data are complied with!
For further information ➝ see hapter 11, Techn cal Data.
䊳 Do not make any changes or modifications to the OTT SVR 100. hanges or
modifications void all warranty entitlements. In addition, the radio approval
necessary for operation is invalidated!
䊳 Only have a defective OTT SVR 100 inspected and repaired by our repair
centre. Never repair it yourself!
For further information ➝ see hapter 8, Repa r.
䊳 After decommissioning, dispose of the OTT SVR 100 properly. Never dispose
of the OTT SVR 100 with normal household waste.
For further information ➝ see hapter 10, Instruct ons for d sposal of used
dev ces.
Federal Communications Commission (FCC) Approval
This equipment has been tested and found to comply with the limits for a class B
digital device, pursuant to part 15 of the F Rules. These limits are designed to
provide reasonable protection against harmful interference in a residential instal-
lation. This equipment generates, uses and can radiate radio frequency energy
and if not installed and used in accordance with the instructions, may cause harm-
ful interference to radio communications. However, there is no guarantee that
interference will not occur in a particular installation. If this equipment does cause
harmful interference to radio or television reception, which can be determined by
turning the equipment off and on, the user is encouraged to try to correct the
interference by one or more of the following measures:
䊳 Reorient or relocate the receiving antenna
䊳 Increase the separation between the equipment and receiver
䊳 onnect the equipment into an outlet on a circuit different from that to which
the receiver is connected
䊳 onsult the dealer or an experienced radio/TV technician for help
This equipment has been verified to comply with the limits for a class B computing
device, pursuant to F Rules. In order to maintain compliance with F regu -
lations, shielded cables must be used with this equipment. Operation with non -
approved equipment or unshielded cables is likely to result in interference to radio
and TV reception. The user is cautioned that changes and modifications made to
the equipment without the approval of manufacturer could void the user’s authority
to operate this equipment.
5

4 Introduction
The OTT SVR 100 radar sensor is used for continuous contactless measurement of
the surface velocity of a flowing waterway (= index velocity).
A connected data logger can use this index velocity (preferably measured in the
area of the maximum velocity) to calculate the flow using the "velocity index
method". The water level that is also required for this calculation can be deter-
mined using any water level sensor (e.g. pressure probe or OTT RLS radar level
sensor). To obtain accurate flow values, the entire measuring system must be cali-
brated during commissioning, e.g. using the "OTT Prodis 2" software.
The functional principle of the OTT SVR 100 is based on the physical Doppler
effect. A transmission aerial emits radar pulses with a typical frequency of 25.3
GHz at a nominal angle of 30 degrees to the horizontal. The alignment must be
parallel, and ideally against the main flow direction of the waterway. If the water
surface is moving and has a minimum roughness, the radar pulses are reflected
with a slight frequency shift and are received by a reception aerial on the
OTT SVR 100. From the frequency shift, the radar sensor uses a trigonometric
function to calculate the average flow velocity within the radar footprint projected
onto the water surface. The exact tilt angle necessary for the calculation is pro -
vided by an integrated tilt sensor.
In addition, a vibration sensor transmits a specific vibration index for every mea-
sured velocity value. This index indicates whether measured values have potential-
ly been impaired by vibration of the device. For example, vibrations can be
caused by traffic on bridges or the influence of wind on the cantilever arms.
A physical RS-485 interface is available to connect the OTT SVR 100 to a data
logger or peripherals, and communication with the radar sensor is via the SDI-12
or Modbus transmission protocol 1). In addition, the OTT SVR 100 has an RS-232
interface for service purposes (e.g. firmware updates).
The radar sensor can be configured using SDI-12 transparent mode on a data
logger or via the OTT USB/SDI-12 interface (accessory), or alternatively via the
RS-232 interface using special service software.
1) set using the "OTT SVR 100 Operating Program"; see Appendix E
Fig. 1: Schematic representation of the
velocity index method.
Q : Flow [m3/s]
A : ross-sectional area [m2]
k : orrection factor [1]
Q = vm· A = vi· k · A
vm: Average flow velocity [m/s]
vI: Index velocity at the surface [m/s]
6

