OTT CBS User manual

English
Operating instructions
Bubble Sensor OTT CBS
valid for instruments with firmware versions from 1.20.0!

We reserve the right to make technical changes and improvements without notice.

3
Table of Contents
1 Scope of supply 4
2 Order numbers 4
3 Introduction 5
4 Installing OTT CBS 7
4.1 Preparing the OTT CBS for installation 7
4.2 Fastening OTT CBS 7
4.3 Connecting measuring tube to OTT CBS 8
5 Installing bubble chamber 9
5.1 Installing bubble chamber for surface water 9
5.2 Installing bubble chamber for ground water 10
6 Connecting OTT CBS 12
6.1 Connect power supply 13
6.2 Connecting the OTT CBS to any data logger using the S I-12 interface 13
6.3 Connecting the OTT CBS to any data logger using the RS-485 interface (S I-12 / Modbus protocol) 13
6.4 Connecting the OTT CBS to any data logger using the 4 … 20 mA interface 13
6.5 etermining the maximum load resistance at the 4 … 20 mA interface 14
7 Activating the purge function 15
8 Adjusting operating parameters using the service interface 16
8.1 Setting the serial interface type 16
8.2 Setting measurement type of the 4 … 20 mA interface to level or depth measurement 17
8.3 Scaling the measuring range for the 4 … 20 mA interface 17
8.4 Setting the measuring system for the 4 … 20 mA interface 18
8.5 Setting measurement type of the 4 … 20 mA interface to water level or pressure measurement 18
8.6 Factory setting of the operating parameters 18
9 SDI-12 commands and responses 19
9.1 Overview of S I-12 commands 19
9.2 Standard commands 21
9.3 Meta data commands 23
9.4 Advanced S I-12 commands 24
10 Carrying out maintenance work 29
10.1 Activating purge function 29
10.2 Cleaning bubble chamber 29
10.3 Testing the measuring tube 29
11 "Status" LED 30
12 ote about the disposal of old devices 30
13 Technical Data 31
Appendix A – Connecting the OTT CBS to OTT netDL or
OTT DuoSens using the SDI-12/RS-485 interface 32
Appendix B – Connecting the OTT CBS to an OTT netDL or
OTT DuoSens using the 4 … 20 mA interface 35
Appendix C – RS-485 interface with Modbus protocol (RTU) 37
Appendix D – ote on the declaration of conformity 39

1 Scope of supply
䊳 OTT CBS –1 Bubble Sensor OTT CBS with possibility for connecting measuring tubes with
4 mm/2 mm external/internal diameter
–1 Installation kit (top hat rail with fastening parts; screw terminal blocks,
pin jumpers)
–1 Operating Instructions
–1 Factory acceptance test (FAT) certificate
2 Order numbers
䊳 OTT CBS Bubble Sensor OTT CBS 63.200.001.9.2
䊳Accessories Measuring tube
4 mm/2 mm external/internal diameter; transparent PE
– 50 m 99.420.050.9.5
– 100 m 99.420.100.9.5
Combined measuring tube/
bubble chamber suspension cable
black, with kevlar core for length stabilization, measuring tube
with 4 mm/2 mm external/internal diameter; transparent PE
– 50 m 99.420.009.9.5
– 100 m 99.420.008.9.5
Measuring tube
6 mm/4 mm with sheathing
Length as requested 20.500.133.5.5
Measuring tube
6 mm/4 mm without sheathing
Length as requested 20.500.302.5.5
Bubble chamber suspension cable
black, with Kevlar core for length stabilization
– 50 m 99.000.050.9.5
– 100 m 99.000.100.9.5
Bubble chamber for ground water
– for observation wells beginning at 2" diameter, 670 gram 55.510.051.4.2
Bubble Pot EPS 50 for surface water
– hose connector 4 mm/2 mm 55.510.048.3.2
– hose connector 6 mm/4 mm 55.510.049.3.2
Straight pipe fitting
– for connecting measuring tubes with 63.200.025.9.2
1/8" internal diameter and 3/8" external diameter
4

