ELPRO 905 series, 905U-1, 905U-3, 105S-1, 105S-2 User Manual

Radio/Serial Telemetry Module User Manual

Thank you for your selection of the 905 module for your telemetry

needs. 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 905 enjoys a long life,

double check ALL your connections with

the user’s manual

before turning the power on.

Page 2 © March 2000

Contents

FCC Notice:

This user’s manual is for the ELPRO 905 series radio telemetry module. This device complies with
Part 15.247 of the FCC Rules.

Operation is subject to the following two conditions:

1) This device may not cause harmful interference and

2) This device must accept any interference received, including interference that may cause

undesired operation.

This device must be operated as supplied by ELPRO Technologies Pty Ltd. Any changes or
modifications made to the device without the written consent of ELPRO Technologies Pty. Ltd.
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 ELPRO Technologies. Please contact
ELPRO Technologies 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 General Docket 79-144 on March 13, 1996.

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 electical 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 .

man_905_2.0.doc Page 3

Radio/Serial Telemetry Module User Manual

How to Use This Manual
To receive the maximum benefit from your 905 product, please read the Introduction, Installation

and Operation chapters of this manual thoroughly before putting the 905 to work.
Chapter Four Configuration explains how to configure the modules using the Configuration

Software available. For configuration using the on-board switches, refer to the separate 905 Switch
Configuration Manual.

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 and Chapter Seven specifies
the Warranty and Service conditions.

The foldout sheet 905 Installation Guide is an installation drawing appropriate for most
applications.

Warning !

1. For 905U modules, a radio licence is not required in most countries, provided the module is
installed using the aerial and equipment configuration described in the 905 Installation
Guide. Check with your local 905 distributor for further information on regulations.

2. For 905U modules, operation is authorised 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. The 905 intelligent
communications protocol aims to correct communication errors due to interference and to
retransmit the required output conditions regularly. However some delay in the operation of
outputs may occur during periods of interference. Systems should be designed to be
tolerant of these delays.

3. To avoid the risk of electrocution, the aerial, aerial cable, serial cables and all terminals of
the 905 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 905 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 905 module is not suitable for use in explosive environments without additional

protection.

Page 4 © March 2000

Contents

CONTENTS

CHAPTER ONE INTRODUCTION.....................................................................................................................................7

1.1 G ENERAL....................................................................................................................................................................7

CHAPTER TWO INSTALLATION...................................................................................................................................10

2.1 G ENERAL..................................................................................................................................................................10

2.2 AERIAL INSTALLATION (ERROR! BOOKMARK NOT DEFINED.U UNITS ONLY)...............................................10

2.2.1 Dipole aerial. ...............................................................................................................................................11

2.2.2 Three element Yagi aerial.........................................................................................................................12

2.2.3 Collinear (3dB) aerial. ..............................................................................................................................13

2.3 POWER SUPPLY.......................................................................................................................................................13

2.3.1 AC Supply.....................................................................................................................................................14

2.3.2 DC Supply.................................................................................................................................................... 14

2.3.3 Solar Supply................................................................................................................................................ 15

2.3.4 Multiple Modules........................................................................................................................................15

2.3.5 24V Regulated Supply............................................................................................................................... 16

2.4 INPUT / OUTPUT .....................................................................................................................................................16

2.4.1 Digital Inputs (Error! Bookmark not defined.-1 and Error! Bookmark not defined.-2)...............16

2.4.2 Digital Outputs (Error! Bookmark not defined.-1)..............................................................................17

2.4.3 Digital Outputs (Error! Bookmark not defined.-2 and Error! Bookmark not defined.-3)............19

2.4.4 Analogue Inputs (Error! Bookmark not defined.-1 and Error! Bookmark not defined.-2).......... 19

2.4.5 Analogue Outputs (Error! Bookmark not defined.-1 and Error! Bookmark not defined.-3).......20

2.4.6 Pulse Input (Error! Bookmark not defined.-1).....................................................................................20

2.4.7 Pulse Inputs (Error! Bookmark not defined.-2)...................................................................................20

2.4.8 Pulse Output (Error! Bookmark not defined.-1)...................................................................................21

2.4.9 Pulse Output (Error! Bookmark not defined.-3)...................................................................................21

