FTS SDI-PT-KEL User manual

EXTREME ENVIRONMENTS. EXTREMELY SIMPLE.
SDI-PT-KEL
SDI-12 Submersible Pressure Transducer
User Manual
For SDI-PT-SS-KEL and SDI-PT-TT-KEL
1.800.548.4264 | www.ftsinc.com
700-SDI-PT-KEL-Man Rev 4 05 Feb 2020

Contact Information
Canadian Headquarters:
1065 Henry Eng Place
Victoria, BC | V9B 6B2 | Canada
www.ftsinc.com
Toll-free: 1.800.548.4264
Local: 250.478.5561
Technical support portal: http://support.ftsinc.com
Email: [e-mail]

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Contents
1.1 GENERAL DESCRIPTION ...................................................................................................................................................1
1.2 WIRING ...................................................................................................................................................................................2
1.3 OPERATION...........................................................................................................................................................................2
1.4 CONFIGURATION................................................................................................................................................................2
1.5 MAINTENANCE ....................................................................................................................................................................2
1.5.1 Changing the Desiccant .......................................................................................................................................2
1.5.2 Cleaning a Clogged Nose Cap............................................................................................................................3
2.1 PRIOR TO INSTALLATION.................................................................................................................................................4
2.2 HANDLING THE CABLE AND SENSOR.........................................................................................................................4
2.3 SITE SELECTION...................................................................................................................................................................5
2.4 INSTALLING THE SENSOR................................................................................................................................................5
2.4.1 INSTALLATION WITH AN FTS AXIOM DATALOGGER .................................................................................5
3.1 GENERAL INFORMATION.................................................................................................................................................6
3.2 NOTATION FOR SDI-12 COMMANDS..........................................................................................................................6
3.3 ERROR DISPLAYS ................................................................................................................................................................7
3.4 MEASUREMENT COMMANDS........................................................................................................................................8
3.4.1 Concurrent Measurement Commands...........................................................................................................9
3.4.2 Continuous Measurement (R-Commands) ...................................................................................................9
3.4.3 Send Data.................................................................................................................................................................10
3.5 GENERAL SDI-12 COMMANDS ....................................................................................................................................10
3.5.1 Acknowledge Active............................................................................................................................................11
3.5.2 Send Identification ...............................................................................................................................................11
3.5.3 Change Address.....................................................................................................................................................11
3.5.4 Address Query........................................................................................................................................................11
3.5.5 Start Verification....................................................................................................................................................12
3.6 EXTENDED SDI-12 COMMANDS (X-COMMANDS) ...............................................................................................12
3.6.1 Pressure.....................................................................................................................................................................13
3.6.2 Temperature ...........................................................................................................................................................14

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GENERAL
1.1 GENERAL DESCRIPTION
The SDI-12 Submersible Pressure Transducer (SDI-PT-KEL) is designed for freshwater level
measurements. Typical applications include lakes, streams, wells, agricultural water level/flow, and
tanks.
The SDI-PT-KEL can be supplied with either a stainless steel (SDI-PT-SS-KEL) or a titanium (SDI-PT-TT-
KEL) case and with either a bayonet connector for use with FTS Axiom Dataloggers or with flying
leads for use with other data loggers.
A vent tube incorporated in the cable vents the sensor diaphragm to the atmosphere. This
eliminates the need to compensate for changes in barometric pressure. Care must be given to
prevent the vent tube from being pinched or crushed which can result in erroneous readings.
Ensure the cable is free from obstructions and kinks.
To prevent water vapor from entering the inner cavity of the sensor, which can cause erroneous
data and damage to the sensor, the vent tube opening terminates inside a desiccated vent tube
enclosure.
Figure 1-1: SDI-PT-KEL
Military
bayonet
connector
Vent tube enclosure
SDI-PT-KEL