3 Introduction
The OTT CBS, working on the air bubble principle, can be used for measuring
ground water or water levels depending on the bubble chamber used.
To meet the various demands of the station, three different versions of the
OTT CBS bubble sensor are available:
"Standard" version:
䊳Measuring range 0 … 15 m or 0 … 1500 mbar
䊳Resolution 1 mm or 0.1 mbar
䊳Accuracy ±5 mm
"USGS specification" version:
䊳Measuring range 0 … 15 m or 0 … 1500 mbar
䊳Resolution 1 mm or 0.1 mbar
䊳Accuracy measuring range 0 … 15 ft: ±0.01 ft
measuring range 15 … 50 ft: ±0.065 % of measured
value or ±0.02 ft, whichever is less
"30 m measuring range" version:
䊳Measuring range 0 … 30 m or 0 … 3000 mbar
䊳Resolution 1 mm or 0.1 mbar
䊳Accuracy ±5 mm
The compressed air produced by a piston pump flows via a measuring tube and
the bubble chamber into the water to be measured. The pressure created in the
measuring tube is directly proportional to the water column above the bubble
chamber. The OTT CBS determines the barometric air and bubble pressure one
after the other. By taking the difference between the two signals, the OTT CBS
calculates the height of the water level above the bubble chamber.
The power supply can be provided from a mains adapter, battery or solar power.
The OTT CBS contains a purge function. This clears the measuring tube and the
bubble chamber of any minor contamination by pumping a large volume of air
into the measuring tube.
By using an intelligent pump strategy, no air drying unit is necessary for the
measuring range of 0 … 15 m.
Fig. 1: Overview of OTT CBS.
Hose connection
for measuring tube
Air filter for
incoming air
DIP switch compartment
Status LED
Button for activating
the purge unit
Terminal blocks A and B
for connecting the datalogger
and power supply
5

For the display of any error states that may occur, the OTT CBS has a "Status“
LE (see Fig. 1).
Connection to a data logger can be established via a choice of
䊳 S I-12,
䊳 RS-485 (2-wire; S I-12-/Modbus protocol) or
䊳 4 … 20 mA (current loop)
interface.
An additional service interface with eight-position IP switch can be used to adjust
various operating parameters.
Bubble pot
EPS 50
Groundwater
bubble chamber
Measuring tube
Fig. 2: The main layout of a level
station with OTT CBS bubble sensor.
6

4 Installing OTT CBS
4.1 Preparing the OTT CBS for installation
䡵 If required and not yet completed: Adjust operating parameters using service
interface (see chapter 8).
4.2 Fastening OTT CBS
The OTT CBS is designed only to be installed on top hat rails (a section of top hat
rail is supplied with the OTT CBS). Choose a dry and dust free location for the
installation such as a gage station or control cabinet.
䡵 First attach the OTT CBS on the upper edge of the top hat rail and then press
the underside against the top hat rail until it clicks into place.
Demounting OTT CBS
䡵 First press one locking device downwards and pull the OTT CBS slightly for-
wards at this point. Press the second locking device downwards and remove
the OTT CBS upwards from the top hat rail.
Top hat rails Locking device
Fig. 3: Fastening the CBS on the top
hat rail (left)/demounting (right).
7

4.3 Connecting measuring tube to OTT CBS
To install the measuring tube on the OTT CBS, proceed as follows:
Measuring tube with 2 mm internal diameter
䡵 Cut off the end of the measuring tube square with a sharp knife and push onto
the factory fitted connection nipple.
Maximum length of the measuring tube: 100 m.
Measuring tube with 4 mm internal diameter
䡵 Cut off the end of the measuring tube square with a sharp knife.
䡵 Remove cap nut (width across flats: 10) and pull off the (short) factory mounted
measuring tube from the connection nozzle.
䡵 Push cap nut over the measuring tube (Ø 4 mm).
䡵 Push measuring tube onto the connection nozzle.
䡵 Push the cap nut back onto the connection nozzle and tighten by hand.
Maximum length of the measuring tube: 75 m.
Measuring tube with 1/8" internal diameter
A special pipe fitting for the 1/8" internal diameter measuring tube is available
(accessory). Please follow the instructions delivered with the pipe fitting for
installing the pipe.
Maximum length of the measuring tube: 100 m.
Fig. 4: Connecting measuring
tube on OTT CBS.
Cap nut
(wrench size: 10)
Connection
nozzle
Measuring tube
Ø: 4 mm
1.
2.
Connection nipple
Measuring tube
Ø: 2 mm
8

