ATM-155-Fibre

Introduction

The ATM-N1-155-Fibre module holds up to 6 x KCSonet Nodes, a single media converter, DC-DC converter power supplies for the media converter. Also included are dual redundant over voltage protection for each SONET Node. The module is cooled by high performance low noise 35 mm dual ball bearing fan units.

The ATM-N1-155 module is predominately used to connect the KCSonet nodes and analogue input modules in the form a stand-alone rack system to a data logger PC across a single string fibre network. Multiple systems can be connected together using an ATM switch is required and this allows the synchronisation between all inputs on the systems to be maintained

Specifications

the specifications for the ATM-N1-155-Fibre module are as follows:

Internal Power Supplies

The following supplies are available within the ATM-N1-155-Fibre Module:

SONET Nodes Supply

• External AC/DC required; 6 - 14 V DC. 0.5A - 14 Watts Max (fully populated)
• unregulated; standard for KCSonet Nodes

Fibre Optic Media Converter

• Standard SC Optical Fibre terminators
• 9 V DC 10Watt Supply - Fibre Media Converter

Over Voltage protection

• Dual Redundant Over Voltage Protection for each KCSonet Node

Specification for the Media Converter

The following information is taken directly from the data sheet available for the media converter. The media converter is not manufactured by Keynes Controls and its details are listed to demonstrate the operating characteristics of the system. In practice most third party fibre optic media converters can be fitted to the unit.

Network Properties

Physical Dimensions

Height = 239.9 mm
Width = 68 mm
Depth = 220 mm

Figure 3 shows the systems assembly and PCB used within the ATM-N1-155 module. Each ATM-N1-155 module supports up to 6 of KCsonet nodes and any combination of the analogue input cards such as the AD2416F 16 channel voltage input unit.

On the bottom right hand side of the PCB are shown the DC-DC converts used to supply the KCsonet nodes and the Media converter and the dual redundancy over voltage regulators.

Each of the KCSonet nodes are powered by individual channel dual redundant pair of over voltage regulators. This feature ensures that the failure of the power supply to any KCSonet node does not effect the operation of any other adjacent node. The over voltage regulators also contain thermal cutout and will shutdown should any of the KCSonet nodes develope a short circuit condition.

The KCSonet nodes operate mounted in the ATM-N1-155 module operate in a master slave configuration just as they do when distributed on any other type of ATM network. Assigning of the master node is undertaken initially by virtue of the positions of the KCSonet nodes position on the PCB.

Figure 4 shows a typical network schematic for the ATM-N1-155 module. The drawing shows how the input modules are connected to the KCSonet nodes and via the media converter and fibre network back to a data logger PC. An ATM data switch has been shown in order to demonstrate how two fibre optic networks can be connected together to increase the network transmission distances, however it is possible to simply connect the fibre optic cable from the media converter directly to a suitable connection on the ATM interface card as long as it supports a Fibre interface.

The example in Figure 4 shows the ATM-N1-155 module connected to a multi-port ATM switch via a fibre optic network. The cards inserted in the ATM switch can connect a multimode or single mode fibre to the ATM switch or multiple data logger computers together. Large ATM switches can be used to connect together different types of ATM networks together to form large scale integrated systems. As long as multiple network strings are networked together via a switch then all channels are synchronised.

High Speed RS422 Data Link

As shown, each of the analogue input modules connects to a separate KCSonet node by a high speed RS422 serial interface. The KCSonet node controls the timing of the data within the cards and forms the data packets broadcast across the network.

Internal Network Connection

The KCSonet nodes are connected together on the ATM-N1-155 PCB in exactly in the same manner as they would be on a distributed ATM network.

Master/Slave Input Operations

Initially the analogue input card adjacent to the ATM-N1-155 is the master card and provides timing information to all other cards in the rack. If this card is removed, which can be done while the systems are in operation then the software within the KCSonet nodes will automatically assign a new master and no timing information is lost. The input cards remain synchronised.

Figure 5 shows a typical rack system solution that can be assembled using the ATM-N1-155 module. These rack systems are generally deployed remotely across a fibre optic network. The ATM-N1-155 module is shown as the 1st card installed on the left had side of the rack system. All of the input modules connect through to the ATM-N1-155 via the back plane cable harness fitted to the rear of the rack system. For ease of use the Fibre optic network cable fits into the front of the media converter. Depending upon the type of media converter fitted the RJ45 terminates the KCSonet node network.

The system in Figure 5 has been customised for a client and offers fixed sample rates of 6 and 12 KHz upon activation of the sample rate selection switch. In practice the standard sample rates are 0 to 96 KHz/channel in steps of 8 KHz depending upon the number of channels on a network and nodes to be used. In practice any sample rate can be achieved but in some cases data points are ignored.

When in operation the analogue input modules indicate that full system synchronisation is being maintained by use of the on board status LED's seen at the bottom of each module. Each analogue input module contains status LEDs used to indicate the different modes of operation. The Sync LEDs on each input card are illuminated and stay in synchronisation with each other while data is being acquired. If for any reason the ATM network fails and the timing signals are lost, then the Sync Status LED on each card will appear to be flashing randomly compared to its adjacent neighbor.