MTL WMO-900S User manual

WMO-900S
Radio Modem
User Guide
INM WMO900S

WMO-900S Radio Modem
Page 2 July 2010
Thank you for your selection of the WMO-900S radio modem.
We trust it will give you many years of valuable service.
ATTENTION!
Incorrect termination of supply wires may
cause internal damage and will void warranty.
To ensure your WMO-900S enjoys a long life,
double check ALL your connections with the user’s manual
before turning on the power.
THIS EQUIMENT IS SUITABLE FOR USE IN CLASS 1 DIVISION 2, GROUPS A, B, C
& D OR NON-HAZARDOUS LOCATIONS.
CAUTION:
For continued protection against risk of fire, replace the internal module fuse only with the same
type and rating.
CAUTION:
To comply with FCC RF Exposure requirements in section 1.1310 of the FCC Rules, antennas
used with this device must be installed to provide a separation distance of at least 20 cm from all
persons to satisfy RF exposure compliance.
DO NOT:
operate the transmitter when someone is within 20 cm of the antenna
operate the transmitter unless all RF connectors are secure and any open connectors are properly
terminated.
operate the equipment near electrical blasting caps or in an explosive atmosphere
All equipment must be properly grounded for safe operations. All equipment should be serviced
only by a qualified technician.

User Manual
INM WMO900S_v1.9a.doc Page 3
FCC Notice:
This user’s manual is for the MTL WMO-900S radio telemetry module. This device complies
with Part 15.247 of the FCC Rules.
Operation is subject to the following two conditions:
This device may not cause harmful interference and
This device must accept any interference received, including interference that may cause
undesired operation.
This device must be operated as supplied by Measurement Technology Limited. Any changes or
modifications made to the device without the written consent of Measurement Technology
Limited (MTL) may void the user’s authority to operate the device.
End user products that have this device embedded must be supplied with non-standard antenna
connectors, and antennas available from vendors specified by Measurement Technology Limited
(MTL). Please contact MTL for end user antenna and connector recommendations.
Notices: Safety
Exposure to RF energy is an important safety consideration. The FCC has adopted a safety
standard for human exposure to radio frequency electromagnetic energy emitted by FCC regulated
equipment as a result of its actions in Docket 93-62 and OET Bulletin 65 Edition 97-01.
Important Notice
MTL products are designed to be used in industrial environments by experienced industrial
engineering personnel with adequate knowledge of safety design considerations.
MTL radio products are used on unprotected license-free radio bands with radio noise and
interference. The products are designed to operate in the presence of noise and interference,
however in an extreme case, radio noise and interference could cause product operation delays or
operation failure. Like all industrial electronic products, MTL products can fail in a variety of
modes due to misuse, age, or malfunction. We recommend that users and designers design
systems using design techniques intended to prevent personal injury or damage during product
operation, and provide failure tolerant systems to prevent personal injury or damage in the event
of product failure. Designers must warn users of the equipment or systems if adequate protection
against failure has not been included in the system design. Designers must include this Important
Notice in operating procedures and system manuals.
These products should not be used in non-industrial applications, or life-support systems, without
consulting MTL first.
1. A radio license is not required in some countries, provided the module is installed using
the aerial and equipment configuration described in the WMO-900S Installation Guide.
Check with your local distributor for further information on regulations.
2. Operation is authorized by the radio frequency regulatory authority in your country on a
non-protection basis. Although all care is taken in the design of these units, there is no
responsibility taken for sources of external interference. Systems should be designed to be
tolerant of these operational delays.