5 Installing bubble chamber
Please ensure the following points are noted during installation:
䊳 No contamination or moisture may be allowed into the measuring tube.
䊳When immersing the bubble chamber (only EPS 50), the OTT CBS must be
activated, so that the piston pump is operating during this process.
䊳o not damage or kink the measuring tube during installation.
䊳Lay the measuring tube such that there is a continuous drop from the OTT CBS
towards the bubble chamber. Otherwise moisture could collect in a "hollow"
and potentially block the tube with the formation of drops (see Fig. 5)
5.1 Installing bubble chamber for surface water
We recommend using the Bubble Pot EPS 50 for measurements in surface waters.
See "Bubble Pot EPS 50" installation instructions for information on its installation.
Fig. 5: Routing requirements
for measuring tube.
1" metal tube
Direction of flow
Bubble pot
EPS 50
Measuring tube
9

5.2 Installing bubble chamber for ground water
To install the bubble chamber for ground water, proceed as follows:
䡵 etermine depth of the bubble chamber (e.g. using a contact gauge). The
bubble chamber must be positioned under the lowest expected water level.
Depth = distance from bubble opening to upper edge of the
top cap
䡵 Push the measuring tube into the cable gland of the bubble chamber as far as
it goes.
䡵 Tighten the cable gland firmly by hand
䡵 Cut suspension cable to length; suspension cable length = depth +
125 cm (to protect the suspension cable from being twisted off, it can be
melted, with a cigarette lighter for example).
䡵 Feed the suspension cable through the hole in the bubble chamber as shown in
figure 6 and tie firmly.
䡵 Slide cover into position B (upwards), see Fig. 6.
Fig. 6: Installing bubble
chamber for ground water.
When lowering the bubble chamber, the
cover must be in position B! The cover
prevents water entering the measuring
tube during installation.
uring initial startup, over pressure builds
up in the measuring tube. As a result, the
cover falls back to position A and opens the
measuring tube in the process.
Measuring pipe
Suspension cable
bubble chamber
Metal pin
Cover in
position A
Bubble opening Cover in
position B
Cable
gland
Hole
Bubble pot
10

䡵 As shown in Fig. 7, attach the suspension cable of the bubble chamber to the
retainer on an OTT top cap already mounted. The retaining plate allows a fine
height adjustment afterwards.
䡵 Secure the suspension cable against slipping with a knot.
䡵 If top caps without retainers are used, ensure the suspension cable is attached
securely.
䡵 Check all knots and attachments for correct position and firmness.
䡵 Lower the bubble chamber slowly into the observation well with the suspension
cable.
䡵 Feed the measuring tube out of the observation well through a hole.
Fig. 7: Installing bubble chamber for
ground water – attaching suspension cable.
Top cap
Retainer
Observation
well
Suspension cable
bubble chamber
Securing knot
Retaining plate
Measuring tube
11

6 Connecting OTT CBS
The OTT CBS has the following interfaces
䊳S I-12
䊳RS-485, (2-wire; S I-12 /Modbus protocol)
䊳4 … 20 mA (current loop)
as well as a
䊳connection for the power supply (UBat + GN ).
The three interfaces make it possible to connect the OTT CBS both to OTT data
loggers and to any data logger by another manufacturer that has the correct
interfaces. Note that only one of the interfaces at a time can be used (no parallel
operation of interfaces).
The S I-12 interface meets S I-12 Standard 1.4.
All electrical connections are made using two screw terminal strips (supplied) at
terminal blocks A and B on the underside of the OTT CBS.
Fig. 8: Assignments for the screw terminal
strips A and B of the OTT CBS.
431 2 431 2
+UBat
4 … 20 mA +
4 … 20 mA –
GND
RS-485 A/D+ *
RS-485 B/D– *
SDI-12 DATA
SDI-12 GND
A B
Screw terminal strip
* RS-485 interface with
SDI-12/Modbus protocol
12