2.4.10 RS232 Serial Port.......................................................................................................................................21

2.4.11 RS485 Serial Port.......................................................................................................................................22

CHAPTER THREE.............................................................................................................................................OPERATION

25

3.1 POWER-UP AND NORMAL OPERATION...............................................................................................................25

3.1.1 Communications ......................................................................................................................................... 25

3.1.2 Change of state conditions.......................................................................................................................27

3.1.3 Analogue Set-points...................................................................................................................................29

3.1.4 Start-up Poll................................................................................................................................................ 30

3.1.5 Communications Failure (CF)................................................................................................................. 30

3.1.6 Resetting Outputs........................................................................................................................................30

3.2 SYSTEM DESIGN TIPS.............................................................................................................................................30

3.2.1 System Dynamics.........................................................................................................................................30

3.2.2 Radio Channel Capacity...........................................................................................................................31

3.2.3 Radio Path Reliability...............................................................................................................................31

3.2.4 Design for Failures.....................................................................................................................................32

CHAPTER FOUR.....................................................................................................................................CONFIGURATION

33

4.1 INTRODUCTION .......................................................................................................................................................33

4.2 EASY CONFIGURATION USING DEFAULT SETTINGS.........................................................................................34

4.3 ERROR! BOOKMARK NOT DEFINED. CONFIGURATION SOFTWARE ...............................................................36

4.3.1 Hardware Requirements............................................................................................................................36

4.3.2 Installation...................................................................................................................................................37

4.3.3 Software Operation.................................................................................................................................... 37

4.3.4 Changing User Options..................................................................................................................................41

4.3.5 Programming / Downloading Configuration........................................................................................43

man_905_2.0.doc Page 5

Radio/Serial Telemetry Module User Manual

CHAPTER FIVE SPECIFICATIONS................................................................................................................................45

CHAPTER SIX..................................................................................................................................TROUBLESHOOTING

49

6.1 DIAGNOSTICS CHART .............................................................................................................................................49

6.2 SELF TEST FUNCTIONS ..........................................................................................................................................49

6.2.1 Input to Output Reflection (105-1 only)................................................................................................49

6.2.2 Radio Testing using Tone Reversals....................................................................................................... 50

6.2.3 Diagnostics menu........................................................................................................................................50

CHAPTER SEVEN......................................................................................................................WARRANTY & SERVICE

56

APPENDIX A SYSTEM EXAMPLE...................................................................................................................................57

Page 6 © March 2000

Chapter One Introduction

Chapter One INTRODUCTION

1.1 General

The 905 range of telemetry modules has been designed to provide standard “off-the-shelf”
telemetry functions, for an economical price. Telemetry is the transmission of signals over a long
distance via a medium such as radio or twisted-pair wire. Although the 905 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.

The unit can monitor and control the following types of signals:

Digital on/off signals

Example outputs - motor run, siren on
Example inputs - motor fault, tank overflow, intruder alarm

Analogue continuously variable signals (0-20mA)

Example outputs - tank level indication, required motor speed
Example inputs - measured tank level, actual motor speed

Pulse frequency signals

Examples - electricity metering, fluid flow

Internal Status signals

Examples - analogue battery voltage, power status, solar panel status and low
battery status.

The unit will monitor the input signals and transmit the signal information by radio or RS485 twisted
pair to another 905 module. At the remote unit, the signals will be reproduced as digital, analogue
or pulse output signals. The 905 also provides analogue set points, so that a digital output may be
configured to turn on and off depending on the value of an analogue input. The pulse I/O transmits
an accumulated value and the pulses are reliably recreated at the remote unit regardless of ‘missed’
transmissions. The actual pulse rate is also calculated and is available as a remote analogue output.

This manual covers the 905U and 105S modules. We have provided a summary on all products
available in the 905 telemetry range, below.

• 905U-1, 905U-2 and 905U-3 modules have UHF radio and serial communications. The

modules differ only in their input/output (I/O) design, and are compatible, i.e. they can be used to
communicate signals to each other in the same network.

• 105S-1, 105S-2 and 105S-3 modules have only serial communications. All other specifications

are as per the 905U-1, 2 & 3 modules. The 105S modules are compatible with 905U modules.