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1.2 WIRING
The SDI-PT-KEL can be supplied with a bayonet connector for use with FTS Axiom Dataloggers or
with flying leads for use with other data loggers.
Braided shield wire is connected to the transducer housing. For lightning protection to function
properly the shield wire must be connected to a good earth ground.
1.3 OPERATION
The SDI-PT-KEL is an SDI-12 device and is powered by the +12 V DC power supply on the SDI-12 bus.
For details on the SDI commands used by the sensor, see Chapter 5 - SDI Commands.
1.4 CONFIGURATION
The SDI-PT-KEL is shipped with default address zero (0). If more than one SDI-12 sensor is on the
same bus it may be necessary to change the address. Refer to Chapter 4 for instructions on the
command used to set the sensor’s address.
1.5 MAINTENANCE
Every visit make a visual inspection of the wiring and physical conditions looking for damage to the
sensor and cable, or sensor blockages. Check the vent tube enclosure humidity monitor card to
determine if the desiccant requires changing. Verify that the air inlet is free from debris.
Please contact FTS technical support (see manual front pages) if the unit ceases to operate properly.
1.5.1 Changing the Desiccant
When the humidity monitor card indicates a 40% level of humidity, the desiccant must be changed.
In order to do so the vent tube enclosure must be opened using a Phillips or slot screwdriver. Only
do this in a clean, dry environment.
Replace the desiccant bag and place a new humidity indicator card on top of the wiring, ensuring the
40% section of the humidity level indicator is visible. Replace the screws and hand tighten.
Desiccant bags and humidity indicator cards can be ordered through FTS:
ITEM
PART NUMBER
2 g desiccant bag
11438
Humidity indicator card
11672
WIRE COLOUR
(flying leads)
BAYONET
PIN
FUNCTION
Red A +12 V DC power supply
White B Data
Black C Ground
Blue N/A RS485A
Yellow N/A RS485B
Bayonet connector

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1.5.2 Cleaning a Clogged Nose Cap
Erroneous readings can result from a clogged nose cap.
To clean the transducer’s nose cap you will need a soap, scum and hard-water stain remover and
three containers of a suitable size. Fill one container with the stain remover, another with a mixture
of the cleaner and fresh water, and the third container with fresh water.
Hold the cable approximately 6 inches from the transducer and gently stir in each of the containers
for 20-30 seconds in the following order: cleaning solution, cleaning solution-water mix, and finally
the fresh water. Then wipe dry with a soft cloth.
WARNING! Under no circumstances should the membrane or pressure input port be
probed with any object. Damage to the sensing membrane is permanent and, in
most cases, requires repair or replacement.

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INSTALLATION
2.1 PRIOR TO INSTALLATION
Prior to installing, inspect the SDI-PT-KEL and its cable for damage. The cable should not have any
kinks or cuts as these can render the vent tube useless. Ensure the humidity monitor card in the
vent enclosure box indicates low humidity levels. If not, replace the desiccant and card (see section
1.5.1)
2.2 HANDLING THE CABLE AND SENSOR
The sensor can fail if the cable is damaged so exercise care when handling the sensor and cable.
The cable can also be damaged by abrasion, sharp objects and rodents so ensure it is positioned
away from potential hazards and securely attached.
•Do not touch or probe the pressure sensing membrane with anything. Damage to
the sensing membrane will require repair or replacement.
•Do not twist, crimp or compress the cable as this can damage the pressure tube.
oThe cable should not be bent to a radius less than 1 inch.
oIf using a compression fitting to secure the cable as it enters a junction box, do not
over tighten the fitting
•Do not drop the SDI-PT-KEL, allow it to strike a hard surface forcefully, or allow it to “free
fall” as this may damage the sensor.
•Do not allow the cable to drag over sharp edges or be abraded.
•Avoid contact with corrosive chemicals.
•The sensor could be damaged if encased in frozen liquid.
If the sensor is suspended, to prevent cable strain and stretch, use split mesh cable grips. This is
especially important to relieve strain at the attachment point between the cable and the sensor.
Figure 2-1: Split Mesh Cable Grip Example
Attach the strop to a
hard point to relieve
strain.

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2.3 SITE SELECTION
FTS recommends that the SDI-PT-KEL be installed in a stilling well or through a protective, rigid
conduit to which it is attached using a conduit fitting. Ideally, there should be a solid structure (ie:
bridge footing or dam face) to which the conduit can be attached.
If the installation precludes the previous installation guidelines, care should be taken to protect the
cable and anchor the sensor.Select a location where the stream bed and banks are stable and are
free from elements which may damage the cable (sharp protuberances, crushing hazards etc.). If
the site does not have a structure which can be used, the sensor and cable should be fed through a
conduit for protection and to provide a method of anchoring the sensor.
2.4 INSTALLING THE SENSOR
For best results the SDI-PT-KEL should be mounted vertically
in a stilling well or attached to a rigid conduit with a conduit
fitting which is integral with the transducer.
The SDI-PT-KEL should be installed at a fixed depth, mounted
vertically below the lowest expected water stage. If not
mounted vertically, there may be an offset. In order to
compensate for the offset, measure the output with no
pressure applied prior to connecting to your display, PLC, or
controller. Use the measured value for your zero point.
Ensure the placement is such that potential water pressure
will never exceed the sensor’s pressure range, 2 times the
pressure range (see Chapter 5 - Technical Specifications).
The sensor and cable should be secured to a solid and stable
surface in order to maintain the desired depth and to
minimize cable damage due to abrasion.
2.4.1 INSTALLATION WITH AN FTS AXIOM DATALOGGER
If installing the SDI-PT-KEL sensor with an FTS Axiom Datalogger, the sensor must be configured for
the Datalogger using the Stage sensor extension. DO NOT use the SDI-PT sensor extension as that is
specific to the FTS SDI-PT sensor. Refer to the Axiom Operator’s Manual for details.

