Greenspan SDI-12 User manual

SDI-12 Converter
4 - 20mA and RS232 Versions
User
Manual
Version 1.03

[phone]
Greenspan Customer Service
Technical Support When You Need It
The correct choice of sensor should be supported by professional advice to
ensure long term success in the field. Greenspan Technical Services is
dedicated to customer support and provides assistance in the selection,
installation, deployment and commissioning of sensors with a full range of
consulting services.
A full technical support and field advice service can be accessed by ringing
Customer Service on [phone] between 8am - 6pm, 5 days a week.
All requests for information will be serviced within 24 hours.
All Greenspan products are designed, developed and manufactured in Australia,
can be supplied at short notice and be customised to meet most requirements.
Warranty Details
All Greenspan products are covered by a 12-month warranty.
All warranty service will be turned around in 7 working days or less or contact
will be made with customer to discuss delay.
The sensor should not be dismantled unless under instruction from Greenspan.
Incorrect handling will void the warranty.

Contents
1 INTRODUCTION
Overview...........................................................................…….… 1
2 THE HARDWARE
Converter Design......................................................................... 2
SDI-100 (4-20mA)...........................................................………... 2
SDI-200 (RS232, Smart))............................................................. 2
SDI-300 (RS232, Sonde)..........................................................…. 2
Power Requirement.....................................................………….. 3
3 COMMUNICATIONS PROTOCOL
SDI-12 Control Sequence....................................................……. 4
4 INSTALLATION
Electrical Bus Connection........................................................... 5
Wiring Connection to SDI-100................................................…. 6
Connection to SDI-200................................................................. 8
Connection to SDI-300................................................................. 8
General Installation...........................................................……... 8
5 TROUBLESHOOTING.................................................................………. 9
6 SPECIFICATIONS
SDI-100/200/300 Specification..................................................... 10
APPENDIX
Setup and Testing Example...................................................….. 11
Supported Converter Commands.....................………………….. 12