The transmission aerial has a horizontal opening angle of 12° and the vertical
opening angle is 24°. The resulting sensor radar footprint can be found in the
example applications in Figures 3 and 4 and the table in hapter 5.1.
A swivel mount allows easy, problem-free installation, even on unsuitable sur-
faces. The electrical connection is via a factory-assembled 12-pin angled con -
nector and a mounting socket.
The cable length between the radar sensor and the data logger can be up to
1000 metres (depending on the wire cross-section used).
The entire radar sensor – provided it is installed as described in these oper -
ating instructions – has a flood-proof design.
Transmission and
reception aerial cover
(Radom)
Swivel mount
Connecting cable
Fig. 2: OTT SVR radar sensor overview.
OTT SVR 100
Pressure probe
Fig. 3: Example application 1: OTT SVR
100 installed on a bridge.
The projection of the radar footprint on the
water surface is elliptical.
In the example shown, the water level is
determined using a pressure probe.
7

OTT RLS OTT SVR 100
Fig. 4: Example application 2:
OTT SVR 100 installed on an auxiliary
structure, e.g. a cantilever arm.
The projection of the OTT SVR 100 radar
footprint on the water surface is elliptical.
In the example shown here, the water level
is determined using a contactless OTT RLS
radar sensor.
8

5 Installing the OTT SV 100
WA NING isk of explosion due to spark formation and electrostatic charge
If the OTT SVR 100 is operated in an explosive atmosphere, there is a risk of the
atmosphere igniting. This can cause an explosion involving a risk of very severe
injury and damage.
䊳 Never operate the OTT SVR 100 in potentially explosive areas (e.g. waste
water channels). The OTT SVR 100 does not have EX protect on
(explosion protection)!
Please note:
䊳 The electrical installation of the OTT SVR 100 may only be carried out by
specialist personnel (e.g. qualified electrician)!
5.1 Criteria for selecting a suitable installation location
䊳 Possible installation locations include bridge structures, pontoons or auxiliary
constructions that are located directly above the section of waterway to be
measured.
䊳 The minimum distance between the lower edge of the sensor and the water
surface must be 0.5 m (dead zone within which no usable measurement can be
obtained).
䊳 Select an installation point that is sufficiently high to allow measurement even at
high water.
䊳 The installation point must be stable and free of vibration; vibrations and move-
ment of the installation point are to be avoided (traffic on bridge structures or
influence of wind on cantilever arms impair the measured result). Bridges are
subject to movements of up to several centimetres due to changes of load and
temperature fluctuations. Installation on or in the immediate vicinity of bridge
piers is not recommended. Bridge piers influence the flow velocity and normally
cause back-water zones and turbulence.
䊳 Around the sensor radar footprint, the water surface should have a minimum
roughness of 1 mm. Avoid macro turbulences, locations with foam, swells and
sections of waterway where obstructions or bridge piers cause changes in the
water level.
䊳 Wind influence on the water surface impairs the measured result.
䊳 Select an installation location that does not dry out at low water.
䊳 The sensor radar footprint (see Figures 3 and 4) must be completely free of
obstructions.
䊳 There may not be any inflows, outlets, weirs, ground sills or other obstructions
in front of the measuring point; optimum minimum distance: 10 x waterway
width at measuring point!
䊳 As far as possible, the flow direction should be straight, parallel to the bank
and free of irregular speed distributions.
– Rule of thumb: the flow direction is considered parallel to the bank if the-
water runs straight over a length of 5 … 10 x W*.
– Recommended: straight waterway for 2 x W* upstream of the measuring
point and 1 x W* downstream of the measuring point.
* W = width of watercourse at the measuring point
䊳 The bottom of the waterway and the measuring point cross-section must be as
stable as possible. Large stones in the measuring cross-section should be avoid-
ed, as should vegetation in the waterway. Vegetation on the bank can lead to
incorrect measurements, particularly if it is close to the sensor radar footprint.
9