• 105M-1, 105M-2 and 105M-3 modules are for interfacing to MAP27 trunked radio systems.

man_905_2.0.doc Page 7

Radio/Serial Telemetry Module User Manual

These modules can transmit I/O messages hundreds of kilometres via the trunked radio system.
105M-1, 2 and 3 modules differ only in their input/output (I/O) design, and can interface to
105U and 105S modules. For more information, refer to the 105M User Manual.

• The 905U-C module provides an interface between host devices such as PLC’s or SCADA

computers, and a radio telemetry system comprising 905U and 105S radio telemetry modules.
The 905U-C allows 905U/105S modules to act as remote wireless I/O for the host devices.
For more information, refer to the 905U-C User Manual.

Product naming convention:

1 0 5 a - x

where a is:
U = UHF radio + RS232/RS485 serial S = RS232/RS485 serial only
M = MAP27 trunked radio interface
and x is:
1 = Input / Output module 2 = Input module ( includes one output)
3 = Output module C= Interface module

905U-1 105S-1 905U-2 105S-2 905U-3 105S-3

Radio ü ü ü

Serial ü ü ü ü ü ü

Digital Inputs (DI)

Digital Outputs (DO)

Analogue Inputs (AI)

Analogue Outputs (AO)

Pulse Inputs (PI)

Pulse Outputs (PO)

Comments

PI is DI 1. PO is

separate to DO.

4 4

4 (relay) 1 (FET) 8 (FET)

2 (4-20mA) 6 (0-20mA)

2 (4-20mA) 8 (0-20mA)

1 (100Hz) 4 (1x1KHz, 3x100Hz)

1 (100Hz) 4 (100 Hz)

PI’s are the same as

DI’s.

PO’s are the same as

DO’s (DO 1-4).

The module includes power supply, microprocessor controller, input/output circuits, RS485/232
serial port, and a UHF radio transceiver - no external electronics are required. The 905U version
has both radio and serial port communications. The 105S version does not have a radio and has
only serial communications. The 905U radio frequency has been selected to meet the requirements

Page 8 © March 2000

Chapter One Introduction

of unlicensed operation for remote monitoring and control of equipment. That is, a radio licence is

not required for the 905 modules in many countries. See Chapter Five Specifications for details.
Input signals connected to a 905 module are transmitted to another 905 module and appear as

output signals. These input signals may also be configured to appear as “inverted” signals on the
output. A transmission occurs whenever a "change-of-state" occurs on an input signal. A "change­of-state" of a digital or digital internal input is a change from "off" to "on" or vice-versa. A "change­of-state" for an analogue input, internal analogue input or pulse input rate is a change in value of the
signal of 3% (configurable from 0.8 to 50 %).

In addition to change-of-state messages, update messages are automatically transmitted on a regular
basis. The time period may be configured by the user for each input. This update ensures the
integrity of the system.

Pulse inputs are accumulated as a pulse count and the accumulated pulse count is transmitted
regularly according to the configured update time.

The 905 modules transmit the input/output data as a data frame using radio or serial RS485 as the
communications medium. The data frame includes the "address" of the transmitting 905 module and
the receiving 905 module, so that each transmitted message is acted on only by the correct receiving
unit. Each transmitted message also includes error checking to ensure that no corruption of the data
frame has occurred due to noise or interference. The 905 module with the correct receiving
"address" will acknowledge the message with a return transmission. If the original module does not
receive a correct acknowledgement to a transmission, it will retry up to five times before setting the
communications fail status of that path. In critical paths, this status can be reflected on an output on
the module for alert purposes. The module will continue to try to establish communications and
retry, if required, each time an update or change-of-state occurs.

A 905 telemetry system may be a complex network or a simple pair of modules. An easy-to-use
configuration procedure allows the user to specify any output destination for each input.

The maximum number of modules in one system is 95 modules communicating by radio. Each of
these modules may have up to 31 other modules connected by RS485 twisted pair. Modules may
communicate by radio only, by RS485 only or by both RS485 and radio. Any input signal at any
module may be configured to appear at any output on any module in the entire system.

Modules can be used as repeaters to re-transmit messages on to the destination module. Repeaters
can repeat messages on the radio channel, or from the radio channel to the serial channel (and serial
to radio). Up to five repeater addresses may be configured for each input-to-output link.

