NOTE
It is very important to make sure that the 24 V feed in the external insulation unit
is not connected to one of the communication outlets. If it does not have 100%
insulation against the 24 V feed, disturbances and grounding currents from the 0 V on
the 24 V side disrupt the communication.
Using this type of unit solves one problem but creates a larger problem! A
substandard installation may work now, but problems may arise when other devices
are connected.
7.7. Cable and Bus Termination RS-485
• If maximum transfer distance and maximum transfer speed is needed, shielded and twisted pair
cable should be used. The mutual capacitance may not exceed 52.5 pF/m, and the cable area
should be at least 0.25 mm
2
(AWG 24).
• 0 V, the reference voltage for communication should be included in the cabling. With two-way
communication use two pairs; one pair for communication and one pair for 0 V.
• The shield must be grounded at one end. The other end is usually grounded, but with longer
distances or when there is a difference in the ground potential, the shield should be connected to
the ground via 0.1 μF / 250 V film capacitor to prevent ground current in the braided shield. Some
manufacturers recommend that the shield be grounded at each node. Various manufacturers have
different systems for bus termination.
Depending on the recipients’ design, the bus wires may be on the same level or require pull-up
or pull-down to ensure that no faulty signals are detected when the bus is in resting mode (all
transmitters are disconnected).
7.8. USB Flash Drive
The USB port, or ports, are of 2.0 standard and support FAT16, FAT32 and exFAT file systems for USB
flash drives (option, sold separately).
Size limitations for file systems:
• FAT16: up to 2 GB
• FAT32: up to 32 GB
• exFAT: up to 2 TB
7.9. Image Sticking
When utilizing TFT LCD HMI panels in applications where a fixed or partially fixed image remains
displayed on the screen for extended periods of time, users may experience a phenomenon referred
to by the LCD industry as Image Sticking. Image sticking, sometimes also called “image retention” or
“ghosting", is a phenomenon where a faint outline of a previously displayed image remains visible on
the screen when the image is changed.
Image sticking can be caused by:
• Static images
• No screensaver
• Sharp contrast transition (e.g. black/white)
• High ambient temperatures
How Image sticking can be avoided or reduced:
Additional Installation Tips
2023-09 28 Beijer Electronics, MAEN330
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