䊳 An optimum measuring point has a uniformly shaped cross-section with an
even velocity distribution and a stable position of the maximum surface velocity.
䊳 Avoid large metallic surfaces close to the sensor radar footprint (reflections
from these surfaces can falsify the measured result).
䊳 Table for determining the approximate size of the sensor radar footprint:
Height "h" Distance "a" Tilt angle 30° Distance"a" Tilt angle 45°
[m] [m] l x w [m] [m] l x w [m]
1.0 1.7 2.0 x 0.4 1.0 0.9 x 0.3
2.0 3.5 3.9 x 0.8 2.0 1.8 x 0.6
3.0 5.2 5.9 x 1.3 3.0 2.7 x 0.9
4.0 6.9 7.9 x 1.7 4.0 3.6 x 1.2
5.0 8.7 9.8 x 2.1 5.0 4.5 x 1.5
7.5 13.0 14.8 x 3.2 7.5 6.7 x 2.2
10.0 17.3 19.7 x 4.2 10.0 8.9 x 3.0
12.5 21.7 24.6 x 5.3 12.5 11.1 x 3.7
15.0 26.0 29.5 x 6.3 15.0 13.4 x 4.5
17.5 30.3 34.4 x 7.4 17.5 15.6 x 5.2
20.0 34.6 39.3 x 8.4 20.0 17.8 x 5.9
22.5 39.0 44.3 x 9.5 22.5 20.0 x 6.7
25.0 43.3 49.2 x 10.5 25.0 22.3 x 7.4
For definitions of height "h" distance "a", "l" and "w", see Figures 6 and 7.
The specified figures are minimum dimensions. Where possible, select a signi -
ficantly larger obstruction-free area.
✓✗
✗
l
w
Fig. 6: Optimum alignment of sensor radar
footprint with waterway flow direction and
dimensions of radar footprint.
10

䊳 Wave height measurement using the OTT SVR 100 is not possible.
䊳 The OTT SVR 100 and OTT RLS can be combined at a single measuring point
with no problems as they do not influence one another. Likewise, multiple
OTT SVR 100s can be used in parallel on very wide flowing waterways.
5.2 Information on supply voltage
The OTT SVR 100 requires a supply voltage of 9 … 28 V D , typically 12/24 VD
(e.g. form battery or mains connection with electrically isolated safety extra low
voltage).
The OTT SVR 100 is ready to use as soon as the supply voltage is connected. The
first valid measured values are available around 30 seconds later.
Please note:
䊳 When using solar panels, we recommend using a surge protector.
5.3 Compatible cable types
The connecting cable with angled connector supplied (length: 10 metres) can be
extended to a maximum of 1000 m. Recommended cable type: Twisted pair
cable, unscreened design. However, the wires intended for the supply voltage do
not have to be a twisted pair.
The maximum cable length depends on the wire corss-section used:
onnecting cable for typical. 12 VD for typical. 24 VD
– 2 x 2 x 0.50 mm2 ≤ 150 metres ≤ 250 metres
– 2 x 2 x 0.75 mm2 ≤ 250 metres ≤ 1000 metres
Hight „h”: 0.5 … 25 m (17 m*)
max.50m
* a= 20°
Distance „a“ (centre of sensor radar footprint)
Fig. 7: Maximum distances of
OTT SVR 100 to water surface.
11

5.4 Installing the OTT SV 100
Attaching the swivel mount (see also Appendix )
䊳 Surface: oncrete or brickwork
䊳 Attachment material: e.g. hexagonal wood screws M6 x 40 + plastic dowels
䡵 Make two holes (Ø 8 mm) using a hammer drill
(use the wall bracket for marking the holes).
䡵 Insert the plastic dowels into the drill holes.
䡵 Attach the wall bracket with hexagonal wood screws.
䡵 Mount the housing bracket (without sensor) in the wall bracket and slightly
tighten the hexagon bolts A(see Fig.10).
䊳 Surface: any steel construction, e.g. cantilever arm
䊳 Attachment material: e.g. hexagon bolt M12 x 25 + hexagon nut M12 +
washers
䡵 Make a hole (Ø 13 mm) in the steel construction.
䡵 Attach the wall bracket using a hexagon bolt, washers and hexagon nut.
䡵 Mount the housing bracket (without sensor) in the wall bracket and slightly
tighten the hexagon bolts A(see Fig.10).
Plastic dowel
Wall bracket
Wall bracket
Steel construction
Washer
Hexagon bolt
Hexagon nut
Hexagon
wood screw
Fig. 8: Attaching the swivel
mount (wall bracket).
Both attachment types are intended as
examples and are possible for either
wall or ceiling installation.
12