6.1 Connect power supply
The OTT CBS requires a power supply of 10 … 30 V C, typ. 12/24 V C (e.g.
using batteries or mains connection with galvanically separated low safety voltage).
Please note the following points when dimensioning the power supply:
䊳Maximum power consumption per day: 3700 mAh (typ. 320 mAh/day) (with
1 min measurement interval and 100 m measuring tube using the 4 … 20 mA
interface)
䊳Peak current consumption: temporary max. 2 A
䊳Protect the supply voltage with a microfuse (e.g. 2.5 A, slow-blow)!
䊳When using solar panels, we recommend the use of an overvoltage protection
device.
To supply the OTT CBS with power, proceed as follows:
䡵 Connect the power supply to screw terminal strip A of the OTT CBS as shown
in Fig. 8.
otes
䊳 The OTT CBS does not have a switch for switching the unit on and off. As soon
as power is supplied, the OTT CBS is ready for operation.
䊳 Each time the power supply is attached, the piston pump operates for approx.
400 strokes (approx. 5 minutes running time).
6.2 Connecting the OTT CBS to any data logger using the SDI-12
interface
䡵 Connect the OTT CBS to an S I-12 input of the external data logger. Follow
the data logger handbook as you do this. See Fig. 8 for the assignments. The
maximum cable length is 100 m* !
* OTT CBS connected to the data logger; no bus operation; otherwise 70 m
6.3 Connecting the OTT CBS to any data logger using the RS-485
interface (SDI-12 / Modbus protocol)
䡵 Connect the OTT CBS to an RS-485 input (S I-12 or Modbus protocol) on the
external data logger. Refer to the data logger manual for more details. The
connection assignment can be found in Figure 8. The maximum cable length is
– S I-12 protocol: 1000 m
– Modbus protocol: 100 m
6.4 Connecting the OTT CBS to any data logger using the
4 … 20 mA interface
䡵 Connect the OTT CBS to a 4 … 20 mA input of the external data logger.
Follow the data logger handbook as you do this as well as chapter 6.5 of these
instructions). See Fig. 8 for the assignments.
Maximum cable length: ependent on the level of supply voltage and the load
impedance (load resistance). Make sure that the ohmic resistance of the connect-
ing cable added to any load impedance does not exceed the maximum permitted
load resistance (see chapter 6.5 for details). In any case, the upper limit for the
cable length is 1000 m.
䡵 With depth measurement: ensure that IP switch 4 is set to "ON".
13

6.5 Determining the maximum load resistance at the 4 … 20 mA
interface
The load resistance connected to the OTT CBS (load impedance + ohmic resis-
tance of connecting cable) must not exceed a specific maximum value. This value
depends on the level of the supply voltage of the OTT CBS. If the load resistance is
greater, the loop current* can no longer be evaluated. Smaller load resistances
are allowed.
* Current at 4 … 20 mA interface fed in (controlled) by OTT CBS (=
^measured value)
䡵 Read off the maximum load resistance for your power supply from the
following diagram. Alternatively, you can calculate the maximum load resis-
tance using the following formula:
RLoad (max) = (Usupply – 7.75 V)/0.02275 A
Example: Power supply 18 Volt →max. load resistance 450 Ohm.
The OTT CBS delivers a loop current corresponding to the measured value for
a load resistance of up to 450 Ohm.
䡵 imension the connected electrical circuit accordingly. Check the input
resistance of the connected peripheral device for this purpose.
Fig. 9: iagram to determine the
maximum load resistance as a
function of the power supply.
Minimum power supply: 10 V
Maximum power supply: 30 V
Resistor tolerance: 0.1 %/15 ppm.
10 15 20 25 30 U
V
100
0
200
300
400
500
600
700
800
R
Ω
900
1000
Example
14

7 Activating the purge function
On the front of the OTT CBS there is a "Pump" membrane button (see Fig. 10).
Pressing the button activates the purge function for as long as it is pressed. The
"Status" LE lights for approx. 2 seconds. With an activated purge function, the
CBS pumps a large amount of air through the measuring tube for the required time
period (see also chapter 11). The purge function can also be activated via an S I-
12 command.
ote: Press the membrane button for at least one second as otherwise the error
memory is called and displayed at the "Status" LE .
Membrane button
Fig. 10: Activating purge function manually
on the OTT CBS with membrane button.
15