WMO-900S Radio Modem
Page 4 July 2010
3. To avoid the risk of electrocution, the aerial, aerial cable, serial cables and all terminals of
the WMO-900S module should be electrically protected. To provide maximum surge and
lightning protection, the module should be connected to a suitable earth and the aerial,
aerial cable, serial cables and the module should be installed as recommended in the
Installation Guide.
4. To avoid accidents during maintenance or adjustment of remotely controlled equipment,
all equipment should be first disconnected from the WMO-900S module during these
adjustments. Equipment should carry clear markings to indicate remote or automatic
operation. E.g. "This equipment is remotely controlled and may start without warning.
Isolate at the switchboard before attempting adjustments."
5. The WMO-900S module is not suitable for use in explosive environments without
additional protection.
How to Use This Manual
To receive the maximum benefit from your WMO-900S product, please read the Introduction,
Installation and Operation chapters of this manual thoroughly before putting the WMO-900S to
work.
Chapter Four Configuration details the configurations available and explains the diverse
operation of the product in detail.
Chapter Five Specifications details the features of the product and lists the standards to which the
product is approved.
Chapter Six Troubleshooting will help if your system has problems.
The WMO-900S Installation Guide supplied is an installation drawing appropriate for most
applications.

User Manual
INM WMO900S_v1.9a.doc Page 5
CONTENTS
CHAPTER ONEINTRODUCTION...............................................................................7
1.1GENERAL ........................................................................................................................7
1.2TRANSPARENT MODE .....................................................................................................8
1.3CONTROLLED MODE.......................................................................................................9
1.4REPEATER UNITS ..........................................................................................................10
CHAPTER TWOINSTALLATION...............................................................................11
2.1GENERAL ......................................................................................................................11
2.2ANTENNA INSTALLATION .............................................................................................11
2.2.1Dipole and Collinear antennas.................................................................................13
2.2.2Yagi antennas...........................................................................................................13
2.3POWER SUPPLY.............................................................................................................15
2.4SERIAL CONNECTIONS ..................................................................................................15
2.4.1 RS232 Serial Port........................................................................................................15
2.4.2 RS485 Serial Port........................................................................................................16
CHAPTER THREEOPERATION.................................................................................18
3.1POWER-UP AND NORMAL OPERATION ..........................................................................18
3.2SERIAL AND RADIO DATA.............................................................................................18
3.2.1Character Type.........................................................................................................19
3.2.2Serial Data Rate.......................................................................................................19
3.2.3Radio Data Rate.......................................................................................................19
3.3ADDRESSING.................................................................................................................20
3.4TRANSPARENT MODE ...................................................................................................21
3.5TRANSPARENT MODE REPEATERS ................................................................................21
3.6CONTROLLED MODE.....................................................................................................23
3.6.1 Auto-Connect Controlled Mode .................................................................................25
3.6.2 Low Power Auto-Connect Mode...............................................................................26
3.6.3 Single-Connect Controlled Mode..............................................................................26
3.6.4 Fast Operation Controlled Mode ...............................................................................26
3.6.5 CTS/RTS Flow Control .............................................................................................26
3.6.6 Intermediate Repeaters ...............................................................................................26
3.7WHAT OPERATING MODE TO USE ?..............................................................................27
3.7.1Transparent or Controlled Mode?............................................................................27
3.7.2Error Check ?...........................................................................................................28
3.8SERIAL /RADIO RATES .................................................................................................28
3.9RADIO INTERFERENCE ..................................................................................................28
3.10OPERATING PROBLEMS.................................................................................................30
CHAPTER FOURCONFIGURATION...........................................................................31
4.1BEFORE CONFIGURING..................................................................................................31
4.2ADDRESSING.................................................................................................................32
4.3DEFAULT CONFIGURATION ...........................................................................................32
4.4CONFIGURATION PROGRAM..........................................................................................32

