Echelon LONWORKS PLT-22, User Manual

Page: 99 / 128

Unit Under Test
(UUT)
service pin
PLCA-22
To power
mains
packet detect LED
ISOLATOR
Recv
Isloated Power Line
C-band
Figure 7.6 Unintentional Output Noise Verification
If any of the signal strength LEDs, above the -72dB LEDs, flash, or the PKD LEDs
flashes more than once per minute, then excessive noise or interference is present.
This could be caused by one or more of the following sources:
• The UUT is generating unwanted noise internally. This is most often associated
with on-board switching power supplies. If the UUT includes a switching power
supply, verify that the power supply noise masks of Chapter 5 have been met.
• Power line communications signals present on the power input side of the isolator
are not sufficiently attenuated. Ensure that no other power line signaling equipment
is operating on the power mains when performing this test.
• The isolator is not completely isolating the test set-up from noise on the power
mains. Verify the effectiveness of the isolator as described earlier.
The source of this noise or interference must be identified and eliminated before
proceeding with verification testing.
Excessive Loading Verification
The procedure described in this section is used to determine if the receive mode
impedance of the UUT is greater than approximately 100 Ω at 132kHz (as it should
be). A receive mode impedance of less than 100 Ω could cause excessive signal
attenuation resulting in impaired reception by both the UUT and its neighboring
L
ON
W
ORKS
PLT-22 Transceiver User’s Guide 7-7