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The basic TX-L unit features:

  • 4 digital inputs
  • 2 analogue inputs
  • 1 RS485 port
  • 24v 2W auxiliary power supply
  • GSM modem.

An Ethernet port can be fitted as an option when ordering.

Up to two expansion cards can be added; these cards may either add an additional 4 analogue or 8 digital inputs.

 

Configuration

Analogue Inputs

Digital Inputs

Base Unit (No Cards)

2

4

Base Unit + 1 Digital Card

2

12

Base Unit + 2 Digital Cards

2

20

Base Unit + 1 Analogue Cards

6

4

Base Unit + 2 Analogue Cards

10

4

Base Unit + 1 Analogue Card + 1 Digital Card

6

12

 

The diagram above shows a TX-L with one analogue expansion card and one digital expansion card installed.

Contact MPEC for more information regarding the purchase of additional cards.


Block diagram and isolation policy

All of the green lines in the diagram below denote an isolation barrier. Every block of the TX-L shown is isolated from every other block and from the case.

All of the individual analogue inputs are isolated from each other and from the auxiliary power supplies.

Isolation barriers are to a minimum of 10M Ohms at 1,000V DC.

The thick green lines denote two expansion cards that may be fitted.  In this case one analogue and one digital card are shown.



Power supply - AC units only

The “universal input” power supply accepts any voltage from 85 to 264V ac.

A suggested connection is shown below.

 CAUTION: The MINIFIT power connector is not designed to be mated whilst live. Mate this connector prior to energising the unit.

 

The power supply is internally isolated from earth and the rest of the SA380TX-L. Power can therefore be taken directly from the signalling 110V supply and no additional isolating transformer is required.

The earth pin of the MINIFIT socket is connected to the case only.

 

The TX-L does not have internal battery backup and so is not suitable for monitoring equipment such as level crossings where there is a long battery backup time, unless either:

  • The TXL is powered from the level crossing battery (not currently permitted in the UK), or
  • An external UPS (uninterruptible power supply) is provided with enough standby reserve to power the TX-L as long as the level crossing.

 

An internal 2A slow-blow fuse is provided. The external fuse must also be a minimum of 2A slow-blow (often marked T2A).

Slow blow is required because of the inrush current of the power supply at start-up.

Power consumption and external equipment

Typical power consumption of the unit is between 2-10W.  If the unit has to supply external equipment, for instance current clamps or network routers, then power consumption will rise accordingly.

Maximum rated consumption is 40W.  At 110V, this is 0.36A.


 

Power supply - DC units only

The power supply input accepts a DC voltage from 9 to 18VDC.

12VDC is the optimal voltage that should be applied.

A suggested connection is shown below.

 CAUTION: The MINIFIT power connector is not designed to be mated whilst live. Mate this connector prior to energising the unit.

     

DC Powered units have not been tested in accordance with the European EMC directive, therefore such units do not comply with European CE marking directive.

The power supply is internally isolated from earth and the rest of the SA380TX-L.

The earth pin of the MINIFIT socket is connected to the case only.

 

The TX-L does not have internal battery backup and so is not suitable for monitoring equipment such as level crossings where there is a long battery backup time, unless either:

  • The TXL is powered from the level crossing battery (not currently permitted in the UK), or
  • An external UPS (uninterruptible power supply) is provided with enough standby reserve to power the TX-L as long as the level crossing.

 

An internal 5A slow-blow fuse is provided. The external fuse must also be a minimum of 5A slow-blow (often marked T5A).

Slow blow is required because of the inrush current of the power supply at start-up.

Power consumption and external equipment

Typical power consumption of the unit with no sensors attached is between 2-10W.  If the unit has to supply external equipment, for instance current clamps or network routers, then power consumption will rise accordingly.

Maximum rated consumption is 40W.  At 12V, this is 3.34A.

CAUTION: The unit can support a maximum load of 2W per analogue channel or a total load of 10W per unit in the DC configuration. For example, if a constant load of 2W is applied to each analogue channel, a total of 5 channels can be utilized. If a constant load of 1W is applied to each analogue channel, all 10 analogue channels may be utilized.

Digital inputs

Four digital inputs are provided to monitor spare contacts of signalling relays.

These inputs are connected as follows:

All of the terminals marked “C” are connected together internally.

This allows easy wiring to signalling relays using twisted pair cable, as specified in railway standards.

Internal resistors limit the sense current to a few milliamps at 24V.

The digital inputs are fully isolated to a minimum of 10M Ohm at 1,000V DC.

This isolation ensures that the inputs are fully separate from earth, the logger’s internal logic and the analogue inputs.

Digital inputs must never be connected into a live circuit (e.g. across a contact that is already in use by the signalling system).

They must only ever be connected to spare relay contacts.

Extra care must be taken when monitoring geographical type relay interlockings, as there are internal connections within the relay sets which are not obvious just from the plugboard positions. 

We recommend that full signal works testing procedures are used for geographical interlockings, not just Instrumentation Engineer.

Also the original interlocking diagrams should be updated – if overlay diagrams are used, there is a risk if other persons change the interlocking circuitry in future.

These inputs are for use with volt-free relay contacts only. Do not apply voltages to these inputs.


Analogue inputs

Analogue inputs are designed to accept industry standard 4-20mA sensors.

Many types of external sensor are available with a 4-20mA output, including current clamps, temperature sensors, pressure sensors and voltage transducers.