WMO-900S Radio Modem
Page 6 July 2010
4.4.1Transparent Mode....................................................................................................34
4.4.2Controlled Mode......................................................................................................34
4.4.3Other Parameters......................................................................................................36
4.5HAYES COMMANDS ......................................................................................................38
4.6CONFIGURATION EXAMPLES.........................................................................................43
4.7SWITCH CONFIGURATION .............................................................................................45
CHAPTER FIVESPECIFICATIONS..............................................................................47
CHAPTER SIXTROUBLESHOOTING.........................................................................49
6.1DIAGNOSTICS CHART....................................................................................................49
6.2TEST FUNCTIONS ..........................................................................................................49
6.2.1Radio Testing - AT&Tx...........................................................................................49
6.2.2Bit Error Rate Test (BER) .......................................................................................50
6.2.3On-line diagnostics..................................................................................................51
APPENDIX A HAYES COMMANDS.............................................................................52

User Manual
INM WMO900S_v1.9a.doc Page 7
Chapter One INTRODUCTION
1.1 General
The WMO-900S radio modem module has been designed to provide flexible and reliable
radio modem functions, at an economical price. Radio modems transmit serial data over a
long distance via radio. The serial data is not changed - the output data is the same as the
input data. Although the WMO-900S is intended to be simple in its application, it also
provides many sophisticated features. This manual should be read carefully to ensure that the
modules are configured and installed to give reliable performance.
Each WMO-900S module will connect to a host device by RS232 or RS485 serial
connection. Examples of host devices are PLC’s, data loggers, intelligent transducers and
computers. The WMO-900S unit can receive data from the host device and transmit this data
by radio to another (or several) WMO-900S module. The other module will recreate the
serial data and output it as either a RS232 or RS485 serial signal. The WMO-900S unit
provides two-way communications - each module can accept serial data and also output serial
data.
The WMO-900S module includes power supply, microprocessor controller, serial
input/output circuits and a 900MHz frequency-hopping spread-spectrum radio transceiver -
no external electronics are required. The WMO-900S radio frequency has been selected to
meet the requirements of unlicensed operation for remote monitoring and control of
equipment. That is, a radio licence is not required for the WMO-900S modules in many
countries. See Chapter Five Specifications for details. The units are configured from a PC
using a “free-ware” configuration package, or from a PC terminal using Hayes commands.
RS232 is an electrical standard format for a full
duplex point-to-point serial connection. RS485
is an electrical standard format for a half-duplex
multidrop serial connection. Up to 32 devices
can communicate on a common RS485 serial
bus. Each WMO-900S unit can only connect to
one serial signal - either RS232 or RS485.
However different modules in the same system
can connect to different types of serial signals. For example, RS232 data from one host
device can be transmitted to a remote WMO-900S unit and output as RS485 data to another
host device.
The WMO-900S has been designed to be flexible enough to cover a wide range of
applications. The user is able to configure many different parameters such that the WMO-
900S unit will connect reliably to different types of host devices. Before the radio modem
can be used, these parameters must be configured. Some of these parameters are :-
Character type - the WMO-900S will accept a variety of 7 or 8 data bit characters
Serial Data Rate - between 1200 and 115200 bits/sec
Radio Data Rate - 19200, 57600 or 115200 bits/sec
Operating mode - transparent mode or controlled mode .
HOST
900S
RS232
HOST
900S
RS485