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SDI-12 COMMUNICATION
3.1 GENERAL INFORMATION
SDI-12 protocols are based on Version 1.3. 1
All characters are printable ASCII characters except the response of an SDI-12 sensor which ends
with <CR><LF>2and sometimes the CRC code includes a non-printable ASCII character.
The default address of an SDI-12 sensor is always ‘0’. The sensor’s address can be changed to an
address from ‘1’ to ‘9’, from ‘A’ to ‘Z’ or from ‘a’ to ‘z’.
The option of continuous measurements is only supported with a specific extended command (X-
command).
A <CR><LF> is returned for an R-Command or with CRC switched on. It is a<CRC> <CR><LF>, unless
continuous mode is switched on and configured over the extended command aXR!
Note the following:
•the “a” in each command should be replaced with the sensor’s address
•every command must terminate with an exclamation mark (!)
•the CRC3is added at the end of the message for commands with CRC
•the measurement command must be followed by a Send Data command (aD0!) to view the
data
This chapter will provide basic direction on general SDI-12 Commands. Detailed direction can be
found in accordance with the document found at footnote 5.
This chapter will also provide information of some useful SDI-12 commands specific to the SDI-PT-
KEL. Detailed information on all SDI-12 communication protocols specific to the Keller Acculevel can
be found in the Keller document, “SDI-12 communication Protocol”4.
3.2 NOTATION FOR SDI-12 COMMANDS
SDI commands are strings of characters sent to the SDI sensor by a data logger, data collection
platform or other SDI-12 master. The sensor takes action based on the command that was sent (ie.
starting a measurement) and then replies to the command with a string of characters.
Note that as cable length increases, so do noise levels which can interfere with the digital
measurement communications between the sensor and the data logger. Significant noise levels can
1In accordance with “SDI-12 A Serial-Digital Interface Standard for Microprocessor-Based Sensors ver 1.3”. Refer to:
http://www.sdi-12.org
2Carriage Return Line Feed
3Cyclic Redundancy Check
4https://www.kelleramerica.com/manuals-and-software/manuals/communication_protocol_SDI-12.pdf

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result in excessive SDI-12 retries, incorrect data, or even no response. SDI-12 commands (like aMC!)
which add a CRC5can greatly improve incorrect data issues.
The following format is used to specify the different parts of an SDI-12 command and sensor reply.
Mandatory elements are in bold:
Item Meaning Text
representation
Sensor Address First character of a command* and
response. Valid values 0-9, a-z, A-Z.
a
Command literal Part of a command that must be
reproduced literally as it appears;
X
Command
parameter
Part of a command that must be filled in
with an appropriate value.
xxx
Optional
parameter
Part of a command that can be omitted if
not needed. The brackets [ ] are not
included in the command.
[xxx]
Floating point
number
Number representing a measurement value
or command parameter. If a command
parameter it will be bolded and may be
marked as optional.
u.uuuuu or
[u.uuuuu]
Replies As above but not bolded u.uuuuu
Command
Terminator
The last character of a command !
* except the address query
3.3 ERROR DISPLAYS
The following error values are displayed for the D and R commands if the continuous measurement
mode is switched on with the corresponding extended command.
Field
Value Displayed
Meaning
Pressure +9999999
1) Overflow (readings +10% of the specified range)
2) Pressure element damaged
-9999999
Underflow (readings -10% of the specified range)
Temperature +9999999 Overflow
-9999999 Underflow
nan Damaged or unreadable sensor value +9999999
5Cyclic Redundancy Check – an error detecting code used to detect accidental changes to raw data.