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Appendix "C"
– TESTING PROCEDURE
TESTING PROCEDURE OF THE 2W SYSTEM
The 2W interface has three main functions:
1. Supplying energy to all the RTUs in the system.
2. Scanning all the RTUs second by second.
3. Exchanging information with the DREAM second by second.
The 2 wired cable originating from the 2W interface and arriving to all the RTUs, carries both
the energy and the communication to the RTUs. Due to the variable nature of the signal
carried by the 2W line, it cannot be measured by a voltmeter, not as a DC voltage and not as
an AC voltage. The testing procedure described herewith helps us to overcome this obstacle
and enables us to differentiate between a normal system and a system with problems.
Putting the 2W interface into SPECIAL TEST MODE:
set the address switch of the
interface to 000000 and press the RESET button of the interface. As a result the red led
indicating the communication between the DREAM and the interface stops blinking and
remains constantly ON.
Checking the supply voltage:
test the supply of 12v DC to the interface.
Checking the output voltage of the interface:
check the existence of 36v DC at the
terminals where the 2 wired line is connected to the interface.
Measuring
the “load free” consumption of the interface:
disconnect the 2 wired line from
the interface. Connect an Ampere meter in the range of 200 or 500 mA between the positive
12v wire feeding the system and the +12v terminal on the interface board where the wire is
supposed to be connected. This way we are measuring the consumption of the interface
itself. It should be around 115-120 mA.
Measuring the contribution of the cable to the consumption of the interface:
unplug all
the RTUs from the 2 wired line and reconnect the 2 wired line back to the interface. At this
stage the measured consumption of the interface may increase due to possible leakage of the
cable. The consumption contributed by the cable depends on it’s length, thickness of the
wires and the quality of the coating of the wires. Up to 20-30 mA may be considered
reasonable.
Measuring the contribution of the RTUs to the consumption of the interface:
The
contribution of each RTU to the consumption of the interface should be about 1.5-2.2 mA.
Plug the RTUs back to the 2 wired line one by one and make sure that the consumption
grows by 2.2 x N, where N represents the number of RTUs in the system. If the consumption
is significantly higher it means that some of the RTUs are consuming too much.
Measuring the consumption of the RTUs in the field:
the consumption of each RTU can
be measured in the field by the “2W tester” or by a regular Ampere meter. For measuring by
the tester, see the instructions of
the tester’s manual. For measuring by an Ampere meter,
the inte
rface 2W must be in “SPECIAL TEST MODE” (see above), in this case the interface is
feeding the line with 36v DC. However a voltage drop along the cable down to 20v DC is still
acceptable. The individual consumption of the RTU can be measured by inserting the Ampere
meter (range of 10-20 mA) in series with one of the 2W wires. A normal result will be 0.75 mA
for the modular RTU and 0.5 mA for the compact RTU.
Exiting SPECIAL TEST MODE :
In order to return to normal operation mode set the address
switch of
the 2w interface to it’s correct address and push it’s RESET button. As a result the
red led indicating the communication between the DREAM and the interface will start blinking,
a short blink each second.