Connecting the cable with angled connector
Please note: No moisture may get into the angled connector/the mounting
socket. Protect the OTT SVR 100 from precipitation during installation. Ingress of
moisture can lead to malfunctions and corrosion.
䡵 Align the angled connector in the correct position (observe keying nose) and fit
on the mounting socket.
䡵 Where possible, tighten the union nut by hand if using a fork wrench. Tighten-
ing torque max. 2 Nm. The union nut engages when tightened.
䡵 Run the connecting cable upwards in a loop and secure on the housing bracket
with a cable tie (strain relief).
Attaching the radar sensor
䡵 Mount the sensor in the housing bracket and slightly tighten the hexagon bolts
B (see Fig. 10).
䡵 Adjust the sensor tilt angle to the horizontal:
– Recommended: 30°
– Minimum/maximum: 20°/60°
䡵 arefully tighten the hexagon bolts B (housing shell) (see Figure. 10).
䡵 Align the sensor axis with the flow direction (see Figure 6).
䡵 arefully tighten the hexagon bolts A (wall/housing bracket) (see Figure 10).
䡵 heck the alignment of the OTT SVR 100 again!
Cable tie
Angled connector
Mounting socket
Connecting cable
Fig. 9: onnecting the angled connector of
the connecting cable on the OTT SVR 100.
13

Hexagon bolt A
Hexagon bolt B
Wall bracket
Housing bracket
Fig. 10: OTT SVR 100 – Installation
of swivel mount.
14

20° ≤ a≤ 60°
Recommended: a= 30°
60°
20°
a
30°
0°
20°
45°
30°
60°
Fig. 11: Adjusting the sensor tilt angle (␣)
on the OTT SVR 100.
15

5.5 Connecting the OTT SV 100 to the data logger
䡵 onnect the OTT SVR 100 to an SDI-12 input on the data logger. Refer to the
data logger manual for more details. Refer to Figure 12 for the OTT SVR 100
terminal assignment. The maximum cable length is 1000 m. Recommended
wire cross-section: see hapter 5.3.
The SDI-12 commands that can be used with the OTT SVR 100 can be found in
hapter 6, SDI-12-commands and responses.
5.6 Information on using the S-485 interface
The RS-485 interface with SDI-12 protocol is designed and tested for use with OTT
and Sutron data loggers. For details of connecting the OTT SVR 100 to OTT netDL
via the RS-485 interface ➝ see Appendix A.
OTT is unable to guarantee proper functioning if you connect the OTT SVR 100 to
a data logger from a third-party manufacturer via the RS-485 interface with
SDI-12 protocol!
Fig. 12: Wire assignment
in connecting cable (12-wire).
The RS-232 interface is provided
for service purposes.
The unused wires (pink, blue, red, black,
purple) must be isolated from one another.
Otherwise, there is a risk of malfunctions.
Connecting cable
white GND
brown +9 … +27 VDC
grey SignalGND
green RS-232TxD
yellow RS-232 RxD
violet RS-485 D+ (B)
orange RS-485 D– (A)
not used
16