INTRODUCTION 1
Overview
The Greenspan SDI-12 Converter, model numbers SDI-100, SDI-200 and SDI-
300 are designed to allow connection of standard Greenspan sensors to the SDI-
12 serial/digital network widely used in the hydrological and field monitoring
industry.
SDI-12 allows multiple connection of sensors to a single data logging recorder,
transmitting at 1200 baud over distances up to 60 metres (200 ft) between each
converter unit and data logger.
Note that cable lengths from sensor to converter unit have been tested
up to 300 metres and are not subject to the SDI-12 limit of 60 metres.
The converter is packaged in a durable, robust, weatherproof housing and,
depending on the model, is either hardwired or uses cable connectors for sensor
connection and serial cable in/out. Power is supplied to the converters and
sensors via the SDI-12 cable from the data logger.
A Sensor Input
B SDI In
C SDI Out
D Sensor On Indicator
E Vent fitting (for pressure sensors)
SDI-100 Converter SDI-200/300 Converter
(for 4-20mA sensors) (for RS232 sensors)
A
B C
A
B
D
D
3
E E C
3
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HARDWARE 2
Converter Design
There are two basic models of SDI-12 converter, one for 4-20mA sensors and one
for RS232 sensors. A third variation allows for connection to Sondes.
SDI-100 (4-20mA)
The Greenspan SDI-100 converter consists of the following primary elements:
• Three cable entry/exit ports with weatherproof cable seals
• Microprocessor controlled signal conditioning and serial input/output
circuit
• ‘Sensor On’ indicator
• Weatherproof housing to IP65
• Vent fitting for desiccant packs, for use with gauge pressure sensors.
Any 4-20mA output sensor may be connected to this unit by simple screw
terminals within the housing. The analog signal (current loop) is converted to a
digital signal and output as SDI-12 format serial data.
SDI-200 (RS232 for Smart)
The Greenspan SDI-200 converter consists of the following primary elements:
• Three Conxall entry/exit connectors mounted on housing, SDI Out
includes weather cap protection if output not used.
• RS232 signal processing (microprocessor controlled) and serial
input/output circuit
• ‘Sensor On’ indicator
• Weatherproof housing to IP65
• Vent fitting for desiccant packs, for use with gauge pressure sensors
This model receives RS232 serial data and converts it to SDI-12 serial data
format. The sensors used with this converter include microprocessor and logging
capability, therefore data retrieval and control functions may be activated from
the remote SDI-12 logger. It is not necessary to open this unit as all connections
are external.
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SDI-300 (RS232 for Sonde)
The Greenspan SDI-300 converter is the same as the SDI-200 except for the
inclusion of a 31 pin Connector to suit the Sonde.
Power Requirement
All units require +9 to +15V DC power supplied to them from the data logger via
the network cable. The current drawn in standby mode is 10mA and less than
100mA (typically 40mA) per unit including sensor power, when reading
measurements. The maximum load on the bus must be less than 500mA.
Transient protection (against induced electromagnetic effects e.g., lightning) on
both the SDI-12 serial lines and the +12V line is provided on all units.
Supply polarity protection is provided by a polyfuse device and is auto resetting.
The design complies with EMC standards for radiation interference.
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COMMUNICATIONS PROTOCOL 3
SDI-12 Control Sequence
SDI-12 data loggers and sensors communicate by an exchange of ASCII
characters on the serial data line. The data logger sends a break to wake up the
sensors on the data line. A break is a continuous spacing on the data line for at
least 12 milliseconds. The data logger then sends a command. The sensor, in
turn, returns the appropriate response. Each command is for a specific sensor.
The first character of each command is a unique sensor address that specifies
which sensor the logger wants to communicate with. Other sensors on the SDI-
12 bus ignore the command and return to low-power standby mode. When a
data logger commands a sensor to start its measurement procedure, the logger
does not communicate with any other sensor until the data collection from the
first sensor is complete.
A typical recorder/sensor measurement sequence proceeds as follows:
Step 1. The data logger wakes all sensors on the SDI-12 bus with a break.
Step 2. The logger transmits a command to a specific, addressed sensor,
instructing it to make a measurement.
Step 3. The addressed sensor responds within 15 milliseconds and
returns the following information:
a) The maximum time before the measurement data is ready.
b) The number of data values it will return.
Step 4. If the measurement is immediately available, the logger transmits
a command to the sensor instructing it to return the
measurement(s). If the measurement is not ready, the data logger
waits for the sensor to send a request to the logger, to indicate
that it is ready. The logger then transmits a command to get the
data.
Step 5. The sensor responds, returning one or more measurements.
There is a maximum of nine addresses that can be accessed on the network and
these are numbered 00 to 09.
Note that it is possible to setup for dual logging if the sensor type is a
Greenspan Smart sensor with onboard logger. The SDI-12 data logger can
request readings at any time from the Smart sensor independently of the
readings being logged by the sensor.
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INSTALLATION 4
Electrical Bus Connection
The SDI-12 bus is the cable that connects multiple SDI-12 devices. This cable
has three conductors:
1 Ground Line
2 Serial Data Line
3 +12V Line
Figure 1 shows the SDI-12 bus connecting one data logger with two SDI-12
converter units and their sensors.
Serial Data Line
SDI-12
Data
Logger +12V Line
Ground Line
4-20mA
Sensor
SDI-200
Converter
SDI-100
Converter
Earth
RS232
Sensor
Figure 1, The SDI-12 Bus
The maximum load that may be applied to the SDI-12 bus is 200K ohms when
the transmitter is off and between 1K and 2K ohm when the transmitter is on.
The ground line must be connected to the circuit ground and the earth ground at
the data logger. The sensor ground must be connected to the ground line, but
not normally to its own ground.
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Wiring Connection to Model SDI-100
Connection to the SDI-100 is by internal terminal block as most sensors are
supplied with bare wire terminations suitable for data logger connection.
Please refer to Figure 2 for connection:
Sensor
Cable
SDI In SDI Out
Cable Clamp
SDI-100
Base
1 2 3 4
1. +12V, Red
2. Input 1, Blue
3. Input 2, White
4. Ground, Green
Note: Colours are for
Greenspan products
only.
1 2 3 1 2 3
1. Ground, Green
2. Serial Data, Blue
3. +12V, Red
Figure 2, SDI-100 Wiring
1. Undo four case screws and remove top cover.
2. Insert sensor cable through sensor port. For gauge type pressure sensors,
a vent tube is required to be fitted. The cable vent tube is cut and pushed
into joiner provided. The millipore filter attached to the vent tube for
shipping can be used on the SDI-100 if desiccant packs are not required.
Spare desiccant packs, (PVS100) are available from Greenspan for
attachment to Luer fitting. Please refer to figure 3.
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Luer fitting
gland
Loop 150mm
PVC Tube
20mm joiner
sensor vent tube
Figure 3, Vent Fitting
3. Refer to Figure 2 for connection and clamp wires to terminal block.
4. Insert remaining cables through SDI In port and SDI Out port (for
multiple connections any 4-6 mm OD, 3 core cable is suitable).
5. Refer to Figure 2 for connection to terminal block.
6. Tighten cable clamps on all three cable ports, replace top cover and
tighten screws.
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