The units may be configured using switches under the plastic cover on the front of the unit or by
using a PC connected to the RS232 port. The default configuration is defined in Section 4.2 Easy

Configuration Using Default Settings , and software configuration is defined in Section 4.2 905
Configuration Software. Several standard configurations are also available. These are described
in the separate 905 Switch Configuration Manual, available from your 905 distributor.

man_905_2.0.doc Page 9

Radio/Serial Telemetry Module User Manual

Chapter Two INSTALLATION

2.1 General

The 905 module is housed in a rugged aluminium case, suitable for DIN-rail mounting. Terminals are
suitable for cables up to 2.5 sqmm in size.

Normal 110/220/240V mains supply should not be connected to any input terminal of the

905 module. Refer to Section 2.3 Power Supply.
Before installing a new system, it is preferable to bench test the complete system. Configuration

problems are easier to recognise when the system units are adjacent. Following installation, the
most common problem is poor communications on the radio channel or the serial channel. For radio
modules, problems are caused by incorrectly installed aerials, or radio interference on the same
channel, or the radio path being inadequate. If the radio path is a problem (i.e. path too long, or
obstructions in the way), then higher performance aerials or a higher mounting point for the aerial
may fix the problem. Alternately, use an intermediate 905 module as a repeater.

For serial modules, poorly installed serial cable, or interference on the serial cable is a common
problem.

The foldout sheet 905 Installation Guide provides an installation drawing appropriate to most
applications. Further information is detailed below.

Each 905 module should be effectively earthed via a "GND" terminal on the 905 module - this is to
ensure that the surge protection circuits inside the 905 module are effective.

2.2 Aerial Installation (905U units only)

The 905 module will operate reliably over large distances. The distance which may be reliably
achieved will vary with each application - depending on the type and location of aerials, the degree
of radio interference, and obstructions (such as hills or trees) to the radio path. See the 905
Installation Guide for expected ranges in your country. Where it is not possible to achieve reliable
communications between two 905 modules, then a third 905 module may be used to receive the
message and re-transmit it. This module is referred to as a repeater. This module may also have
input/output (I/O) signals connected to it and form part of the I/O network - refer to Chapter 4
Configuration of this manual.

An aerial must be connected to each 905 module using the BNC female connector which protrudes
though one of the end plates.

To achieve the maximum transmission distance, the aerials should be raised above intermediate
obstructions so the radio path is true “line of sight”. Because of the curvature of the earth, the
aerials will need to be elevated at least 5 metres above ground for paths greater than 5 km (3 miles).
For short distances, the modules will operate reliably with some obstruction of the radio path.

Page 10 © March 2000

Chapter Two Installation

Obstructions which are close to either aerial will have more of a blocking affect than obstructions in
the middle of the radio path. For example, a group of trees around the aerial is a large obstruction,
and the aerial should be raised above the trees. However if there is at least 100 metres of clear path
before a group of trees, the trees will have little affect on the radio path.

An aerial should be connected to the module via 50 ohm coaxial cable (eg RG58 or RG213)
terminated with a male BNC connector. The higher the aerial is mounted, the greater the
transmission range will be, however as the length of coaxial cable increases so do cable losses. For
use on unlicensed frequency channels, there are several types of aerials suitable for use. It is
important aerial are chosen carefully to avoid contravening the maximum power limit on the
unlicensed channel - if in doubt refer to an authorised service provider.

Connections between the aerial and coaxial cable should be carefully taped to prevent ingress of
moisture. Moisture ingress in the coaxial cable is a common cause for problems with radio systems,
as it greatly increases the radio losses. We recommend that the connection be taped, firstly with a
layer of PVC Tape, then with a vulcanising tape such as “3M 23 tape”, and finally with another
layer of PVC UV Stabilised insulating tape. The first layer of tape allows the joint to be easily
inspected when trouble shooting as the vulcanising seal can be easily removed.

Where aerials are mounted on elevated masts, the masts should be effectively earthed to avoid
lightning surges. Although the 905 module is fitted with surge protection, additional surge
suppression devices are recommended if lightning surge problems are experienced. If the aerial is
not already shielded from lightning strike by an adjacent earthed structure, a lightning rod may be
installed above the aerial to provide shielding.