6 SDI-12-commands and responses
The OTT SVR 100 communicates using the physical RS-485 interface via the SDI-12 transfer protocol. In this technical
documentation, you will find a detailed description of the SDI-12 commands implemented in the SDI-12 transfer protocol.
Further information on the SDI-12 standard can be found in the document "SDI-12; A Serial-Digital Interface Standard for
Microprocessor-Based Sensors; Version 1.3" (see website "www.sdi-12.org").
All advanced, manufacturer-specific SDI-12 commands on the OTT SVR 100 begin with "O" for OTT. With these commands
it is possible to configure the OTT SVR 100, for example using the "SDI-12 transparent mode" on a data logger or with the
OTT USB/SDI-12 interface (accessory).
Conventions for measured value formats
p– Sign (+,–)
b– Figure (before the decimal point)
e– Figure (after the decimal point)
!– Ends a command
6.1 Overview of standard SDI-12 commands
䊳 a! Acknowledgement active
䊳 aI! Send identification
䊳 aAb! hange sensor address
䊳 ?! Query sensor address; factory setting: 0
䊳 aM! Start measurement
䊳 aD0! Send data
䊳 aR0! ontinuous measurement
䊳 aMC! Start measurement and request R ( yclic Redundancy heck)
䊳 aC! Start concurrent measurement (simultaneous measurement with multiple sensors on one bus line)
䊳 aCC! Start concurrent measurement and request R
䊳 aV! Start system test
Advanced commands (manufacturer specific)
䊳 aOAA<value>! Set internal filter type
aOAA! Read internal filter type
Factory setting: 1➝Floating mean
䊳 aOAB<value>! Set measuring sensitivity
aOAB! Read measuring sensitivity
Factory setting: 14
䊳 aOAC<value>! Set filter length
aOAC! Read filter length
Factory setting: 1➝internal filter deactivated
䊳 aOSD<value>! Set flow direction filter
aOSD Read flow direction filter
Factory setting: 0➝Flow direction filter deactivated; both flow directions are recorded
䊳 aOSU<value>! Set unit for "flow velocity" measured values
aOSU Read unit for "flow velocity" measured values
Factory setting: 0➝m/s
17

6.2 Standard commands
Command esponse Description
a! a<CR><LF> Acknowledgement active
a– Sensor address; factory setting = 0
aI! allccccccccmmmmmm…
…vvvxxxxxx<CR><LF>
Send identification
a – Sensor address
ll – SDI-12-protocol version
cccccccc – Manufacturer identification (company name)
mmmmmm – Sensor designation
vvv – Sensor version (here firmware version)
xxxxxx – Additional designation (here serial number)
OTT SVR 100 response = 013OTT SVR100485xxxxxx
aAb! b<CR><LF> hange sensor address
a– Old sensor address
b– New sensor address
?!a<CR><LF> Query sensor address
a– Sensor address
aM! atttn<CR><LF> Start measurement
a – Sensor address
ttt – Time in seconds until sensor has determined
measured result
OTT SVR 100 response = 000 seconds
n – Number of measured values
OTT SVR 100 response = 6
aD0! a<value1><value2><value3> …
… <value4><value5><value6> …
… <CR><LF>
Send data (after aM!)
a – Sensor address
<value1> – Average flow velocity
(floating mean over approx. 30 seconds)
Measured value format:
+b.eeee … pbb.eee [m/s] 1)
+b.bbbb … pbbbb.e [cm/s] 1)
+b.bbbb … pbb.eee [ft/s] 1)
<value2> – urrent flow velocity:
Measured value format:
+b.eeee … pbb.eee [m/s] 1)
+b.bbbb … pbbbb.e [cm/s] 1)
+b.bbbb … pbb.eee [ft/s] 1)
<value3> – Sensor tilt angle to horizontal
Meausred value format: +bbb [°]
<value4> – Flow direction
Format: pb [1]
–1 = Away from sensor
+1 = Toward sensor
If the flow direction filter is deactivated
(aOSD0!) this value shows the relevant flow
direction for the measured flow velocity; if the
filter is activated the value is fixed at the corre-
sponding filter setting
(e.g. aOSD2! ➝–1).
<value5> – Signal quality index
Format: +00b [1]
+000 = Excellent signal quality
+001 = Good signal quality
+002 = Poor signal quality
➝ impaired measured values
+003 = Very poor signal quality;
➝ unacceptable measured values
1) depending on the set unit (advanced command aOSU<value>!)
18

