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Terminated

Unterminated

The reason for this is that with high speed digital data, it is critical that the electrical energy that runs

down the wires is absorbed at the end and does not "bounce back" down the wire and cause

interference with other data coming down. To exactly absorb all the energy coming down a wire, the

wire must be ended at the last device in the chain with a resistor, which has value that equals the

characteristic impedance of the wire. Each collector unit is equipped with such a resistor that is

connected when the switch is in the TERMINATED position.

4.5.3 Power-up Test

Collectors are provided with a 24V power supply that

must

always be used for each collector,

providing local operating power. No other power supply is adequate to power collectors. To ensure

that the power supplies do not pull out by their own weight, either mount the power strip outlet side up

or use wire ties to hold the power supply in place.

When the collector wiring and isolation have been verified and the cable connection between the

concentrator and the collector has been tested and found correct, the next step is to apply power to the

collector and check the sensor connections for the correct voltages.

 To test sensor voltage

Once power has been applied to the collector, a voltmeter check should be made of the sensors on

the punch-down block to verify that they are connected correctly.

Set the voltmeter or multimeter to a 20-volt range.

Apply the probes to each sensor connection on the punch-down block.

If the reading is:

For: (Sensor type)

Then:

Approximately 18

volts

RF only the sensor is wired correctly.

<14 volts IR and RF

There is radio frequency or electromagnetic

interference.

Approximately 16

volts

IR only the sensor is wired correctly.

Approximately 20

volts

IR and RF

there is no sensor connected to this pair or the

wiring to the sensor is open.

Power supply may

become

disconnected if

power strip is

mounted sideways.

If the power strip is

mounted plug side

up, the power

supply will be firmly

seated.