Question:
How do I use the PLC Signal Strength Test Set?
Answer:
The PLC test set is a very handy and easy to use
device for troubleshooting communications problems. However, it must be used
properly to gather valid signal strength information. The good news is that the
test procedure is really very simple when it is done systematically. Follow
these simple steps to get valid signal strength information:
·
Place
the greenhouse’s critical systems under manual control so that the GEM3 system
can be shut down safely for ten minutes or more.
·
Shut
down the GEM3 program by typing <Alt>, then <Q> to quit DESQview,
then <Y> for yes. This will cause the program to stop polling sensors and
devices in the greenhouse.
·
Go
to the Translator Unit and turn its power OFF. Now find the S4 strap that is
located in the upper left-hand corner of the circuit board. Install a special
shorting strap over the left-hand 3 pins of S4. (See Figure 1 at the end of
this document) A shorting strap fixture is available from Q-Com (one should be
sent with the tester). When you turn the power on again the Translator should
begin to transmit a continuous signal on the powerline throughout the GEM3
system for testing purposes.
·
Go
to all of your sensor units throughout the greenhouse and measure the strength
of the signal arriving from the Translator by plugging in the test set near the
sensor (see note below) and turning the knob to higher and higher levels until
the light goes out. Turn the knob back one setting and verify that the light
comes on and then record this signal level and location (a sample chart is
included at the end of this document). Do this at all sensors where
communications have been suspect.
i Please Note: For this signal reading to be valid, you MUST have your tester attached to the same phase as the sensor unit you are testing.
·
Now
go back to the Translator and remove the strapping fixture (remember to turn
off the power while working inside the box). When you turn the power back ON,
the translator should no longer send a continuous PLC signal, but return to
normal operating mode.
·
Go
to any suspect sensor unit, turn off the power, and strap out the top 3 pins of
JP1 (located on the left edge of the motherboard, just below the little green
light). When the power is restored, this will cause this particular sensor to
transmit its full strength signal continuously back to the translator unit.
(See Figure 2) Go to an outlet in the area of the translator that you are sure
is connected to one of the phases coupled to the translator unit (see note
below) and plug in the test set. Repeat the process described in step #3 to
record the signal level for this sensor. Remove the strap and then repeat this
test for any or all sensors in the system that you feel may be experiencing
communication difficulties.
i Please Note: The signal arriving back at the translator from the sensor unit is arriving on one particular phase. In a multi-phase system (like 220 single-phase - this name is misleading, there are actually 2 phases to neutral, or 208 3-phase) the sensor signal will come back very weak on the phases that are not powering the sensor unit. Therefore, you should connect your test set to all available phases and use the highest reading on your test chart.
·
Remove
all strapping fixtures from any sensor or translator in the system. This will
make the system ‘quiet’ as long as the GEM3 program is still shut down. Now you
can go to any part of the system where you were experiencing problems and
record ‘noise’ levels. Do this the same way you did for signal testing; by
turning the knob down (usually to very low settings) until the light on the
tester illuminates and then up again until it extinguishes. Go back down one
notch and verify that the light comes on again, then record this level as
‘Noise’ on your list for this location.
·
Restart
the GEM3 program as soon as you are finished with the testing and return all
controls to automatic operation.
·
Send
your list of recorded signal and noise measurements, listed by location, to
Q-Com for analysis. A sketch of the layout and the locations of the translator
and sensor units would also be helpful in resolving the problem.
With this information, we should be able to help you
find the source of your problem very quickly.
Sample Test
Chart
Note: In this test procedure, the sensor is the
important element, whether in the translator-testing phase, or the
sensor-testing phase. In the translator-testing phase, you will be located at
or near a particular sensor, and that location should be recorded in first
column. In the sensor-test phase, a particular sensor will be transmitting and
you will be testing at the translator for signal strength. So again, the sensor
location is the key. That is why there is a column for each testing phase
beside each sensor location listed in column 1 of the chart.
In the noise testing phase there is a special line
just for the translator, so you can record the noise level in its area with the
GEM3 system shut down.
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Sensor Location Tested |
Translator Test |
Sensor Test Phase |
Noise Test Phase |
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Translator |
---------N/A---------- |
------------N/A----------- |
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If you need further help or information, give our Customer Service Department a call at (949) 833-1000 or (904) 963-5851. Or, visit our web site @ www.qcomcorp.com for further technical support.