Command esponse Description
<value6> – Vibration index
Format: +00b [1]
+000 = No device vibration
+001 = Slight device vibration
+002 = Significant device vibration
➝ impaired measured values
+003 = Very significant device vibration;
➝ unacceptable measured values
aR0! a<value1><value2><value3> …
… <value4><value5><value6> …
… <CR><LF>
The OTT SVR 100 continuously measures the flow velocity
This command enables measured results to be obtained even
without the aM!/aD0! command combination; for details
see aD0! command.
aMC! atttn<CR><LF> Start measurement and request R ( yclic Redundancy
heck); for details see aM!command.
The response to the subsequent aD0! command is extended
with a R value: a<value1><value2><value3> …
… <value4><value5><value6><CRC><CR><LF>
aC! atttnn<CR><LF> Start measurement and request R ( yclic Redundancy
heck); for details see aM!command. The number of mea-
sured values in the response to this command has two digits:
nn = 06.
aCC! atttnn<CR><LF> Start concurrent measurement (simultaneous measurement
with multiple sensors on one bus line) and request R
( yclic Redundancy heck); for details see aM!. The number
of measured values in the response to this command has two
digits: nn = 06.
The response to the subsequent aD0! command is extended
with a R value: a<value1><value2><value3> …
… <value4><value5><value6><CRC><CR><LF>
aV! atttn<CR><LF> Perform system test
a – Sensor address
ttt – Time in seconds until the sensor provides the
result of the system test
OTT SVR 100 response = 000
n – Number of measured values
OTT SVR 100 response = 2
aD0! a<value1><value2><CR><LF> Send data (after aV!)
a – Sensor address
<va1ue1> – Result of system test: Firmware
+0 = Internal error occured
+1 = Firmware working properly
<value2> – Result of system test: Internal sensors …
+0 = are (partially) inactive
+1 = are all active
19

6.2 Advanced SDI-12 commands
Command esponse Description
䊳 Set/read internal filter type
aOAA<value>!
aOAA!
a<value><CR><LF>
a<value><CR><LF>Calculat on
Set internal filter type
Read internal filter type
a – Sensor address
<value> – 0 = IIR filter (Infinite Impulse Response filter)
1 = Floating mean
Factory setting: 1
The OTT SVR 100 determines approx. 20 individual mea-
sured values for the flow velocity per second. Depending on
factors such as the roughness of the water surface, wind
influence, precipitation or turbulence, the individual mea-
sured values can be very scattered. The internal filter allows
them to be "smoothed". In principle, both filter types lead to
very similar results, but the IIR filter responds faster if there
are significant changes in flow velocity. When using the
floating mean, you can specify the number of individual
measured values (aOAC<value>!command). This filter
works totally independently of the "average flow velocity"
(value 1 in the response to the aD0!command)
IIR filter calculation:
vfiltered (t) = vcurrent (t) *Q + vfiltered (t – 1) *(1 – Q) Q = 1/3
䊳 Set/read measuring sensitivity
aOAB<value>!
aOAB!
a<value><CR><LF>
a<value><CR><LF>
Set measuring sensitivity
Read measuring sensitivity
a – Sensor address
<value> – bb
Input/output without leading zeroes
Value range: 10 … 40
Factory setting: 14
You can use this command to set the sensitivity of the radar
sensor. The advantage of a high sensitivity (low value) is that
measurements can be taken on very smooth water surfaces.
On the other hand, there is a risk that unwanted effects will
also be recorded, for example movement of vegetation on
the bank.
For normal applications, you should not change the factory
setting.
䊳 Set/read internal filter length (filter type: floating mean)
aOAC<value>!
aOAC!
a<value><CR><LF>
a<value><CR><LF>
Set filter length
Read filter length
a – Sensor address
<value> – bbb
Input/output without leading zeroes
Value range: 1; 16 … 256
Factory setting: 50
You can use this command to specify the number of individ-
ual measured values from which the internal filter calculates
a floating mean (prerequisite: aOAA1!).
The setting "1" deactivates the internal filter.
20