2.2.1 Dipole aerial.

A unity gain dipole is the normal aerial for use on unlicensed channels. As it does not provide any
gain, then the power transmitted from the aerial will be the same as the power out of the module,
and hence will not exceed the permitted power of the unlicensed channel.

For marginal radio paths, the following lengths are the recommended maximum for the coaxial
cable to the dipole aerial. RG58 -10 metres RG213 - 20 metres. Note that this applies to
marginal paths only - if the radio path has a strong radio signal, then longer lengths of cable ( and
hence more cable loss) can be tolerated. If more than 20 metres of cable is required for a marginal
path installation, then a low loss cable such as 10D-FB, or a higher gain aerial should be used.
Dipole aerials should be mounted vertically, at least 1 metre away from a wall or mast.

man_905_2.0.doc Page 11

Radio/Serial Telemetry Module User Manual

2.2.2 Three element Yagi aerial.

A 3 element Yagi aerial provides approx 4 dB of gain. This may be used to compensate for coaxial
cable loss for installations with marginal radio path. Note that these aerials should not be used if the
coaxial cable lengths are less than the following minimum lengths, otherwise the power transmitted
from the aerial will exceed the power permitted for the unlicensed channel.

RG58 10 metres
RG213 20 metres.

Yagi aerials are directional. That is, they have positive gain to the front of the aerial, but negative
gain in other directions. Hence Yagi aerials should be installed with the central beam horizontal and
must be pointed exactly in the direction of transmission to benefit from the gain of the aerial. Also
note that Yagi aerials normally have a drain hole on the folded element - the drain hole should be
located on the bottom of the installed aerial.

The Yagi aerials may be installed with the elements in a vertical plane (vertically polarised) or in a
horizontal plane (horizontally polarised). For a two station installation, with both modules using
Yagi aerials, horizontal polarisation is recommended. If there are more than two stations
transmitting to a common station, then the Yagi aerials should have vertical polarisation, and the
common (or “central” station should have a dipole or collinear (non-directional) aerial.

Page 12 © March 2000

Chapter Two Installation

2.2.3 Collinear (3dB) aerial.

A 3dB collinear aerial may be used in the same way as a 3 element Yagi to compensate for the
losses in long lengths of coaxial cable. This type of aerial is generally used at a central site with more
than one remote site or at a repeater site. The collinear aerial looks similar to the dipole, except
that it is longer.

2.3 Power Supply

The 905 power supply is a switch-mode design which will accept either AC or DC supply. The 905
module may also be powered from a solar panel without an external solar regulator.

The 905 module accepts supply voltages in the following ranges :

12 - 24 volts AC RMS or 15 - 30 volts DC at the “supply” terminals, or

10.8 -15 volts DC at the “battery” terminals.

man_905_2.0.doc Page 13

Radio/Serial Telemetry Module User Manual

2.3.1 AC Supply

The AC supply is connected to the "SUP1" and "SUP2" terminals as shown below.

+

-

The AC supply should be "floating" relative to earth. A 220-240/16 VAC mains "plug-pack" is
available for mains applications.

2.3.2 DC Supply

For DC supplies, the positive lead is connected to "SUP1" and the negative to "GND". The positive
side of the supply must not be connected to earth. The DC supply may be a floating supply or
negatively grounded.

+

-

The 905 module may also be powered from an external 11 - 15 VDC battery supply without the
need for a "normal" supply connected to "SUP1". This external battery supply is connected to
"BAT+" and "GND" terminals. The positive lead of the external supply should be protected by a 2A
fuse.

Upon failure of the normal supply, the 905 module may continue to operate for several hours from a
backup battery. The 905 module includes battery charging circuits for charging up to a 12 AHr
sealed lead acid battery. The battery is connected to the "BAT+" (positive) and "GND" (negative)
terminals. The positive lead from the battery should be protected with a 2A fuse, installed as near to
the battery terminal as possible. On return of main supply, the unit will switch back to mains
operation, and recharge the battery. To provide adequate current to recharge the backup battery,
an AC supply of 15V minimum or a DC supply of 17V minimum must be used. Typically, a 6 AHr
battery will supply the 905 for 1 - 3 days, depending on I/O loads.

