Specifications

3U Traffic Outstation Handbook

667/HB/26568/000 Page 25 Issue 15

3.7 ISOLATED MAINS VOLTAGE INPUTS

Each LMU I/O board also supports 10 fully software configurable photo-coupled

mains voltage inputs and a fully configured OMCU provides 30 such inputs. The

function of these inputs is to provide an isolated means of detection of the presence

or absence, of the mains’ signal at the phase drive output terminal blocks. The

following describes the electrical characteristics of a single input.

Each of the inputs again uses an opto Isolator, with additional circuitry, to protect

against reverse voltages, to allow a wide range of mains inputs (including 50 - 0 -

50V AC working for Welsh Office application), also provides current and voltage

limiting.

The High Voltage inputs have the following input electrical characteristic:

Input Impedance:

99kΩ

Absolute Max. Applied Voltage: 580V RMS

Min. Voltage to guarantee signal on condition: 40V RMS

Isolation Voltage: 2500V RMS

3.8 ANALOGUE INPUTS

Each LMU I/O board supports 10 fully software configurable analogue inputs. The

function of these, when connected to appropriate current sensing toroidal

transformers, is to measure the current supply to the lamps, or when connected to the

appropriate voltage monitor transformer, measures the true level of the lamp supply

voltage (dim or bright). The following describes the electrical characteristics of a

single input.

Each of the inputs is multiplexed to an analogue to digital converter. The analogue

inputs are designed to work with both the current sensing transformer that will

measure currents from 0A to 6A peak (and will accept short term current flows of

12A) and the Voltage monitor transformers, which will measure voltages from 0 to

276V.

Current sensing: 6A peak

Voltage monitor: 9V peak to peak @ nominal mains

3.9 COMMUNICATIONS

The processor board contains three serial RS232 communications interfaces and the

first LMU I/O board contains a forth. Each Bus / MOVA I/O board contains four

RS485 communications interfaces which are described on the following page.

These interfaces are fully software programmable in terms of their transmission

characteristic. The first RS232 Channel has the additional facility in that it can be

software configured on the direction of the RS232 interface, i.e. DCE or DTE, in this

application it is permanently configured as a DCE in order to connect to a controller’s

141 handset port.