WMO-900S Radio Modem
Page 8 July 2010
The operation of the WMO-900S radio modem is relatively simple. As data is received at the
serial port, the data is transmitted on the radio channel. Up to 530 bytes of data can be
transmitted in one transmission. The radio transmission commences when the first data byte
is received, and ends when there are no more data bytes in the input buffer, or when the
number of bytes transmitted equals the maximum message length (user configurable - default
530 bytes). If more than 530 bytes is input, the WMO-900S unit will transmit the first 530
bytes, then the next 530 bytes, and so on until all of the data has been transmitted.
Because the radio data rate could be less than the input serial data rate, an input memory
buffer of 2Kbytes is provided. The RS232 connection provides CTS control to prevent the
buffer overflowing. There are no data flow control signals for RS485.
A radio channel cannot provide as secure a data channel as a wired connection. The WMO-
900S uses a radio band with a low level of natural or industrial noise, however there is a
chance of interference from other users of the unlicensed radio channel. We recommend that
the flow of data over the radio channel is controlled by using error detection and
“handshaking” - that is, returning an acknowledgment transmission if a data packet is
received on the radio channel without error. This function can be performed by either the
host devices or the WMO-900S modules. The modules may be configured by the user to
operate in one of two modes. In transparent mode, it is assumed that the host devices control
the flow of data. In controlled mode, the WMO-900S units control the flow of data.
1.2 Transparent Mode
The default configuration of the WMO-
900S modem is transparent mode - the
modules are set in this mode at the factory.
In transparent mode, the WMO-900S
provides no control of the data
transmissions (no error correction). Input
data is simply transmitted by radio and
every other WMO-900S unit in that system
which receives the transmission will output
the data. This mode relies on the host
devices to perform the “handshaking”
function, and re-transmitting serial data if the data is corrupted (no “handshake”). It also
relies on the host devices to include any addressing necessary in the data. In this mode,
modules are not configured with a unit address. Data is “broadcast” - every other WMO-
900S in the system will receive the data and output the data to their individual host devices.
The user may configure the WMO-900S modems to add error checking to each data packet
transmitted - if error checking is configured, data will not be output if it is received without a
correct error-check. This feature provides additional protection against corruption of the data
during the radio transmission. If error-checking is not configured, then the data received by
radio will be output without checking for errors.
HOST
900S
DATA
HOST
900S
DATA
HOST
900S
DATA

User Manual
INM WMO900S_v1.9a.doc Page 9
Transparent mode is “point-to-multipoint” communications, suitable for a host device which
is able to communicate on a multi-drop “bus” type network. An example of an application is
the use of radio modems to extend a PLC RS485 network. The serial messages from the
PLC’s already include PLC addressing and error detection/correction to control the flow of
data.
1.3 Controlled Mode
“Controlled mode” provides “point-to-
point” communications similar to telephone
modems. In controlled mode, the flow of
data is controlled by the WMO-900S units.
Each WMO-900S unit is configured with an
address by the user, and a destination
address for the data to be transmitted to.
Data is transmitted addressed to the
destination module, and only this module
will output the serial data. The source
module will add an error-check (16 bit
CRC) to the data transmitted by radio. The destination module will process the error-check,
and if correct, it will transmit an acknowledgment message (ACK) back to the source
module. If the source module does not receive a ACK, it will re-transmit the data. The
source module will attempt to transmit the data up to five times, until an acknowledgment
(ACK) is received. If an acknowledgment is still not received, then the DCD signal on the
RS232 port will be reset and a alarm message can be sent to the host via the serial port.
An example of an application using controlled mode would be a radio modem link between
an intelligent gas analyzer and a monitoring computer system. Intelligent transducers do not
normally provide addressing or error checking functions - these would be provided by the
WMO-900S modules.
In controlled mode, the destination address may be pre-set, or set on-line by the host device
using “Hayes” commands. Hayes commands are a standard set of commands used with
conventional telephone modems. An example of an application that would use Hayes
command to set destination addresses would be a central computer polling data loggers for
periodic information.
PLC
900S
900S
RS485
PLC
PLC
900S
PLC
HOST
900S
DATA
HOST
900S
NO DATA
HOST
900S
DATA
#1 #2
#3

WMO-900S Radio Modem
Page 10 July 2010
1.4 Repeater Units
A WMO-900S unit may be used as a repeater to re-transmit radio messages. The purpose of
a repeater unit is to extend radio range.
In transparent mode, there can be an unlimited number of repeaters, however with some
conditions (refer to Section 3.5). The repeater in transparent mode will repeat every
transmission it receives.
In controlled mode, up to five repeaters may be configured for any transmission path. The
repeaters are configured by address.
PLC
900S
900S
RS485
PLC
PLC
900S
PLC
REPEATER
900S 900S 900S 900S
900S 900S 900S 900S