Page 14 © March 2000

Chapter Two Installation

2.3.3 Solar Supply

The 905 power supply also includes a 12 V solar regulator for connecting 12V solar panels of up to
30W, and solar batteries of up to 100AHr. The unit may not be powered from a solar panel without
a battery. An 18W solar panel is sufficient for most solar applications. The size of the solar battery
required depends on the I/O used. Batteries are sized for a number of sunless days with 50%
battery capacity remaining as follows:

No. of sunless days = Battery capacity (AHr) x 0.5
Module load (A) x 1.2 x 24
The Module load depends on the I/O connected and can be calculated as follows:

Module Load(A) = 0.07 + (0.01 x No. of DI’s) + (0.025 x No. of DO’s)

+ (2 x Analogue loop load).

The analogue loop load is the total signal current for the AI’s and AO’s which are powered from the
internal 24V supply. Externally powered loops are not included in this.

The solar panel is connected to the "SOL" (positive) and "GND" (negative) terminals and the battery
connected to the "BAT+" (positive) and "GND" (negative) terminals. Solar panels must be installed
and connected as per the panel manufacturer's instructions. The positive lead of the battery should
be protected by a 2A fuse installed as near as possible to the battery terminal.

Where a solar panel larger than 30W is required, an external solar regulator should be
used.

2.3.4 Multiple Modules

Where more than one module is installed at the one location, a shared power supply and battery
may be used, provided the total load does not exceed the power supply.

man_905_2.0.doc Page 15

Radio/Serial Telemetry Module User Manual

The internal power supply of the 905 module can supply a maximum 12V load of 700mA. In order
to achieve this, the input power supply must be above 15VAC or 17VDC. Using these figures, it
can be determined whether there is enough supply for more than one module - allow 100mA for
recharging a battery.

For example, assume there is a 905U-01 module and a 105S-01 module at the same location. The
total I/O at the location is 3 analogue inputs, 6 digital inputs and 4 digital outputs. The total load will
be :-

TYPE OF LOAD LOAD mA

905U-01 quiescent 70
105S-01 quiescent 45
6 DI @ 10 mA 60
3 AI @ 20mA x 2 120
4 DO @ 25mA 100
Battery charging 100
TOTAL 495

So both modules could be powered from one power supply and one battery, provided the external
supply voltage is more than 15VAC or 17VDC.

2.3.5 24V Regulated Supply

Each 905 module provides a 24V DC regulated supply for analogue loop power. The supply is
rated at 150mA, and should only be used for analogue loops.

2.4 Input / Output

2.4.1 Digital Inputs (905-1 and 905-2)

The 905-1 and 905-2 modules each provide four digital inputs with 5000 volt opto-isolation,

Page 16 © March 2000

Chapter Two Installation

suitable for voltage free contacts (such as mechanical switches) or NPN transistor devices (such as
electronic proximity switches). Contact wetting current of approximately 5mA is provided to
maintain reliable operation of driving relays.

Each digital input is connected between the appropriate "DI" terminal and common "COM". Each
digital input circuit includes a LED indicator which is lit when the digital input is active, that is, when
the input circuit is closed. Provided the resistance of the switching device is less than 200 ohms, the
device will be able to activate the digital input.

For pulse inputs, refer to Section 2.4.6.

2.4.2 Digital Outputs (905-1)

The 905-1 module provides four normally open voltage-free relay contacts, rated at AC3
250V/2A, 120V/5A ; AC1 - 250V/5A ; DC - 30V/2A, 20V/5A. These outputs may be used to
directly control low-powered equipment, or to power larger relays for higher powered equipment.
When driving inductive loads such as AC relays, good installation should include capacitors (e.g.
10nf 250V) across the external circuit to prevent arcing across the relay contacts. For DC inductive
loads, flyback diodes should be used to drive DC relays.

Digital outputs may be configured to individually turn off if no command message is received to that

man_905_2.0.doc Page 17

Radio/Serial Telemetry Module User Manual

output for a certain period. This feature provides an intelligent watch dog for each output, so that a
communications failure at a transmitting site causes the output to revert to a known state. See
section 4.4 Changing User Options for further details.

The output circuit is connected to the appropriate pair of "DO" terminals. Each digital output circuit
includes a LED indicator which is lit when the digital output is active.