The OTT CBS has a service interface with an eight-position IP switch. This is
located behind a cover on the base of the OTT CBS (see Figure 1). The following
operating parameters can be set with them:
䊳IP 1, 2, 3 Set serial interface type (S I-12 / RS-485)
䊳IP 4 Setting measurement type as level or depth measurement*
䊳IP 5 + 6 Scaling measuring range *
䊳IP 7 Setting metric or imperial system (m/mbar or feet/psi) *
䊳IP 8 Setting measurement type as water level or pressure
measurement *
* these settings only affect the 4 … 20 mA interface.
8.1 Setting the serial interface type
With IP 1 … 3 select the type of S I-12 interface of the OTT CBS (screw terminal
strip B; contacts 1 to 4). Note that only one of the interfaces at a time can be used
(4 ... 20 mA, S I-12 or RS-485; no parallel operation of interfaces).
Possible serial interface types
䊳 S I-12 interface (S I-12 protocol)
䊳 RS-485 interface without termination (S I-12 protocol / Modbus protocol)
Use this setting if multiple OTT CBS are connected in parallel to one RS-485
cable (bus operation) for all OTT CBS except the last device at the end of the
bus.
䊳 RS-485 interface with termination (S I-12 protocol / Modbus protocol)
Use this setting if
– multiple OTT CBS are connected in parallel to the RS-485 cable
(bus operation) for the last device at the end of the bus, or if
– only one OTT CBS is connected to the RS-485 cable.
ote: When using the 4 ... 20 mA interface, the setting of IP 1 ...3 is not rele-
vant. (Exception: If default settings on the OTT CBS are to be changed using the
S I-12 interface during service.)
ON
1 2 3 45678
ON
1 2 3 45678
ON
1 2 3 45678
SDI-12 interface
RS-485 interface
without termination
RS-485 interface
with termination
Fig. 11: Setting the type of S I-12
interface of the OTT CBS.
On the RS-485 interface with termination,
there is an internal 120 Ohm terminating
resistor between the two RS-485 connec-
tions.
8 Adjusting operating parameters using the service
interface
16

8.2 Setting measurement type of the 4 … 20 mA interface to
level or depth measurement
8.3 Scaling the measuring range for the 4 … 20 mA interface
With IPs 5 and 6 you can scale the available measuring range (15 or 30 m) of
an OTT CBS to a smaller range. Where the whole measuring range is not required,
this has the advantage that a higher resolution for the 4 … 20 mA interface can
be achieved. Example: For 2 m water level change 16 mA measuring range is
available ( IP switches 5 + 6 = OFF).
ON
1 2 3 45 6 7 8
ON
1 2 3 45 6 7 8
Level Measurement
Depth Measurement
Fig. 12: Setting measurement type level
or depth measurement of the OTT CBS
(4 … 20 mA interface).
ON
1 2 3 4 5 6 7 8
ON
1 2 3 4 5 6 7 8
ON
1 2 3 4 5 6 7 8
ON
1 2 3 4 5 6 7 8
15 m / 50 ft
1.5 bar / 25 psi
(not scaled)
30 m / 100 ft
3 bar / 50 psi
(not scaled)
8 m / 25 ft
0.8 bar / 12 psi
15 m / 50 ft
1.5 bar / 25 psi
4 m / 12 ft
0.4 bar / 6 psi
8 m / 25 ft
0.8 bar / 12 psi
2 m / 6 ft
0.2 bar / 3 psi
4 m / 12 ft
1.5 bar / 6 psi
Standard +
USGS specification
30 m measuring
range
CBS version
Fig. 13: Scaling the measuring
range of the OTT CBS
(4 … 20 mA interface).
17

8.4 Setting the measuring system for the 4 … 20 mA interface
8.5 Setting measurement type of the 4 … 20 mA interface to
water level or pressure measurement
8.6 Factory setting of the operating parameters
䊳 S I-12 interface; level measurement; measuring range not scaled; metric sys-
tem; water level measurement.
ON
12345678
ON
12345678
Metric measurement system: m+ mbar
Imperial measurement system: feet + psi
Fig. 14: Setting the measuring
system of the OTT CBS
(4 … 20 mA interface).
ON
12345678
ON
12345678
Water level measurement
Pressure measurement
Fig. 15: Setting measurement type to
water level or pressure measurement
(4 … 20 mA interface).
ON
12345678
Fig. 16: Factory setting of the
operating parameters.
18