Each analogue card has four isolated channels, which are capable of powering 4-20mA current clamps. The terminals are:

  • 24: 24V out
  • S: Signal input
  • 0: 0V

The input impedance between S and 0 terminals is 200ohms.

The maximum output power of the 24V sensor power feed is 2W, or 83mA, per analogue input.

 

CAUTION: The unit can support a maximum load of 2W per analogue channel or a total load of 10W per unit in the DC configuration. For example, if a constant load of 2W is applied to each analogue channel, a total of 5 channels can be utilized. If a constant load of 1W is applied to each analogue channel, all 10 analogue channels may be utilized.

 

Auxiliary power out

Each card can be factory fitted with an auxiliary power output on request.

For instance a +12V output could be used to power an Ethernet router or a fibre-Ethernet converter, or to power sensors that require their own power supply.

Analogue inputs must never be connected directly to any signalling supplies or circuits.

This includes (but is not limited to) B24, B50, BX110, track circuits and signalling line circuits.

 

The simplest 4-20mA sensors only have two connections and take their power entirely from the loop. Others have three or four wires.

The four wire types use a separate signal and power ground to avoid interference between the power supply and measurement currents.

Example wiring to the different types is shown below:


RS485 (EbiTrack®)

The isolated RS485 communications port may be used to monitor the Bombardier EbiTrack 200, 300 and 400 range of digital track circuit transmitters and receivers.

Up to eight EbiTrack units may be monitored using a single TX-L using a multi-drop RS485 network.

Configure the network as shown below using twisted pair cable.

Termination resistors are used at each end of the link.

 

The EbiTrack units’ RS485 interface utilises a 9-pin D-sub connector.

The connector must be wired as follows:

  • Pin 1: RS485 Mode Select (Connect to Pin 9)
  • Pin 2: Signal Pair (Connect to RS485 line B)
  • Pin 6: Signal Pair (Connect to RS485 line A)
  • Pin 9: 5V DC (Connect to Pin 1)


Front panel

USB Diagnostics

On-site configuration, diagnostics and data interrogation is performed by connecting a laptop to the TX-L using the supplied USB cable.

The USB port is electrically isolated from the signalling inputs of the TX-L.

Your laptop must be running MPEC’s dPanel software in order to communicate with the TX-L (see Configuration and Diagnostics section).

LED’s

The TX-L front panel features 8 LEDs.

The meaning of these LEDs is detailed in the table below:

LED

Indication

Meaning

Server

Steady On

Last transmission of sample data to the Central Data Server successful.

ServerFast Blink**Device is attempting to connect with the server.
ServerSlow Blink**Transmission to the Central Data Server has recently failed. Device is now in FALLBACK
ServerOffThere is no data connection to the server

Comm

Steady On

Connected to the GSM Network

GSM

Steady On

Modem Powered On

Master/Slave

Slow Alternating Flash (1 sec)

Normal Operation

Master/Slave

Fast Flash (0.25 sec)

Processor Sync Error*

Master/Slave

Steady On or Off

Processor Error

Storage

Blinking

Data Read/Write from database

Storage

Steady On

Database Error

Input

Blinking

Analogue or Digital Input Event Detected

RS485

Blinking

Data Transmit/Receive on RS485 Port

 

 

*It is normal to observe a “Processor Sync Error” during initial boot and during firmware upgrade.

 

** The table describes behaviour in MIMOSA protocol mode. In RailDAQ mode, the following behaviour is observed: The server connection LED will not show fallback, as the timeout is short. During Firmware upgrade over RailDAQ, the server LED will not illuminate. If the device is not configured within Centrix, the server LED will not illuminate, as it cannot transmit samples.

Restart Comms Button

Pressing this button forces the modem to immediately power-cycle and attempt reconnection with the GSM service provider and the central data server.

When connected over Ethernet, any existing connection will be dropped and reinitialised.


GSM antenna

The supplied GSM antenna, unlike many antennas, is an “impedance matched, balanced antenna”.

Such antennas do not need a ground plane reference (such as the metalwork of a location case) to function.

As such they are inherently safer and more immune to interference.

The old-style black, square “puck” antennas previously shipped with SA380TX and SA380TX-L should no longer be used. These are NOT suitable for use at 3G frequencies. Instead a new light-grey antenna is shipped with the units.

This new antenna offers great performance for a compact size at 2G and 3G frequnecy bands. It is also able to be mounted in a similar fashion to the old-style version.

The antenna is to always be fitted to the exterior of the location case or equipment room and connects to the rear of the logger with a screw-fit connector.

A suitable aperture is to be usually found on the side of most location cases.

To mitigate against the unlikely event of a right-side failure, it is recommended that the length of the antenna cable is not altered and that the cable is routed separately to other cabling susceptible to interference, such as EbiTrack track circuit feeds, or SSI data links.

Ethernet

When fitted, the Ethernet card may be used for data transmission and remote accessibility at higher data rates.

Any standard RJ45 UTP network cable may be fitted to this port.

The TX-L can then be connected to your own IT infrastructure using any standard Ethernet switch or router.

In order to fully comply with Railway EMC regulations (radiated emissions) please ensure that an RF choke is clipped around the end of the Ethernet cable (as shown below).

Ethernet Choke part number: Wurth Elektronik 741 717 22

 


 

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