Page 18 © March 2000

Chapter Two Installation

2.4.3 Digital Outputs (905-2 and 905-3)

The digital outputs on the 905-2 and 905-3 modules are transistor switched DC signals, FET
output to common rated at 30VDC 500 mA. The 905-2 provides one digital output and the 905­3 provides eight digital outputs. The first four DO’s on the 905-3 module are also the pulse outputs

- that is, the first four DO's can be either digital outputs or pulse outputs. The function of each of
these outputs may be configured individually. For a description of pulse outputs, refer to Section

2.4.7.
Digital outputs may be configured to individually turn off if no command message is received to that

output for a certain period. This feature provides an intelligent watch dog for each output, so that a
communications failure at a transmitting site causes the output to revert to a known state. See
Chapter 4 Configuration for further details.

The output circuit is connected to the appropriate pair of "DO" terminals. Each digital output circuit
includes a LED indicator which is lit when the digital output is active.

2.4.4 Analogue Inputs (905-1 and 905-2)

The 905-1 module provides two 4 - 20 mA DC analogue inputs for connecting to instrument
transducers such as level, moisture, pressure transducers, etc. The 905-2 module provides six 0 ­20 mA DC analogue inputs. Note that the inputs on the 905-2 module will measure down to 0mA,
so they can also be used for zero based signals such as 0 - 10 mA.

Each analogue input has a positive and negative terminal, and may be placed at any point in the
current loop, as long as neither input rises above the 24 volt supply level. Each input has a loop
resistance of less than 250 ohms and zener diode protection is provided against over-voltage and
reverse voltage, however additional protection may be required in high voltage or noisy
environments.

A 24VDC supply is available on the 905 module for powering the analogue transducer loops. In
this case, the analogue loop should be connected between a "AI 1-" terminal and "COM" ( for the
first analogue input) or "AI 2-" ( for the second analogue input), and so on for other inputs. The
positive terminal ("AI 1+" or "AI 2+", etc) should be connected to "+24V".

man_905_2.0.doc Page 19

Radio/Serial Telemetry Module User Manual

Externally powered loops may be connected by connecting the input between "AI 1+" and “AI 1-”
for analogue input 1 or "AI 2+" and “AI 2-” for analogue input 2, and so on for other inputs.
Analogue Input 1 "AI 1+" may also be configured to control a high/low analogue set-point. See
Chapter 4 Configuration for further details.

Common mode voltage may be -0.5V to 27V. Shielded cable is recommended for analogue I/O
loops to minimise induced noise and Radio Frequency Interference (RFI). The shield of the cable
should be connected to earth at one of the cable only. The use of shielded wiring inside an
enclosure containing a 905 module is also recommended.

2.4.5 Analogue Outputs (905-1 and 905-3)

The 905-1 module provides two 4 - 20 mA DC analogue outputs for connecting to instrument
indicators for the display of remote analogue measurements. The 905-3 module provides eight 0 ­20 mA DC analogue outputs. Each analogue output is a "sink" to common.

+

-

A 24VDC supply is available on the 905 module for powering the analogue output loop (max
external loop resistance 1000 ohms). In this case, the analogue loop is connected between a "+24V"
terminal and "AO 1" ( for the first analogue output) or "AO 2" (for the second analogue output),
and so on for the other output signals.

Externally powered loops to 27 VDC may be connected by connecting the output between the
"AO” terminal (positive) and the "COM" terminal (negative). Zener protection of analogue outputs
provides protection against short periods of over-voltage but longer periods may result in module
damage. Note that the 905 common is connected internally to ground and no other point in the
analogue loop should be grounded.

Analogue outputs may also be configured to individually turn off (0 mA) if no command message is
received to that output for a certain period. . See Chapter 4 Configuration for further details.

2.4.6 Pulse Input (905-1)

For the 905-1 module, digital input 1 may be configured as a pulse input (max rate 100 Hz, min. off
time 5 ms). In this mode, both the pulse rate and the pulse count are available for mapping to a
remote output. The pulse rate may appear at any analogue output on the remote unit, while the
pulse count can appear at a Pulse Output on another 905-1 or Digital Output on a 905-3 unit. The
pulse input should be connected in the same way as a digital input.

2.4.7 Pulse Inputs (905-2)

Page 20 © March 2000