9 SDI-12 commands and responses
Communication with the OTT CBS is carried out using a standardised serial S I-12 interface. In this technical documentation,
you will find a detailed description of the S I-12 commands implemented in the S I-12 transfer protocol.
Further information on the S I-12 standard can be found in the document "S I-12; A Serial- igital Interface Standard for
Microprocessor-Based Sensors; Version 1.4" (see website "www.sdi-12.org").
All advanced, manufacturer-specific S I-12 commands on the OTT CBS begin with "O" for OTT. With these commands it is
possible to configure the OTT CBS, for example using the "Transparent mode" on a data logger or with the OTT USB/S I-12
interface accessory.
Conventions for measured value formats
p– Sign (+,–)
b– Figure (before decimal point); output without leading zeroes
e– Figure after the decimal point
a<CR><LF> – Service Request
! – ends a command
9.1 Overview of SDI-12 commands
Standard commands
䊳 a! Acknowledgement active
䊳 aI! Send identification
䊳 aAb! Change sensor address
䊳 ?! Query sensor address; factory setting: 0
䊳 a ! Start measurement
䊳 aD0! Send data
䊳 a C! Start measurement and request CRC (Cyclic Redundancy Check)
䊳 aC! Start concurrent measurement (simultaneous measurement with multiple sensors on one bus line)
䊳 aCC! Start concurrent measurement and request CRC
䊳 aV! Start system test
Meta data commands
䊳 aI ! etermine response to associated a !command (does not start measurement)
aI C! … a C!
aIC! … aC!
aICC! … aCC!
䊳 aIV! etermine response to associated aV! command (does not start system test)
䊳 aI _001! Query meta data for measured value 1, 2 and 3; measured value in aD0! after a !
aI _002!
aI _003!
aI C_001! … a C!
aI C_002!
aI C_003!
aIC_001! … aC!
aIC_002!
aIC_003!
aICC_001! … aCC!
aICC_002!
aICC_003!
䊳 aIV_001! Query meta data for response to "Perform system test" command
19

Advanced commands (manufacturer-specific)
䊳 aOX <value>! Set measuring time
aOX ! Read measuring time
Factory setting: +50 s
䊳 aOXC<value>! Set cycle time
aOXC! Read cycle time
Factory setting: +60 s
䊳 aOAA<value>! Set "level" or "depth" measuring mode
aOAA! Read measuring mode
Factory setting: +0 ➝"Level" measuring mode
䊳 aOAB<value>! Set offset value for level/depth measurement (S I-12/RS-485 interface)
aOAB Read offset
Factory setting: +0.000 m
䊳 aOAC<value>! Set reference value for level/depth measurement (S I-12/RS-485 interface)
aOAC Read reference value
Factory setting: +0.000 m
䊳 aOXR<value>! Set mean water density
aOXR! Read mean water density
Factory setting: +0.999972 kg/dm3
䊳 aOXT<value>! Set mean water temperature
aOXT Read mean water temperature
Factory setting: +3.980000 °C
䊳 aOXK<value>! Set correction factor for pressure/level value
aOXK! Read correction factor for pressure/level value
Factory setting: +1.000000
䊳 aOXG<value>! Set local acceleration due to gravity
OXG! Read local acceleration due to gravity
Factory setting: +9.80665 m/s2
䊳 aOPC<Wert>! Set status of 4 … 20 mA interface
aOPC! Read status
Factory setting: +0 ➝4 … 20 mA interface disabled
䊳 aOSU<value>! Set unit for level/pressure measured values
aOSU! Read unit
Factory setting: +0 ➝Unit m
䊳 aOST<value>! Set unit for temperature measured values
aOST! Read unit
Factory setting: +0 ➝Unit °C
䊳 aOOV! Read firmware version
䊳 aOXP<value>! Activate/deactivate purge function
Factory setting: +0 ➝Purge function deactivated
䊳 aOZY<value>! Set S I-12 interface version
aOZY Read version
Factory setting: +1 ➝Current version activated
䊳 aOPF<value>! Set status of Modbus protocol
aOPF Read status
Factory setting: +0 ➝Modbus protocol deactivated
䊳 aOPG<value>! Modbus: Set bus address
aOPG Read bus address
Factory setting: +1
䊳 aOPH<value>! Modbus: Set transmission speed
aOPH Read transmission speed
Factory setting: +9600 bit/s
20